Written by Kiara Aleksy T. Paglinawan

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

Skeletal muscle is a striated, multinucleated, and voluntary type of muscle tissue. Out of the three types of muscle tissue, skeletal muscle is the most abundant in the human body. It comprises about 30% to 40% of your body mass, with males having more than females.

They connect to bones directly or through tendons, which are connective tissues. They are responsible for a variety of functions. Skeletal muscles produce voluntary movements, meaning you control how and when they work. They consist of flexible fibers that contract, which allows the muscles to move bones.

This tissue has long, cylindrical muscle fibers. These fibers group into bundles known as fascicles. Each muscle fiber contains myofibrils that consist of repeating sarcomeres.

Sarcomeres are the functional units of contraction, consisting of actin and myosin filaments. These microscopic structures give skeletal muscle its striated appearance under a microscope.

A connective tissue layer called the epimysium surrounds the entire muscle. The perimysium encloses each fascicle, while the endomysium wraps around individual muscle fibers.

This structured design helps with efficient contraction and force transmission. It also protects your muscles during physical activity.

Skeletal muscles also have special properties that help them do their jobs well. These properties make movement smooth, fast, and controlled.

Properties of skeletal muscle:

1. Extensibility. Muscles can stretch without damaging themselves. This allows your body to move in many directions.
2. Elasticity. Muscles can stretch or shorten, then return to their normal shape and size.
3. Excitability. Muscles respond to signals from the brain and nerves. This is how you control movement.
4. Contractility. When muscles receive signals, they shorten or contract. This action pulls on bones and creates movement.

These four properties work together every time you move. When you extend your arm to grab something up, your muscles first stretch. When you grip the object, your muscles contract. Afterward, they return to their original shape, ready for the next action.

These abilities are not only useful for motion. They also help keep balance, protect joints, and hold your posture. Without these muscle traits, it would be difficult to walk, sit, or even smile.

Skeletal muscles fall into two main types: red and white. This classification is based on their function and appearance under a microscope.

1. Red Muscles (Slow-Twitch Fibers)

These muscles get their red color from myoglobin, a protein that stores oxygen. They contain many mitochondria, the energy powerhouse of the cell. These help the muscles work for a long time without getting tired.

Red muscles are;

• smaller in size
• rich in oxygen and blood supply
• built for endurance and steady activity

2. White Muscles (Fast-Twitch Fibers):

White muscles have less myoglobin and fewer mitochondria. They are bigger in size and work better for fast, powerful actions.

White muscles are;

• larger in size
• quick to act but get tired easily
• used for strength and speed

You use white muscles when sprinting, jumping, or lifting heavy objects. These muscles work fast but need more time to rest.

Both red and white muscles are important. Most of your skeletal muscles contain a mix of both types. The exact amount depends on your genetics and the kind of activity you often do. Athletes who run marathons usually have more red fibers. Sprinters or weightlifters tend to have more white fibers.

Knowing these muscle types also helps in exercise and health. Training can make your muscles stronger or increase their endurance. Regular exercise won’t change one muscle type into another, but it helps your muscles work better.

Skeletal muscles are strong, flexible, and responsive. Their properties help them stretch, contract, and return to shape. Their types support both steady movements and sudden actions.

What are the characteristics of skeletal muscle?

Skeletal muscles typically connect to bones through tendons. These connections help generate movement whenever your muscles contract. Tendons act as strong cords that conduct force to the skeleton.

Skeletal muscles are long and cylindrical in shape. They are often called muscle fibers and can extend the full length of a muscle. Connective tissues bundle these cells together.

Each muscle cell has many nuclei. This allows the cell to produce large amounts of proteins. Enough amount needed for contraction and repair.

You can see striations when viewed under a microscope. Striations are visible as light and dark bands. These bands come from the arrangement of actin and myosin filaments in sarcomeres.

Skeletal muscles contract through a well-known process. The sliding filament theory is the mechanism by which muscle contracts at the cellular level. In this process, actin and myosin filaments slide past each other to shorten the muscle fiber.

Skeletal muscles are under voluntary control. This means you can move them in a conscious state, unlike cardiac or smooth muscle. Movements like walking, running, lifting, and facial expressions rely on these muscles.

Each muscle cell has a membrane called the sarcolemma. This membrane keeps the cell’s shape and sends signals that trigger muscle contraction.

Muscle cells store energy and oxygen using specialized structures. Glycosomes store glycogen for energy. Myoglobin holds oxygen for use during activity.

Inside the muscle fiber, you’ll find myofibrils that carry out contractions. These myofibrils contain sarcomeres, the smallest units of muscle contraction.

Muscle cells also have sarcoplasmic reticulum dedicated to calcium ions (Ca2+) handling. This specialized form releases calcium when the muscle needs to contract. It pumps calcium back in when the muscle relaxes.

T-tubules run deep into the muscle fiber, enhancing cellular communication. Transverse tubules are invaginations of the sarcolemma. They bring the sarcolemma very close to the sarcoplasmic reticulum. This setup helps the rapid spread of Ca2+ ions. This synchronized release allows muscles to contract with more force.

What is the function of skeletal tissue?

Skeletal muscles are a vital part of your musculoskeletal system.

These muscles pull on bones to create movement. Every time you walk, lift, or reach, your skeletal muscles work to move your body. They contract with force, allowing fast and precise actions.

These muscles also keep your body in position. Even when you’re standing still, they contract to support your posture. Without them, your spine and joints would collapse under your weight.

Skeletal muscles help control body temperature. When they contract, they release heat as a by-product. This keeps your body warm, especially during cold conditions.

Muscles also play a role in breathing. The diaphragm, which is a skeletal muscle, moves air in and out of your lungs. Other muscles in your chest assist with deeper or forced breathing.

They support facial expressions and speech. Tiny muscles in your face allow you to smile, frown, or speak clearly. Voluntary skeletal muscle contractions control each movement.

These muscles assist in swallowing and digestion. Skeletal muscles are found at the openings of internal tracts. They control the voluntary movement of substances like food, urine, and stool. This makes swallowing, urination, and defecation possible under conscious control.

Other functions include tasks that are seldom discussed but hold equal importance:

Skeletal muscle releases myokines during contraction. Myokines are proteins made by muscle cells when you move. They help your body respond to physical activity. They also support growth, healing, and disease protection.

Myokines affect energy metabolism and inflammation. They play a role in the development of metabolic diseases like type 2 diabetes. Some myokines improve insulin sensitivity and glucose use. They help regulate both sugar and fat metabolism.

Skeletal muscle supports energy balance in your body. It stores sugar and fat for later use. This keeps energy levels stable during rest or movement.

Where is skeletal muscle found?

You can find skeletal muscles throughout your body. They connect to bones using tendons and pull on them to create motion. This includes both large and small movements across joints.

In the head and neck, skeletal muscles help move the eyes, chew food, and create facial expressions. Muscles like the frontalis and orbicularis oris help you express emotions. The sternocleidomastoid turns and flexes your neck.

The trunk houses muscles like the intercostals and diaphragm, which assist in breathing. Back muscles such as the erector spinae stabilize your spine and support posture.

Your upper limbs have muscles like the biceps brachii, triceps brachii, and deltoid. They help you lift, push, and pull. The lower limbs have the quadriceps femoris, hamstrings, and gastrocnemius. They help you walk, run, and jump.

Skeletal muscles play roles in breathing, locomotion, and communication. They allow you to sit upright, walk, talk, and even smile. Their broad distribution is essential for both function and form.

Do skeletal muscles protect internal organs?

Yes, skeletal muscles protect internal organs. These muscles do more than move your body. They provide support and absorb physical impacts.

Your striated muscles in the abdomen, chest, and pelvis create layers. These layers protect the soft tissues underneath.

Your abdominal area has muscles like the rectus abdominis, obliques, and transversus abdominis. These muscles help protect the stomach, liver, intestines, and kidneys. These muscles hold the organs in place and absorb shocks from outside forces. They also increase abdominal pressure to help with stability and posture.

In the chest, the pectoralis major and the muscles between the ribs help protect the heart and lungs. They form a muscular layer beneath the ribs, adding another level of support. These muscles also aid in breathing and upper limb movement.

In the pelvic area, skeletal muscles like the levator ani form the pelvic floor. They support organs such as the bladder, uterus, and rectum. Without these muscles, organs would shift or prolapse over time.

Muscles respond quickly to protect the body. For example, when you sense danger, muscles tense up to shield vital areas. This shows how protection is an active role, not a mere side effect.

How does skeletal muscle tissue contribute to body temperature?

Skeletal muscles help keep the body in balance by generating heat.

Muscle contractions need energy in the form of ATP. When ATP breaks down, it produces heat. This is especially noticeable during exercise. As muscles move, body temperature rises. In extreme cold, shivering causes random muscle contractions, which also generate heat.

As your muscles work harder, more heat builds up. This is why your body feels warmer and you start sweating during physical activity. The heat keeps your internal environment stable even in cold surroundings.

When you’re cold, your body reacts by making muscles contract rapidly. This reaction is called shivering.

These small movements create heat and help raise your body temperature.

Yet, too much heat from muscle contractions can be dangerous. There is a rare condition called malignant hyperthermia. It happens in people who are genetically sensitive to certain anesthesia drugs.

In these individuals, skeletal muscles release too much calcium. This leads to sustained contractions and extreme heat buildup. Because the person is asleep under anesthesia, they cannot cool themselves.

Without quick treatment, their body temperature rises too high and may cause death. That’s why doctors ask about family history before surgery. Early awareness can prevent this medical emergency.

Skeletal muscle is not only for movement. It is also essential in keeping your temperature balanced.

Which food will increase body muscle?

Don’t get distracted by the protein powder propaganda. You can get plenty of muscle-building nutrients by adding the right foods to your diet. To build muscle, you must eat the right foods. Good nutrition gives you the energy you need to thrive.

It becomes important to consume foods that help you build muscle mass. This includes protein-rich foods, along with essential carbs and fats.

Here are some foods that contribute to natural muscle building:

1. Eggs: eggs are the perfect protein source. They contain healthy fats and key nutrients like vitamin B and choline. Eggs contain large amounts of the amino acid leucine. This is key for helping your body make protein, which boosts muscle gain.

• Lean beef: beef is packed with high-quality protein, B vitamins, minerals, and creatine. It also contains saturated fats that help to maintain healthy testosterone levels. It is an androgenic hormone that is very important for building muscle mass.

• Chicken breast: it is a viable source of protein as chicken contains the highest amount of it. Each 3-ounce (85-g) serving contains about 26.7 g of high-quality protein. A 2018 study found that eating chicken after exercise can aid in fat loss. It may also boost muscle mass and strength.

• Salmon: it is great for your health and is an excellent choice for building muscle. A 3-ounce (85-g) serving of salmon has about 17 g of protein, 1.5 g of omega-3 fatty acids, and several key B vitamins.

• Greek yogurt: it is a mixture of fast-digesting whey protein and slow-digesting casein. Greek yogurt has more protein (20 g per serving) compared to regular yogurt (16 g per serving).

• Quinoa: you also need energy for your activities. Foods with carbohydrates can help provide this energy. Cooked quinoa has about 40 g of carbs in a cup (185 g). It also offers 8 g of protein, 5 g of fiber, and good amounts of magnesium and phosphorus. Magnesium is important for your muscles and nerves.

Skeletal muscle is more than a tissue of movement. It is a complex, dynamic system essential for human life. It moves, protects, warms, and even heals. Understanding its workings reveals its pivotal role in maintaining strength and balance.

References:

Professional,        C.         C.         M.         (2025,        April       17).        Skeletal       muscle.               Cleveland       Clinic. https://my.clevelandclinic.org/health/body/21787-skeletal-muscle

Rossi, D., Pierantozzi, E., Amadsun, D. O., Buonocore, S., Rubino, E. M., & Sorrentino, V. (2022). The sarcoplasmic reticulum of skeletal muscle cells: a labyrinth of membrane contact sites. Biomolecules, 12(4),

488. https://doi.org/10.3390/biom12040488

Wikipedia                contributors.                (2025,                March               16).                T-tubule.                  Wikipedia. https://en.wikipedia.org/wiki/T-tubule#:~:text=As%20T%2Dtubules%20bring%20the,cells%20to%20contr act%20more%20forcefully

Balakrishnan, R., & Thurmond, D. C. (2022). Mechanisms by which skeletal muscle myokines ameliorate insulin resistance. International Journal of Molecular Sciences, 23(9), 4636. https://doi.org/10.3390/ijms23094636

Iizuka, K., Machida, T., & Hirafuji, M. (2014). Skeletal muscle is an endocrine organ. Journal of Pharmacological Sciences, 125(2), 125–131. https://doi.org/10.1254/jphs.14r02cp

Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J. E., Womble, M., & DeSaix, P. (2022, April 20). 10.2 Skeletal Muscle – Anatomy and Physiology 2E | OpenStax. https://openstax.org/books/anatomy-and-physiology-2e/pages/10-2-skeletal-muscle

Admin. (2021, March 8). Skeletal muscle. BYJUS. https://byjus.com/biology/skeletal-muscle/

Upper           limb           muscles           and           movements.           (2023,           November           13).       Kenhub. https://www.kenhub.com/en/library/anatomy/upper-limb-muscles-and-movements

Lower                   limb                   anatomy.                   (2023,                  September                  11).               Kenhub. https://www.kenhub.com/en/library/anatomy/lower-extremity-anatomy

Facial muscles. (2023, November 21). Kenhub. https://www.kenhub.com/en/library/anatomy/the-facial-muscles

Sternocleidomastoid                     muscle.                    (2023,                    October                    30).                                        Kenhub. https://www.kenhub.com/en/library/anatomy/sternocleidomastoid-muscle

Erector                  spinae                  muscles.                  (2023,                  November                  3).                Kenhub. https://www.kenhub.com/en/library/anatomy/erector-spinae-muscles

Dave, H. D., Shook, M., & Varacallo, M. A. (2023, August 28). Anatomy, skeletal muscle. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK537236/

CCCOnline.                   (n.d.).                   Muscular                   system                   homeostasis.                         Pressbooks. https://pressbooks.ccconline.org/bio106/chapter/muscular-system-homeostasis/

Sharp, M. H., Lowery, R. P., Shields, K. A., Lane, J. R., Gray, J. L., Partl, J. M., Hayes, D. W., Wilson, G. J., Hollmer, C. A., Minivich, J. R., & Wilson, J. M. (2017). The effects of beef, chicken, or whey protein after workout on body composition and muscle performance. The Journal of Strength and Conditioning Research, 32(8), 2233–2242. https://doi.org/10.1519/jsc.0000000000001936 Cissn, G. T. P. C. (2024, February 15). 26 foods to eat to gain muscle. Healthline. https://www.healthline.com/nutrition/26-muscle-building-foods#muscle-building-foods

Written by Gynne Ross Q. Ancheta

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

Have you ever wondered what our hair is composed of? Let me take you back to the basics! It is composed of a protein called keratin, a fibrous structural protein.

In the hustle and bustle of life, we tend to get overwhelmed by chores and issues and forget to stop for a moment to enjoy the little marvels that abound. But occasionally, in the simplest of things—such as a single strand of hair—we see beauty, intricacy, and even a lesson in slowing down.

Is it only found in your hair? No. Keratin is also found in your skin and nails. It provides strength, structure, and resilience to hair strands.

You may ask, what microscopic layers make up the hair?

1. Cuticle – the outermost layer. It is made of overlapping cells that protect the inner layers. It is responsible for the hair’s shine and smoothness and is a barrier against physical and chemical damage.
2. Cortex – the middle layer. It contains keratin and melanin. This layer provides strength and elasticity. This layer determines the texture and curl pattern of the hair.
3. Medulla – the innermost layer. It is sometimes absent in finer hair. It has a more spongy structure. It plays a role in the hair’s structure and flexibility.

The keratin comprises amino acids, primarily cysteine, which form strong disulfide bonds. These bonds are what give hair its strength and shape. Also, hair contains small amounts of lipids, water, and minerals.

What are the characteristics of the hair? Let me take you on a more profound look! Your hair has several characteristics:

1. Color can vary from black, brown, blonde, gray, or white. It is determined by the amount and type of melanin in the hair.
2. Length refers to how long the strands are. It can vary from very short to extremely long. However, it depends on how much it has grown and whether it has been cut.
3. Texture describes the feel and appearance of the hair. It can be fine, medium, or coarse. It also refers to whether the hair is straight, wavy, or curly.
4. Thickness refers to the density of the hair strands on the scalp. You may have thick, full hair, while others may have thin or sparse hair.
5. Shape can be round, oval, or flat, influencing whether the hair is straight, wavy, or curly.
6. Condition describes the health of the hair. Healthy hair is shiny, smooth, and strong, while damaged hair is dry, brittle, or frizzy.
7. Style refers to how the hair is arranged or groomed. It could be natural, braided, tied up, or styled with tools and products.

It is important to note that each characteristic can vary from person to person.

Here is a fun fact for you! Your hair characteristics can change due to genetics, age, and hair care practices.

What kind of cells are in hair?

The protein keratin is produced by specialized cells called keratinocytes. These cells originate in the hair follicle, located in the dermis, the middle layer of the skin.

Here is how it works:

1. Hair follicle and keratinocytes – The hair follicle is a tiny structure in the skin where hair grows. Inside the follicle, keratinocytes multiply and produce keratin, a tough and fibrous protein that gives hair strength and structure.
2. Hair Shaft Formation – As keratinocytes move upward through the follicle, they die and become part of the hair shaft. When the hair emerges from the skin, it is made of dead keratinized cells. This is why the visible part of your hair is not “alive.”
3. Melanocytes – Another type of cell in the hair follicle is the melanocyte. These cells produce melanin, the pigment that gives hair its color. The amount and type of melanin determine whether your hair is black, brown, blonde, or red.

The primary cells in hair are keratinocytes (which produce keratin) and melanocytes (which provide pigment). Once the hair grows out of the follicle, it comprises dead keratinized cells.

If you are uncertain whether hair is a protein or a cell, here is a breakdown!

Hair is primarily made up of a protein called keratin, a fibrous structural protein found in nail and skin. It is responsible for the strength and structure to the hair strand.

Hair itself is not a living cell. The part of the hair you see (the shaft) is made of dead keratinized cells that have been pushed out of the hair follicle. The living part of the hair is in the follicle beneath the skin, where cells divide and grow to form the hair strand. So, while hair is not a cell, it is made of protein and originates from living cells in the follicle.

Is hair an organ or tissue?

Hair is considered a tissue, not an organ. Here’s why:

In biology, an organ is a structure of multiple types of tissues that work together to perform a specific, complex function. For example, the heart is an organ because it contains muscle, connective tissue, and nerve tissue, all working together to pump blood.

On the other hand, a tissue is a group of similar cells that perform a specific function. Hair comprises keratinized cells, specialized cells that produce keratin, a tough protein. These keratinized cells form a structure (the hair shaft) but don’t combine with other tissue types to create a complex organ.

Hair itself is just a single type of tissue. However, the hair follicle, the structure in the skin that produces hair, is more complex. The follicle contains multiple tissue types (epithelial, connective, and sometimes muscle tissue), so it could be considered part of an organ—the skin.

The hair itself is a tissue, not an organ, because it is made of one type of specialized cell and doesn’t have the complexity of an organ.

What part of the hair contains DNA?

Hair is made up of two main parts:

The shaft (the visible part above the skin) and the root (the part below the skin, inside the follicle). The shaft is made of keratin, a protein, and does not contain any DNA because it consists of dead cells. The root, however, is located within the hair follicle under the skin.

This is where living cells are present, and these cells contain DNA. Specifically, the DNA is found in the nucleus of the cells in the root. When hair is pulled out with the root attached, it often contains follicular tissue rich in DNA. This is why hair with the root is used in forensic investigations for DNA analysis.

FUN FACTS!

1. Hair is mainly made of keratin. This is the same protein that makes up your nails and the outer layer of your skin.
2. Hair grows fast. Hair is the second fastest-growing tissue in the human body, after bone marrow. It grows about 0.5 inches (1.25 cm) per month.
3. You have a lot of hair. The average person has about 100,000 to 150,000 hair strands on their scalp. Blondes tend to have the most hair, while redheads have the least.
4. Hair is strong. A single strand of hair can support up to 100 grams of weight. Combining all the hair on your head could support the weight of two elephants!
5. Hair is mostly water. About 25-30% of your hair’s weight is water. This is why it feels heavier when wet.
6. Hair color is determined by melanin. The amount and type of melanin in your hair determine its color. As you age, melanin production decreases, leading to gray or white hair.
7. Hair is dead. The visible part of your hair (the shaft) is made of dead cells. Only the root in the follicle under the skin contains living cells.
8. Hair can “feel” things. While hair itself doesn’t have nerves, the follicles are surrounded by nerve endings. This is why you can feel a light touch or movement on your hair.
9. Hair grows in cycles. Hair growth happens in three phases: anagen (growth phase), catagen (transition phase), and telogen (resting phase). About 85-90% of your hair is in the growth phase at any given time.
10. Hair can reveal your health. Hair can store information about your diet, drug use, and environmental exposure. This is why hair samples are sometimes used in forensic or medical testing.

Hair is more than just an aspect of our looks—it’s a remarkable structure made mainly of keratin, molded by   living   cells,   and shaped by   our   genetics, surroundings, and grooming habits. While the hair we see is dead, its roots are alive, secreting a tissue that mirrors our identity and gives us important clues about our health and way of life.

By learning about hair’s layers, structure, and microscopic characteristics, we appreciate a taken- for-granted aspect of life. So the next time you catch a glimpse of yourself in the mirror, remember—your hair has a tale of biology, toughness, and uniqueness.

As we’ve seen, hair isn’t just a mere styling subject. It’s a fantastic structure composed of keratin, molded by living cells, and affected by our biology, habits, and grooming. From its microscopic layers to its capacity to reflect our well-being, hair is an incredibly compelling testament to how even the most mundane aspects of our body contain monumental design and function.

So the next time life gets too much, remember: there’s worth in the fundamentals. In learning to see and appreciate even   the little things,   such as our   hair,   we find again a   sense of awe and appreciation for ourselves.

References:

Cleveland Clinic. (2022). Integumentary System. Cleveland Clinic; Cleveland Clinic. https://my.clevelandclinic.org/health/body/22827-integumentary-system

Elkins, Z. (n.d.). How does our hair contain DNA? Columbia Daily Tribune.

https://www.columbiatribune.com/story/lifestyle/family/2018/10/09/how-does-our- hair-contain/9605125007/

Kingsley, A. (2022, April 11). The Hair Structure. Https://Www.philipkingsley.co.uk/. https://www.philipkingsley.co.uk/hair-guide/hair-science/the-hair-structure.html

Magtiza, A. (2021, February 19). 2.2 Hair and Scalp Assessment. Opentextbc.ca; BCcampus. https://opentextbc.ca/haircolourforhairstylistslevel2/chapter/consultation/

Miller, C. (2020, September). 10.5 Hair. Pressbooks.pub; Thompson Rivers University. https://jwu.pressbooks.pub/humanbiology/chapter/12-5-hair/

Radhakrishnan, R. (2024, May 28). What Are the Four Types of Hair? MedicineNet. https://www.medicinenet.com/what_are_the_four_types_of_hair/article.htm

Specific Hair Follicular Keratinocyte Cell Types – CZ CELLxGENE CellGuide. (2025). Cellxgene Data Portal. https://cellxgene.cziscience.com/cellguide/CL:2000092

Watson, K. (2020, September 11). Is Hair Made of Dead Skin Cells? Healthline; Healthline Media. https://www.healthline.com/health/is-hair-dead#hair-growth

What Is Hair Made Of? – L’Oréal Paris. (n.d.). L’Oréal Paris.

https://www.lorealparisusa.com/beauty-magazine/hair-care/all-hair-types/what-is-hair- made-of-structure-anatomy

Wikipedia Contributors. (2019, June 3). Hair. Wikipedia; Wikimedia Foundation. https://en.wikipedia.org/wiki/Hair

Written by Danielle Bubole

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

The Golgi apparatus is the collecting, sorting, and packaging site of your cell. These packaged and sorted materials are then delivered to different sites for daily use. Thus, your Golgi apparatus’ main function is arranging collected cellular materials and putting them inside a vesicle to be delivered and used to different sites.

It’s either delivered to:

• The outside of your cell (through exocytosis)
• Endosomes make it into lysosomes
• Other cytoplasmic components

Exocytosis is the process of getting stuff outside of the cell.

Endocytosis is the process of getting stuff into the cell.

Now that you have a grasp of the overview of your Golgi apparatus’ function, let’s learn its main components.

Similar to your organ system which consists of collaborating organs, your Golgi apparatus also has its own components, these are:

• Cisternae – smooth membrane sac that forms the flat discs with swollen ends of your Golgi apparatus.
• Tubules – short interconnected structures protruding on the sides and also at a part of your Golgi apparatus that faces your cell membrane.
• Vesicles – sacs that develop from your tubules.
• Golgi vacuoles – large rounded sacs produced from a part of the Golgi apparatus that faces your cell membrane. Sometimes, it also acts as a lysosome.
• ERGIC – also called as Endoplasmic Reticulum Golgi Intermediate Compartment helps in the transport between your ER and Golgi apparatus.

Moving on to its networks, your Golgi apparatus is also divided into clusters of cisternae called:

• The convex cis face or the forming face (cis-Golgi Network)
• The concave trans face or the maturing face (trans-Golgi Network)

Forming face is what is near your endoplasmic reticulum and the primary site to receive the materials in the vesicles from your ER.

Maturing face is what is near your cell membrane and the site where the vesicles to be delivered in other sites are pinched out.

You must keep these in mind as we go into its process.

Remember that the proteins and lipids or the materials made by your ER are packaged in the form of vesicles. With the help of ERGIC, these vesicles will fuse with your forming face of your Golgi apparatus and move toward your maturing face. At the maturing face, the vesicle with the sorted and modified materials inside is pinched out to be delivered outside of the cell, fused with endosomes to make lysosomes, and delivered to other cytoplasmic components.

All in all, that is how your Golgi apparatus works. However, to know more let’s dive deeper!

What is the function of the Golgi vesicles?

Golgi vesicles are small sacs that develop from tubules. Your Golgi apparatus’ vesicles help the transport of materials from one place to another. It encloses it, acting like a barrier from other cytoplasmic components.

There are two types of Golgi vesicles, namely:

• smooth vesicles
• coated vesicles

Different types of Golgi vesicles also have specific different functions. Let’s take a look at what these two types have.

Smooth vesicles

• Does not have a protein coat
• Transport materials inside your Golgi apparatus, to the plasma membrane, and other organelles
• Your smooth vesicles include secretory vesicles and other Golgi transport vesicles

Examples of your smooth vesicles are:

• Secretory vesicles (those that release hormones and neurotransmitters)
  • Transport vesicles inside your Golgi apparatus
  • Lipid-containing vesicles
• Their release mechanism can be constitutive (constant release) or regulated (stimulus-dependent release)

Coated Vesicles

• Covered with a proteinaceous coat (COPI, COPII, clathrin)
• Helps in your sorting, packaging, and transport of materials by selecting specific molecules
• Your coated vesicles include COPI, COPII, and clathrin-coated vesicles:
  • COPI-coated vesicles: retrograde transport in Golgi; it helps return proteins that accidentally left the ER.
  • COPII-coated vesicles: ER to Golgi transport
  • Clathrin-coated vesicles: transport materials from your Golgi to the endosome, which also involved in endocytosis
• Your coat assists in the selection of materials and budding of your vesicle. It is also removed before fusing with the target site.

Therefore, your type of vesicle relies on what appearance it has, whether it is coated or not. If it is coated what type of protein coat is present?

What is the role of the Golgi body in secretion?

Golgi body or Golgi apparatus transports modified materials to different sites. It includes delivering materials inside a vesicle outside of the cell. Thus, this is what you can call an example of secretion.

Back to your knowledge of cells, your cells produce proteins. For example, your nerve cell produces neurotransmitters, pituitary cells produce peptide hormones, and beta cells secrete insulin.

What do these have in common? Your secretory vesicles

There are two types of secretion, namely:

• Constitutive secretion – vesicles from the mature face are sent to the cell’s membrane for continued secretion
• Regulated secretion – vesicles containing the materials for secretion remain on the cell’s surface and wait for the signal to be secreted.

Now that you are set with this information, let us look more at its process.

Imagine the pancreatic beta cell, in these beta cells vesicles are filled with your insulin that is then modified and pinched out as a vesicle from the mature face of your Golgi apparatus.

Vesicles containing the same materials will fuse forming larger secretory vesicles. Those vesicles that contain insulin build up in the cell and wait for a glucose signal to enter the cell.

Once the glucose arrives, it will start a complicated process that causes the release. In a sense, it is not freed up because of glucose itself but because of the complicated process caused by the presence of glucose.

The secretory vesicles that contain the materials, insulin, will move to the plasma membrane and release the materials to neighboring blood capillaries. This process along with regulated release is what you call exocytosis.

Your released insulin will now act as a regulator that stimulates others.

In summary, Golgi body forms the vesicle for the materials needed to be secreted outside the cell or transported to different cytoplasmic components.

Where is the Golgi apparatus located?

Your Golgi apparatus is a membrane-bound organelle found in eukaryotic cells. It is located near the endoplasmic reticulum and nucleus.

Essentially, Golgi apparatus works very often with your endoplasmic reticulum. The materials made by your ER are transported via the vesicles to your Golgi body then sorted, modified, and packed to deliver into different sites. This explains why the Golgi apparatus remains close to the endoplasmic reticulum.

Secretory cells, those cells that the major function is to secrete contain many Golgi apparatus, however, no matter how many of them, these are still located in close proximity to your ER.

If you get into detail:

• Convex cis face or the forming face – is located near the ER.
• Medial Section – is located in the middle of the forming face and maturing face.
• Concave trans face or the maturing face – is located far from the ER and much closer to the cell membrane compared to your forming face.

Note: this is not to be confused with the Golgi network. Your Golgi networks are two clusters of cisternae namely the cis-Golgi Network and trans-Golgi Network. While the Convex cis face or the forming face, the Medial Section, and the Concave trans face or the maturing face are the regions.

Cisternae is divided into networks that are composed of regions containing different components such as your cisternae, golgi tubules, golgi vesicles, golgi vacuoles, and ERGIC. In summary, your Golgi apparatus is located near your ER to facilitate efficient transport of materials from your ER to the forming face towards the maturing face through the medial section.

Your network’s location is dependent on its function such as to receive or to secrete vesicles.

What would happen to the life of a cell if there was no Golgi apparatus?

Your cells produce proteins. Nerve cell produces neurotransmitters, pituitary cells produce peptide hormones, and beta cells secrete insulin. These are all products of your Golgi apparatus’ work.

Golgi apparatus collects, sorts, and packages materials to be brought to different sites via vesicles. Many of your proteins are synthesized by ribosomes in the endoplasmic reticulum, these are transported to your forming face and then modified before the vesicle containing these materials is pinched out from the mature face of your Golgi apparatus.

Your vesicles containing the materials modified from your Golgi apparatus move and fuse to larger secretory vesicles containing the same materials. These build up until it is secreted. Your cells’ secretion via Golgi apparatus is very important because it stimulates other molecules, and in turn responds to them, contributing to the overall process of the body.

Aside from getting the materials outside of the cell, vesicles from the mature face are delivered to either the endosomes to form lysosomes and other cytoplasmic components.

Your Golgi apparatus, Endoplasmic reticulum, and endosomes work in harmony. ER produces vesicles containing the materials transported to the Golgi apparatus which is then modified. Your modified materials are delivered outside of the cell for extracellular needs or add up to the cell membrane, and they can be transported to the endosomes to help produce the lysosomes.

Lysosomes are your cells’ site of digestion. It contains digestive enzymes, specifically hydrolytic ones. It breaks down wasted or worn-out cell parts, destroys viruses and bacteria, and ultimately, performs cell death if a cell is beyond repair to eliminate unwanted cells.

Therefore, if your Golgi apparatus is absent in your cell, there will be no means of transportation for secreting materials outside of your cell or exocytosis, no production of lysosomes, and no delivery of needed materials to other cytoplasmic components.

All in all, your cell will eventually DIE!

Who discovered the Golgi apparatus?

Golgi apparatus was discovered by Camillo Golgi. He is an Italian cytologist who discovered Golgi apparatus in a nerve cell of an owl.

Studying the nervous tissue, Camillo established a staining technique. This technique is named reazione nera, which means “black reaction.” In the present, it is known as the Golgi Stain. His way of staining includes fixing the nervous tissue with potassium dichromate and bathing it with silver nitrate.

While studying neurons using his technique, he identified an “internal reticular apparatus” and then later on called the Golgi Apparatus.

Camillos’ finding of this structure was doubted by other scientists but then during the invention of your electron microscope, Golgi Apparatus was confirmed to be real.

His findings not only contributed to scientific innovation but also led many medical developments to emerge, particularly in cell biology, neuroscience, and disease and research.

What are some interesting facts about the Golgi apparatus?

Golgi contains about 1,000 different proteins in mammalian cells, however, only 200 of them have been identified as of now.

Having 1,000 different kinds of protein only suggests that a very small component can do so much such as:

• Glycosylation – helps in protein folding, protects proteins from damage, and enables cell signaling and communication. (Example: The difference in blood types is due to different glycosylation patterns on red blood cells.)
• Processing hormones and neuropeptides – most hormones and neurotransmitters function after it is cut and activated. (Example: Insulin is also processed by your Golgi apparatus, which is important for your blood sugar regulation and preventing diabetes.)
• Transporting and sorting proteins – transports your proteins to specific locations and avoids misplacement that can cause diseases. (Example: Genetic disorders like I-cell or the build-up of waste in the cell will happen if lysosomal enzymes are not sent to lysosomes.)
• Making and modifying lipids – Production of your lipids for cell membranes and signaling molecules. (Example: Your sphingolipids are made by your Golgi apparatus, this is important for brain function and nerve protection.)
• Moving ions and molecules across membranes – supports your cell balance and metabolism for cell survival. (Example: Wilson’s disease can occur if mutations in copper-transporting proteins happen. This is caused by the build-up of copper in the body.)
• Maintaining Golgi structure – it keeps your Golgi apparatus organized so materials can be processed correctly and delivered to where it is needed. (Example: Disruptions of your Golgi apparatus can cause cancer and neurodegenerative diseases.)
• Connecting to the cytoskeleton – helps in cell division, immune response, and nerve function. (Example: Movement of your Golgi apparatus is needed for the release of your immune cells to targeted directions, fighting infections.)

Therefore, your Golgi apparatus is as important as any organelle in your cell.

References

Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Molecular Biology of the Cell (4th ed.). Garland Science. ISBN: 0-8153-3218-1

Darshan classes. (2022, September 8). What would happen to the life of a cell if there was no Golgi apparatus? [Video]. YouTube. https://www.youtube.com/watch?v=VnWC2Co6g3I

Alberts, B., Bray, D., Hopkin, K., Johnson, A. D., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2013). Essential Cell Biology (4th ed.). Garland Science. ISBN: 978-0815344544.

Hua Z, Graham TR. The Golgi Apparatus. In: Madame Curie Bioscience Database [Internet]. Austin (TX): Landes Bioscience; 2000-2013. Available from: https://www.ncbi.nlm.nih.gov/books/NBK6268/

Joao’s Lab. (2023, June 16). Golgi apparatus: structure and function [Video]. YouTube. https://www.youtube.com/watch?v=Jn-1lB5jb6I

LearnCBSE. (2024, August 12). NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life. Learn CBSE.

Life Science Resources. (2013, August 24). Golgi Complex: its secretions [Video]. YouTube. https://www.youtube.com/watch?v=0VBuA6XeSGQ

Medicosis Perfectionalis. (2018, October 22). The Golgi Apparatus “the sorter” – Cell Biology and Histology [Video]. YouTube. https://www.youtube.com/watch?v=hQEUFmOPdAs

Ninja Nerd. (2023, February 24). Golgi Apparatus Structure & Function [Video]. YouTube. https://www.youtube.com/watch?v=TPgyv2411Xo

Practically. (2020, December 30). Practically’s concepts – Golgi apparatus – #LearnPractically [Video]. YouTube. https://www.youtube.com/watch?v=iA8hFSHS6Ho

The Editors of Encyclopaedia Britannica. (n.d.). How was the Golgi apparatus discovered? | Britannica. Encyclopedia Britannica. https://www.britannica.com/question/How-was-the-Golgi-apparatus-discovered

Written by Mary Margarethe R. Cuevas

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

The lysosome plays a crucial role in cellular survival. It acts as the cell’s garbage disposal system. It also breaks down macromolecules and recycles cellular components. They are always perceived as the degradative organelle of the cell.

We all know that cells are the basic building blocks of life. They are the smallest units of life. But, they also carry out all the functions needed to keep organisms alive. Inside the cell, it has even smaller parts that we call as organelles. These organelles all perform different functions for our cells to operate.

One organelle that we all know is the nucleus. It is the one that stores all our genetic information. But, there is also this one tiny organelle that will be the subject in this article. Scientists call it the garbage disposal system of the cell, but it does much more than that.

Recent studies realized that lysosomes take part in other cellular processes. They are also involved in the killing of cellular pathogens. These pathogens are organisms that can grow and reproduce inside a host. Lysosomes are also involved in lysosomal membrane repair.

Damaged lysosomal membrane leads to cytoplasm leakage. When this happens, it needs to be immediately repaired. But, if a cell becomes damaged beyond repair, it will undergo cell death. It repairs itself through self-death, or apoptosis. This mechanism is crucial to not harm the surrounding cells. The lysosome is responsible for this job.

These are only some of the important cell processes that involve the lysosomes. Without them to perform these functions, the effects to our body can be detrimental.

What is the role of lysosomes in health and disease?

Lysosomes play a vital role both in health and disease as the cell’s disposal and recycling system. All the time, we are ingesting bacteria. Yet, we don’t always get sick or infected. Though there may be good bacteria, there are bad ones as well.

One of the many things that kept us healthy from bacterial infections are the lysosomes. Cells will ingest the bacteria and send it into its lysosome for destruction. As of now, we all know about the breakdown and recycling function of lysosome. They are able to do this due to the enzymes present in it.

These enzymes, known as hydrolytic enzymes, break down large molecules into small molecules. Our body needs to break large molecules into smaller molecules to use it. If this breakdown does not occur, it can result in a Lysosomal Storage Disease. This causes the lysosome to lose its function and the “trash” inside it accumulates.

Small molecules can turn to large molecules. This also happens inside the lysosomes. Yet, sometimes they can’t get out of it because the transporters needed for it are missing. Additionally, lysosome functions as sensors. They can tell if a cell is healthy or not or if it is being attacked, and track energy levels.

What is the role of lysosomes in cell death?

When damage occurs to a cell, it undergoes a mechanism called apoptosis. This mechanism is done by the lysosome. It is a crucial step to remove unnecessary and broken cells. These cells may hinder an organism’s growth and development when not removed. What happens is that our cells will receive signals to undergo apoptosis.

The lysosomes will then release their enzymes to the cytosol. Its lysosomal membrane breaks down, allowing the release of cathepsins and other proteases. These released enzymes activate a series of events that will end up killing the cell. We call this process Lysosomal Membrane Permeabilization (LMP).

Moreover, lysosomes are also involved in other forms of regulated cell death. The extent of lysosomal damage determines the type of cell death occurring. If a cell experiences partial damage, it still may undergo apoptosis. Some cells though undergo complete rupture. This results in what we call Necrosis.

How do lysosomes protect themselves from getting degraded by the enzymes present inside them?

We now know that lysosomes contain enzymes with digestive and hydrolytic functions. This time, are we not curious as to how the lysosomes protect themselves from degrading? Lysosomes are able to protect themselves through several mechanisms:

• Membrane protection – The lysosomal membrane itself serves as a protective barrier. A lipid bilayer composes the membrane and can withstand an acidic environment. Inside the lysosome is acidic due to the enzymes inside it. This gives the membrane another function. It keeps on these enzymes inside the membrane.

• Acidic environment – The lysosomal enzymes are also known as acid hydrolases. The acidic conditions inside the lysosome (pH 4.5 – 5.0)  is what activates the enzymes. The cytosol on the other hand is in neutral pH (pH 7.2) which can inactivate the enzymes when released outside.

• Repair mechanisms – When a damage manifests to the lysosomal membrane, the cell can start repairing it. This mechanism will restore the membrane’s integrity and prevent enzyme leakage. The cell does this by recruiting proteins that can help patch or repair any damage.

Can humans survive without lysosomes?

You have now reached this part of the article. By this time, we should have a similar response to this question. Indeed, humans cannot survive without lysosomes. We learned that the lysosome plays a role in important cellular processes.

As the cell’s disposal and recycling system, they facilitate autophagy and endocytosis. Basically, it digests internal and external materials. Examples of these are degrading proteins into amino acids and carbohydrates into simple sugars.

We also discussed how lysosomes play a role in the immune response. It is the one who destroys the invading bacteria and viruses to your body. Phagocytic cells engulf pathogens and enclose them in phagosomes through autophagy. Fused with lysosomes, they form phagolysosomes and then degradation occurs.

Cases where cells can be damaged beyond repair is possible. When this happens, the damaged cell can affect other cells. To avoid this from happening, the cell resorts to initiating self-death. This is done by the lysosomes by releasing their enzymes that break down the cellular components.

What happens when a lysosome dies?

It is now a familiar knowledge that lysosomes face death. Now, we start to wonder what actually happens after they die. Some of it was already discussed in this article. But what happens next? Will they disappear? Do they lie around the cytosol? Can they restore back as lysosomes? We will start answering these questions one at a time.

• Lysosomal membrane permeabilization – What happens first when lysosomes die is their membrane permeabilizes. The enzymatic contents inside such cathepsins will leak into the cytosol.

• Release of hydrolytic enzymes – The released enzymes from the lysosome will begin a series of reactions that will lead to the cell’s death. These reactions can also activate apoptotic pathways that promote apoptosis or necrosis.

•  Cell death pathways – We must know that there are different types of cell death. The type varies depending on the amount of lysosomal leakage. Cell death can be through apoptosis or necrosis. When we say an apoptotic death, the leakage is more regulated. Moreover, necrotic death has extensive and uncontrolled leakage.

• Effect on cellular homeostasis – We learned that the lysosome lumen is acidic. This is due to the hydrolytic enzyme inside it that is active at acidic pH. Once the cytosol receives all these, it may trigger inflammatory responses. These responses  will then contribute to more damage to its surrounding cells.

• Potential recovery – Our cells have mechanisms to recover from moderate LMP. It is through a process called lysophagy. The damaged lysosomes are removed through autophagy. This helps restore cellular function and maintain homeostasis. Note that this can only happen if the damage is not severe.

What is the role of lysosomes in aging?

We will now dive into the last part of this discussion. What does lysosomes have to do with aging?

A scientist in the name of Meng Wang tried to study the secrets tolongevity. Living in a family where longevity seems to run in their blood, she was curious. Wang, together with her team, discovered anti-aging signals in roundworms. These signals came from the lysosome.

In the study, the team discovered that lysosomes trigger a chain reaction of messages. This happens when the lysosome produces a specific fatty acid called dihomo-gamma-linoleic acid. These reactions are then what causes the roundworm’s life span to prolong.

Worms only live for 20 to 25 days. But in their study, the worm’s lifespan increased by 17 days. Additionally, the anti-aging signal that caused this longevity came from a fat tissue. Yet, it was still detected by neurons and tissues elsewhere in the worm.

This study opened doors for other scientists. They wanted to learn more about the other functions the lysosome may have. As for Wang, she didn’t stop there. She believes that there’s still more to discover.

More about it

Just like Meng Wang, there are other scientists out there studying the lysosome. One example would be the study of Shou Wang and her colleagues from Baylor College of Medicine. In the study, they investigated the role of lysosomes in brain function and Alzheimer’s disease.

There is another study from the Tokai National Higher Education and Research System. It is the link between lysosomal and their focal adhesion to cancer cells. Research on cancer treatments has already started a long time ago. The possibility for lysosome as a new therapeutic treatment for cancer contributes to its medical relevance.

Conclusion

Despite their size, lysosomes proved themselves to be important. As I like to appreciate the role of lysosomes, I think of this analogy. Our cell is like a community and lysosomes are the garbage collectors. The garbage collectors only had one main job to do in our community.

But, what we fail to realize are the results of their work. They keep our community clean. We are also far from the risks of diseases. Trashes can contribute to floods if not thrown properly. Instead, they are reused and recycled to other materials. This is exactly what lysosomes do.

Lysosomes protect us from pathogens that cause diseases. They clean our cells by collecting the unused materials in it. Recycling them to materials that can be used by our body. Moreover, it monitors our energy levels. It maintains the cell’s health and responds to stress.

I hope that this article shows you how fascinating it is that we learn more about our body. The more that we learn about it, the more we get to appreciate all of its parts, even the tiny ones.

References:

‌And, E. (2025, January 16). Decoding the link between lysosomal activities and focal adhesions could aid cancer research. Phys.org. https://phys.org/news/2025-01-decoding-link-lysosomal-focal-adhesions.html

‌Aits, S., & Jaattela, M. (2013). Lysosomal cell death at a glance. Journal of Cell Science, 126(9), 1905–1912. https://doi.org/10.1242/jcs.091181

‌Bonam, S. R., Wang, F., & Muller, S. (2019). Lysosomes as a therapeutic target. Nature Reviews Drug Discovery, 18(12), 923–948. https://doi.org/10.1038/s41573-019-0036-1

‌Castro-Obregon, S. (2010). Lysosomes, Autophagy | Learn Science at Scitable. Nature.com. https://www.nature.com/scitable/topicpage/the-discovery-of-lysosomes-and-autophagy-14199828/

‌Cooper, G. M. (2000). Lysosomes. Nih.gov; Sinauer Associates. https://www.ncbi.nlm.nih.gov/books/NBK9953/

‌Corrotte, M., & Castro-Gomes, T. (2019). Lysosomes and plasma membrane repair. Current Topics in Membranes, 84, 1–16. https://doi.org/10.1016/bs.ctm.2019.08.001

‌Flunkert, S., & Tatjana Hirschmugl. (2023). How Lysosomes Keep Us Healthy. Frontiers for Young Minds, 11. https://doi.org/10.3389/frym.2023.1109280

‌Gahl, W. (2019). Lysosome. Genome.gov; National Human Genome Research Institute. https://www.genome.gov/genetics-glossary/Lysosome

‌Kavčič, N., Pegan, K., & Turk, B. (2017). Lysosomes in programmed cell death pathways: from initiators to amplifiers. Biological Chemistry, 398(3), 289–301. https://doi.org/10.1515/hsz-2016-0252

‌Pu, J., Guardia, C. M., Keren-Kaplan, T., & Bonifacino, J. S. (2016). Mechanisms and functions of lysosome positioning. Journal of Cell Science, 129(23), 4329–4339. https://doi.org/10.1242/jcs.196287

‌The Editors of Encyclopedia Britannica. (2018). Lysosome | biology. In Encyclopædia Britannica. https://www.britannica.com/science/lysosome

‌Understanding the Role of Lysosome in Brain Function and Alzheimer’s Disease. (2025, January 31). BrightFocus Foundation. https://www.brightfocus.org/grant/understanding-the-role-of-lysosome-in-brain-function-and-alzheimers-disease/

‌Zhu, S., Yao, R., Li, Y., Zhao, P., Ren, C., Du, X., & Yao, Y. (2020). Lysosomal quality control of cell fate: a novel therapeutic target for human diseases. Cell Death & Disease, 11(9). https://doi.org/10.1038/s41419-020-03032-5

Written by Lorraine V. Espina

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

What is the cytoskeleton and its function? The cytoskeleton is a complex and changing network of protein filaments and tubules. It exists in the cytoplasm of eukaryotic cells and some prokaryotic cells.

It is a key part of the cell’s structure. It supports the cell and helps with many important functions. The scaffold-like structure supports the cell’s shape. It helps with intracellular transport and cell movement, and it also plays a role in cell division.

Three primary types of filaments make up the cytoskeleton.

1. Microfilaments, also called actin filaments, are the thinnest filaments of the cytoskeleton. Subunits of actin protein compose these.

Cells require microfilaments for various activities:

• maintaining cell shape,
• cell movement, and
• muscle contraction.

Actin filaments are dynamic and may polymerize and depolymerize at a rapid pace to allow the cell to change its shape or move.

2. Intermediate Filaments: These filaments are thicker than microfilaments but thinner than microtubules. In a cell, these give the strength and support needed to handle tension and stress.

Intermediate filaments are stiffer and less dynamic as compared to microfilaments and microtubules. Common examples of intermediate filaments are keratin, vimentin, and desmin. These proteins support various types of cells.

3. Microtubules: These are hollow, cylindrical tubes made up of tubulin protein subunits.

Microtubules take part in numerous processes, which include:

• cell division (mitosis and meiosis),
• intracellular transport, and
• the structural integrity of the cell.

They make up the mitotic spindle during cell division. They also act as a “highway” for motor proteins like kinesins and dyneins, which transport cargo inside the cell.

The functions of the cytoskeleton categorize into several key areas:

• Keep Cell Shape: The cytoskeleton gives the cell a strong framework. This support helps the cell resist deformation when under stress.

• Motor proteins like kinesins and dyneins help move things inside the cell. They travel along microtubules, carrying vesicles, organelles, and other cargo.

• Cell Division: The cytoskeleton helps move chromosomes and split daughter cells in mitosis.

• Cell Motility: The cytoskeleton allows for the movement of the entire cell or parts of the cell. This is important in processes such as tissue development, immune responses, and wound healing.

• Signal Transduction: The cytoskeleton connects with signaling molecules. These molecules influence how cells respond to growth factors and other external signals.

The cytoskeleton is a flexible network. It provides support but also changes and adapts to help the cell meet the demands of its environment.

What is the origin of the cytoskeleton?

The origin of the cytoskeleton has a significant connection to the evolution of cellular life. Most scientists think the cytoskeleton formed early in life’s development on Earth. This likely happened around the same time simple prokaryotic cells, like bacteria, appeared.

The cytoskeleton likely started as a set of proteins. These proteins helped the cell keep its shape and supported movement.

Prokaryotic cells have simpler cytoskeletal elements. They include FtsZ, a protein similar to tubulin that helps with cell division. There’s also MreB, an actin-like protein that supports cell structure.

These ancient elements were much simpler than any eukaryotic cell. They served as the building blocks for more complex cellular systems that followed.

As eukaryotic cells evolved, they became more complex and larger. This growth needed better organization inside the cells. The cytoskeleton developed in these cells. It helps with shape and structure. It also allows the cell to divide, move, and transport materials.

Eukaryotic cells have more complex cytoskeletons than prokaryotes. The various types of filaments found in eukaryotes show what prokaryotes lack.

The evolution of a complex cytoskeleton in eukaryotes likely helped multicellularity arise. This change allowed cells to interact, grow, and take on specific tissue roles.

What can damage the cytoskeleton?

The cytoskeleton is an important structure, but it is susceptible to damage or disruption in several forms. Damage to the cytoskeletal component leads to many varied dysfunctional cellular problems.

The most common reasons leading to cytoskeletal damage include:

1. Mechanical Stress: There is mechanical stress due to the physical forces applied in the surrounding environment of a cell. For example, when tissues deform or cells change shape, the cytoskeleton stretches too much. Its parts can break or become disorganized

• Infectious Agents: Pathogens like viruses, bacteria, and parasites often attack the cytoskeleton. They do this to enter host cells or use the host cell for their needs. .

• Oxidative Stress: Reactive oxygen species come from cellular metabolism or environmental damage. They can harm cytoskeletal proteins.

Oxidative damage can harm cytoskeletal structures. This disruption weakens cell function and stability.

• Genetic Mutations: Changes in genes for cytoskeletal proteins can damage the cytoskeleton. This harms its structure and function. Mutations in the dystrophin gene can cause Duchenne muscular dystrophy.

Dystrophin is a protein that links the cytoskeleton to the cell membrane. This condition weakens muscle cells.

• Nutritional Deficiencies: Missing nutrients like vitamin C can weaken the cytoskeleton. Vitamin C is important in the synthesis of collagen, which supports the cytoskeleton in some tissues. A deficiency will make the cytoskeleton fragile and susceptible to damage.

What happens if the cytoskeleton is defective?

Cytoskeleton defects can harm the cell. They may lead to various functional problems. The various outcomes depend on the specific part that is faulty.

Some common effects of the defective cytoskeleton include the following:

• Loss of Cell Shape and Integrity: The cell might lose its shape, become distorted, or not maintain its structural integrity.

Defective actin filaments can cause cells to become rounded. This change affects their normal shape and can hurt their function.

• Impaired Cell Division: The cytoskeleton helps organize and separate chromosomes when cells divide. Defects in microtubules or the mitotic spindle cause aneuploidy. This means cells have an abnormal number of chromosomes.

It leads to cancer, genetic disorders, or cell death.

• Inability to Move or Migrate: Cells need cytoskeletal components to move. If these parts get damaged, cells can’t move well.

For example, immune cells like macrophages may not be able to move toward infection sites, impairing immune responses.

• Impaired tissue function occurs when cytoskeletal proteins in multicellular organisms malfunction. For example, if muscle fibers fail to contract, they become weak. This can lead to diseases like muscular dystrophy.

• Neurological Diseases: Neurons depend on the cytoskeleton for support. It helps move substances along their long axons.

Mutations in proteins such as tau and neurofilaments connect to neurodegenerative diseases. These include Alzheimer’s disease and Parkinson’s disease.

Which cells lack cytoskeleton?

Most cells have a cytoskeleton. It helps keep their shape. It also supports functions and aids in movement and division. However, there are a few exceptions where certain types of cells lack a cytoskeleton or have a very minimal one:

1. Prokaryotic Cells (Bacteria and Archaea): Prokaryotes, including bacteria and archaea, usually do not have the complex cytoskeleton of eukaryotic cells. They do have simpler proteins that help them maintain their shape and facilitate cellular processes such as division.

The FtsZ protein in bacteria acts like tubulin. It helps prokaryotic cells divide by forming a ring structure, ensuring proper cell division. Protein MreB, similar to actin, aids in keeping the shape of prokaryotic cells.

These structures are simpler than microfilaments, microtubules, and intermediate filaments in eukaryotes. Still, they perform similar basic functions.

• Red blood cells (RBCs) classify as eukaryotic. But they lack most of the usual cytoskeleton found in other cells. Mature RBCs lose their nuclei and most organelles as they mature. They have a small cytoskeleton made of spectrin and actin.

This configuration enables them to maintain their balloonlike biconcave shape. Their incompressibility through tiny capillaries is integral to their need for such a shape.

RBCs are different from other cells. They don’t rely on a complex cytoskeleton for structure or function. Their main job is to transport oxygen.

Most eukaryotic cells rely on their cytoskeleton for survival and function. Prokaryotes have simple cytoskeletal structures too, which help them perform essential cellular tasks.

What are the diseases associated with the cytoskeleton?

Cytoskeletons play a key role in keeping cells shaped, dividing, and transporting materials. When disruptions occur, they can lead to many diseases. A few of the more notable diseases related to defects in the cytoskeleton are:

• Cancer: The cytoskeleton guides cell division. When microtubules, actin, or intermediate filaments have issues, it causes uncontrolled growth. This is a key feature of cancer.

Microtubule abnormalities can cause mistakes in chromosome separation, leading to genetic instability. Mutations in actin and vimentin help cancer cells invade nearby tissues. Drugs like taxanes work on microtubules to stop cancer cell division.

• Muscular Dystrophies: Duchenne muscular dystrophy (DMD) happens when there isn’t enough dystrophin. This protein connects actin filaments to the cell membrane. Without it, muscles weaken and waste away.

This causes trouble walking and can lead to losing mobility. Other muscular dystrophies, like limb-girdle muscular dystrophy, involve similar cytoskeletal protein mutations.

• Neurodegenerative Diseases: Alzheimer’s, Parkinson’s, and ALS (Amyotrophic Lateral Sclerosis) affect the cytoskeleton in neurons. In Alzheimer’s, tau proteins disrupt microtubules, causing cell death.

In Parkinson’s, problems with microtubules hinder the movement of key parts. This is especially true in dopamine-producing neurons.

• Ciliopathies: Primary Ciliary Dyskinesia (PCD) and others result from microtubule defects of cilia. The body compromises respiratory and fertility functions.
• Situs inversus is a condition linked to Kartagener’s syndrome. This syndrome is a form of PCD. In situs inversus, the body mirrors all internal organs.
• Epidermolysis Bullosa (EB) is a skin disorder. It causes fragile skin that develops blisters with little effort. This happens due to a mutation in keratin, which helps stabilize cells.
• Hereditary Spastic Paraplegia (HSP) and Charcot-Marie-Tooth Disease (CMT) are neurodegenerative diseases. They happen due to mutations in proteins like microtubules or neurofilaments in neurons. This leads to muscle weakness, sensory loss, and neuron degeneration.

These defects impact how neurons transport signals. This leads to muscle weakness, sensory loss, and progressive degeneration of motor neurons.

What are some interesting facts about the cytoskeleton?

The cytoskeleton is one of the most interesting and dynamic parts within the cell. Its functions provide support, aid movement, and allow communication within and between cells.

No one matches their complexity. The cytoskeleton is unique because it changes all the time. Most cell structures stay the same. The cell builds and breaks down the cytoskeleton in a continuous cycle.

This will enable the cell to change its shape in a short amount of time, move, and adapt to different conditions. When a cell divides, microtubules change shape.

They form the mitotic spindle. The spindle makes sure the two daughter cells get the same number of chromosomes.

The final feature of the cytoskeleton is intracellular transport. Motor proteins, like kinesin and dynein, act like highways. They transport cargo, such as vesicles and organelles, along microtubules or actin filaments.

This transport process is vital for keeping cells balanced by delivering materials to different cell parts.

In neurons, microtubules serve as tracks. They help transport important components to the synapse. This process can break down in neurodegenerative diseases, such as Alzheimer’s and Parkinson’s.

Notable too are the evolutionary implications of the cytoskeleton. Some scientists believe the cytoskeleton helped eukaryotic cells evolve from prokaryotic ancestors.

Prokaryotes had simple cytoskeletal structures from the start. These helped keep their shape and support cell division.

Eukaryotes later developed a more advanced cytoskeletal network. This change allowed them to grow into larger and more complex organisms.

Conclusion

The cytoskeleton is vital for many functions. It helps maintain cell shape and structure. It also plays a key role in movement, division, and transport.

The cytoskeleton not working can lead to serious problems in many diseases. These diseases affect various tissues and organ systems.

One of the most beautiful things about the cytoskeleton is its ability to adapt. It acts as a flexible framework that meets any new cell needs. So, the shape of the cell changes to fit new parts of the cytoplasm.

This helps with movement and cell division, allowing the cell to grow and thrive. The cytoskeleton helps move things inside the cell.

It carries needed substances along its pathways for the cell to use. These functions show how complex the cytoskeleton is.

They also show its role in the evolution of multicellular systems. The cytoskeleton and its related diseases are important for basic science and clinical medicine.

It sheds light on key cellular processes. This also points to possible treatment targets for various diseases.

The cytoskeleton is more than a simple structure. It is dynamic and serves many functions. It is essential for the health and operation of every cell.

References:

Microtubules, filaments | Learn Science at Scitable. (n.d.). https://www.nature.com/scitable/topicpage/microtubules-and-filaments-14052932/#:~:tex t=Microtubules%20and%20Filaments,is%20no%20single%20cytoskeletal%20componen t.

Libretexts. (2022, October 23). 14: The cytoskeleton. Biology LibreTexts. https://bio.libretexts.org/Courses/University_of_California_Davis/BIS_2A%3A_Introducto ry_Biology_(Easlon)/Readings/14%3A_The_Cytoskeleton

The Editors of Encyclopaedia Britannica. (1998, July 20). Cytoskeleton | Description, Structure, & Function. Encyclopedia Britannica. https://www.britannica.com/science/cytoskeleton

Cytoskeleton. (2023, October 30). Kenhub. https://www.kenhub.com/en/library/anatomy/cytoskeleton Khan Academy. (n.d.).

https://www.khanacademy.org/science/biology/structure-of-a-cell/tour-of-organelles/a/the-cytoskeleton

J. Keeling, P., & V. Koonin, E. (2014). Origin and Evolution of the Self-Organizing Cytoskeleton in the Network of Eukaryotic Organelles. PMC PubMed Central, 25183829. https://doi.org/10.1101/cshperspect.a016030

Microtubules, filaments | Learn Science at Scitable. (n.d.-b). https://www.nature.com/scitable/topicpage/microtubules-and-filaments-14052932/

Wickstead, B., & Gull, K. (2011). The evolution of the cytoskeleton. JCB Journal of Cell Biology, Rockefeller University Press. https://doi.org/10.1083/jcb.201102065

McMurray, C. T. (2000). Neurodegeneration: diseases of the cytoskeleton? Cell Death and Differentiation, 7(10), 861–865. https://doi.org/10.1038/sj.cdd.4400764

Ramaekers, F. C., & Bosman, F. T. (2004). The cytoskeleton and disease. The Journal of Pathology, 204(4), 351–354. https://doi.org/10.1002/path.1665

Gutiérrez‑Vargas, J., Castro‑Álvarez, J., Zapata‑Berruecos, J., Abdul‑Rahim, K., &

Arteaga‑Noriega, A. (2022). Neurodegeneration and convergent factors contributing to the deterioration of the cytoskeleton in Alzheimer’s disease, cerebral ischemia and multiple sclerosis (Review). Biomedical Reports, 16(4). https://doi.org/10.3892/br.2022.1510

Cytoskeletons shaking hands: Defects in cytoskeletal structures lead to various diseases. (2015, June 15). ScienceDaily. https://www.sciencedaily.com/releases/2015/06/150603083200.htm

Cartelli, D. (2021). Chapter 6 – Neuronal structure in aging: cytoskeleton in health and disease.

Assessments, Treatments and Modeling in Aging and Neurological Disease, 53–64. https://doi.org/10.1016/B978-0-12-818000-6.00006-8

Libretexts. (2023, August 31). 7.6: The cytoskeleton. Biology LibreTexts. https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(Kaiser)/Unit_4%3A_Eu karyotic_Microorganisms_and_Viruses/07%3A_The_Eukaryotic_Cell/7.6%3A_The_Cyto skeleton

The cytoskeleton, flagella and cilia, and the plasma membrane | Biology for Non-Majors i. (n.d.). https://courses.lumenlearning.com/wm-nmbiology1/chapter/the-cytoskeleton-flagella-and-cilia-and-the-plasma-membrane/

Cytoskeleton – the movers and shapers in the cell | British Society for Cell Biology. (n.d.). https://bscb.org/learning-resources/softcell-e-learning/cytoskeleton-the-movers-and-shap ers-in-the-cell/

Li, M., Peng, L., Wang, Z., Liu, L., Cao, M., Cui, J., Wu, F., & Yang, J. (2023). Roles of the cytoskeleton in human diseases. Molecular Biology Reports, 50(3), 2847–2856. https://doi.org/10.1007/s11033-022-08025-5

G. Stringham, E., Marcus-Gueret, N., Ramsay, L., & L. Schmidt, K. (2012). Chapter Eleven – Live cell imaging of the cytoskeleton. Methods in Enzymology, 505, 203–217. https://doi.org/10.1016/B978-0-12-388448-0.00019-X

M. Cooper, G. (2000). Chapter 11The Cytoskeleton and Cell Movement. The Cell: A Molecular Approach. 2nd Edition. https://www.ncbi.nlm.nih.gov/books/NBK9893/#:~:text=In%20addition%20to%20playing%20this,mitotic%20chromosomes)%20through%20the%20cytoplasm. Khan Academy. (n.d.-b).

https://www.khanacademy.org/test-prep/mcat/cells/eukaryotic-cells/a/organelles-article Dalton, L., & Young, R. (2024, January 1). The cytoskeleton. Pressbooks.

Written by Lawrence Barquilla

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

The mitochondria’s major role is to generate ATP or adenosine triphosphate. ATP is the cell’s primary energy source and is utilized for reactions. Cellular respiration produces ATP.

The mitochondrion (plural: mitochondria) is an organelle found in all eukaryotic cells. It is popularly known as the cell’s “powerhouse,” and its primary function is to produce energy for the body.

You will learn throughout this article about the powers of the cell’s powerhouse. You will also identify the key roles this organelle plays in the body’s normal physiology.

What is the major goal of cellular respiration?

Cellular respiration is the process of which the major goal is to produce ATP. This process occurs in the mitochondria of cells. Cellular respiration is an integral process. It is where the cells convert nutrients into usable energy in the form of ATP. Thus, the mitochondria sustain life.

The process of cellular respiration is a series of metabolic pathways. In these pathways, glucose and organic molecules break down to produce ATP. This occurs in three main stages as follows.

1. Glycolysis

This involves splitting one molecule of glucose into two molecules of pyruvate. It is the process of splitting a 6-carbon sugar into a 3-carbon sugar. This process generates a net gain of 2 ATP molecules. The method of substrate-level phosphorylation produces these 2 ATP molecules.

Alongside the ATP produced, electron carriers such as NADH molecules are also produced. These will be needed in the later stages of the process. Additionally, this stage occurs in the cytoplasm. Later on, the products will move into the mitochondria for further processing.

• Citric Acid Cycle

The pyruvate molecules from glycolysis now enter the mitochondria. Each of the 2 pyruvate molecules is converted into acetyl-CoA. The products then enter the citric acid cycle afterward. During this stage, ATP is not produced.

However, 2 GTP are produced, which function similarly to that of ATP. GTP stands for guanosine triphosphate. GTP is equal to 1 ATP per 1 GTP molecule produced.

Additionally, the products are electron carriers. These include NADH and FADH2, as well as carbon dioxide, which are waste products. These products will move into the next few steps of the process.

• Oxidative Phosphorylation

This is the final stage in the process of cellular respiration. It takes place in the inner mitochondrial membrane. The electron transport chain makes use of the electrons from the electron carriers.

From the previous steps, NADH and FADH2 serve as the electron carriers of the system. The electron carriers create a proton gradient. This proton gradient allows for the electron transport chain to operate. Additionally, this gradient is what drives the synthesis of ATP.

As electrons are transferred from the carriers, a proton gradient across the inner mitochondrial membrane is created. Once the electrons enter back into the mitochondrial matrix, they pass through the ATP synthase. As they pass through the enzyme, ATP is generated.

This step produces the most ATP among the stages. A total of 28 to 34 ATP molecules are produced.

Which cell in the human body does not have mitochondria?

The erythrocytes, commonly known as the red blood cells, are the only cells in the body that do not contain mitochondria. These erythrocytes not only lack the mitochondria but also lack other cell organelles, one of which is the nucleus.

Red blood cells function primarily to carry oxygen throughout the entire body. Thus, having the adaptation of losing the mitochondria allows for maximized oxygen transport.

By removing this specific organelle, the red blood cells can accommodate more hemoglobin. Once more hemoglobin is accommodated, more oxygen can be transported from the lungs to the tissues to the cells of the body.

Another point to look at is the shape and structure of red blood cells. They have a biconcave shape, which allows for an increased surface area for gas exchange. By removing the mitochondria and other organelles, the red blood cells are able to maximize the space.

Without the mitochondria, you may start to wonder how red blood cells produce energy for their own use. Well, they still have a reliable source of energy through the process of anaerobic respiration.

Anaerobic respiration involves metabolizing glucose through glycolysis. This is to generate ATP without the need for oxygen. Although possible, this is not as efficient as cellular or aerobic respiration. Anaerobic respiration is not as efficient in ATP generation.

Regardless, it enables red blood cells to attain energy. It is important to have an energy source as they carry and transport oxygen through the body.

Overall, having no mitochondria comes to be more beneficial for red blood cells. It is a crucial adaptation that improves their ability to carry oxygen efficiently. This interesting adaptation is what maintains the oxygen concentration at a healthy level.

Which organ contains the most mitochondria?

The heart is the organ that is most abundant in the amount of mitochondria. As the heart is in a continuous state of function, it needs significantly more energy than other organs of the body.

The heart holds the highest number of mitochondria. It amounts to about one-third or 30% of the total cardiac cell volume. The high mitochondrial density enables the heart to generate the needed amount of energy. This energy sustains the rhythmic contractions of the heart.

To help sustain the function of the heart, more ATP is needed. The heart beats about 100,000 times in one day. This activity requires a large amount of energy. As such, the need for more ATP is addressed by having more mitochondria in the cell itself.

The mitochondrial count is also high among other high-energy demanding organs. This includes your liver and skeletal muscles.

The liver is responsible for a lot of functions. It includes detoxification, protein synthesis, and regulation of biochemical reactions. Thus, hepatocytes need more ATP to enable the liver to function efficiently.

The skeletal muscles require a substantial amount of energy for contraction and movement. The more we move our bodies, the more energy is needed. The more active we are, the more mitochondria are required in order to produce more energy.

This all boils down to the fact that as the cells become more active, more energy is needed. In order to keep up with the increased need for energy, more mitochondria are required.

How many mitochondria does a human have?

By a general estimate, humans can have around 1000 mitochondria per cell. As such, the total mitochondria of a human being can be estimated to reach around 100 trillion mitochondria. The sum of all the mitochondria in each possible cell of the human body.

Mitochondrial density varies across different cell types. As you have learned earlier, some cells need more, while some don’t need the mitochondria at all.

By approximation, the diverse activities, functions, and processes a human being undergoes require a ton of energy supplied by the 100 trillion mitochondria everywhere.

What foods repair mitochondria?

Numerous scientists worldwide have recorded mitochondrial damage. As such, researchers discovered that this degradation is reversible. This can be done through food intake that supports and restores mitochondrial function.

1. Antioxidants

Antioxidants are good to combat the presence of free radicals. Free radicals are harmful to the cells and can damage the mitochondria even more. As such, antioxidants are a great way to combat the presence of risky free radicals.

Blueberries and other berries, in general, are packed with antioxidants. Pomegranate seeds have also been found to be high in antioxidants. They are also high in fiber, vitamin C, and potassium.

• B Vitamins

B vitamins work as co-enzymes. These help start up the mitochondrial engines to synthesize energy. These B vitamins are cofactors for many enzymes in the mitochondrial energy metabolism.

For optimal function of the mitochondria, adequate amounts of B vitamins and other vitamins must be observed. Beef is a great and complete source of B vitamins. Additionally, it contains healthy amounts of omega-3 fats.

• Sulfur

Sulfur compounds play a role in mitochondrial dynamics. They also contain antioxidant properties that reduce oxidative stress in the cell.

Sulfur can be sourced from broccoli and broccoli sprouts. They have far higher concentrations of sulfur in broccoli than among other vegetables.

• Fats

Fats in the mitochondria are used as part of a protective membrane. A diet comprised of high-quality fats and oils is essential to ensure a healthy mitochondrion.

Familiar healthy fat sources include olive oil, Butter, and Salmon. Olive oil is rich in phytonutrients that combat free radical damage efficiently. Butter, in healthy moderation, serves as a good source of fat-soluble vitamins.

Fatty fish such as salmon are high in essential omega-3 fatty acids. This helps support mitochondrial function as well as reduce inflammation.

• Magnesium

Magnesium is a mineral that performs numerous functions on a daily basis. The mitochondria depend on magnesium as it is a vital cofactor. Magnesium is involved in glycolysis, cell respiration, and transmembrane transport.

As such, magnesium is in avocados and spinach. Avocados are high in magnesium content as well as their monounsaturated fat. Spinach, along with most common green leafy vegetables, contains high and healthy amounts of magnesium.

It is essential to look at your diet and try to incorporate such examples into your meals. By doing so, you are able to support mitochondrial repair. You are also able to enhance your overall cellular energy turnover. This eventually leads to better health and lifestyle outcomes.

What happens if the mitochondria stop working?

Once the mitochondria stop working, a range of health issues collectively known as mitochondrial dysfunction can occur.

As you may have learned, the mitochondria serve an integral function in sustaining life. Once the mitochondria stop working, the cell will bear the consequences as follows.

1. Energy Deficiency

ATP production now happens at a much slower rate. It results in a significantly lesser turnover.

Aside from cellular respiration, there are also other means of producing ATP in the body. It can occur through beta-oxidation, ketosis, protein catabolism, and anaerobic metabolism. The problem here is that these are not as efficient as the mitochondria in ATP synthesis.

When the body functions continue, the lack of energy will cause a significant imbalance. An imbalance between the production and expenditure of ATP. Thus, an energy deficiency.

• Organ Defects and Dysfunction

Earlier, you have learned that some organs contain more mitochondria than others. This is because of their functions. Some require them to have more mitochondria and generate more energy.

As such, the inhibition of ATP production can lead to severe damage and complications to the heart, skeletal muscles, and kidneys, for instance. The effects can span a range of disorders that overall impair the body’s normal functioning.

• Metabolic Disorders

Metabolic disorders result from mitochondrial dysfunction, and these include mainly diabetes and obesity.

If the body continues to consume the daily food and nutrient intake, the inability to produce the same amount of energy causes an imbalance. This imbalance is between energy production and use leads to a defective metabolism.

Other diseases of a metabolic nature are type 2 diabetes, dyslipidemia, and cardiovascular diseases.

Overall, the mitochondria prove to be the cell’s powerhouse. Not just the cell but the entire body system’s powerhouse. All of the essential functions depend on ATP, and the mitochondria serve to produce as much ATP as needed. Without these important organelles, life would be put to a halt as we deal with its consequences. As such, keeping your body healthy lies at the forefront of ensuring that your organs, tissues organelles, and cells function efficiently.

References:

Bhatti, J. S., Bhatti, G. K., & Reddy, P. H. (2016). Mitochondrial dysfunction and oxidative stress in metabolic disorders — A step towards mitochondria based therapeutic strategies.

Biochimica et Biophysica Acta (BBA) – Molecular Basis of Disease, 1863(5), 1066–1077. https://doi.org/10.1016/j.bbadis.2016.11.010

Brand, M. D., Orr, A. L., I.V. Perevoshchikova, & Quinlan, C. L. (2013). The role of mitochondrial function and cellular bioenergetics in aging and disease. British Journal of Dermatology, 169, 1–8. https://doi.org/10.1111/bjd.12208

Cox, A. (2019). Top 9 Foods You Need to Boost Your Mitochondria – Institute for Restorative Health. Institute for Restorative Health. https://instituteforrestorativehealth.com/2019/07/09/top-9-foods-you-need-to-boost-your- mitochondria/ health.com/2019/07/09/top-9-foods-you-need-to-boost-your-mitochondria/

Hashiguchi, K., & Qiu-Mei Zhang-Akiyama. (2009). Establishment of Human Cell Lines Lacking Mitochondrial DNA. Methods in Molecular Biology, 383–391. https://doi.org/10.1007/978-1-59745-521-3_23

Li, A., Shami, G. J., Griffiths, L., Lal, S., Irving, H., & Braet, F. (2023). Giant mitochondria in cardiomyocytes: cellular architecture in health and disease. Basic Research in Cardiology, 118(1). https://doi.org/10.1007/s00395-023-01011-3

Mouna Habbane, Montoya, J., Taha Rhouda, Yousra Sbaoui, Driss Radallah, & Emperador, S. (2021). Human Mitochondrial DNA: Particularities and Diseases. Biomedicines, 9(10), 1364–1364. https://doi.org/10.3390/biomedicines9101364

Rogers, K. (2009, January 19). Mitochondrion | Definition, Function, Structure, & Facts.

Encyclopedia Britannica. https://www.britannica.com/science/mitochondrion

Zhang, Z., Cheng, J., Xu, F., Chen, Y., Du, J., Yuan, M., Zhu, F., Xu, X., & Yuan, S. (2011). Red blood cell extrudes the nucleus and mitochondria against oxidative stress. IUBMB Life, 63(7), 560–565. https://doi.org/10.1002/iub.490

Written by: Therese C. Oyales

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

A histopathologist diagnoses diseases after careful examination of a tissue sample. They track the disease’s progression by looking for abnormal changes in the cells. Cancer cells, infections, and inflammations are the kinds of abnormalities histopathologists check for.

Histopathologists do not work alone. They work in a multidisciplinary team. This team documents, processes, or examines the patient’s samples (biopsy). They also meet with other physicians to discuss the findings. Some healthcare professionals they work with include:

• Laboratory staff
• Nurses
• Molecular scientists
• Mortuary staff
• Surgeons
• Oncologists
• Radiologists
• Forensic medicine scientist

These healthcare workers discuss each patient’s condition and create a treatment plan that suits their individual needs. Once treatment has started, they will monitor its effectiveness. They will continue the medication or therapy if the histopathologist notices signs of healing.

The field of histopathology is not limited to samples from living people. A forensic histopathologist determines the cause of death of individuals at crime scenes. Generally, they do not perform autopsies. They do microscopic analyses on tissues from internal organs.

Tools of the trade

Did you know that the microscope is the most essential tool in a histopathology laboratory? It allows the histopathologist to view organisms that are too small to see with the naked eye. It reveals the cells’ detailed structures and the presence of abnormalities.

Some equipment used for tissue preparation are:

• Microtome

A microtome slices the block of embedded tissue into very thin sections. It is a precise and accurate instrument that creates “ribbons” for easy sequencing of the sections. Different microtomes are used for paraffin, plastic, and frozen sections due to the material’s toughness.

• Paraffin wax bath

The histopathologist manipulates the sections using a paraffin wax bath to arrange them into the desired orientation and location. They transfer the sections into glass slides using the hot distilled water from the bath.

• Automatic Tissue Processor

An automatic tissue processor prepares tissues for the histopathologist. It can fix, dehydrate, clear, and infiltrate the specimen.

• Embedding Cassettes

Histopathologists use embedding cassettes to secure the tissue specimens for storage, processing, and embedding.

Who is the father of tissue study?

Marie-François Xavier Bichat is regarded as the father of tissue study. He was a French anatomist, pathologist, and physiologist whose contributions led to the establishment of the scientific study of tissues.

Bichat was born on November 14, 1771, in Bresse, France. His family supported his interest in science and medicine. His father, Jean Baptiste Bichat, was a physician at Montpellier and was a great inspiration to the young boy.

He started his medical journey at Lyon, where Marc-Antoine Petit, a chief surgeon at the Hôtel Dieu, became his mentor. In 1793, he studied under a surgeon and anatomist called Pierre-Joseph Desault. After his teacher passed, he continued doing research and publishing books on his own.

Contributions

• Pioneer of histology. Bichat was the first to study tissues. He proposed that organs are made up of groups of tissues that share similar structure and function. He discovered the organizational level between organs and cells, and these are tissues.

• Correlation between structure and function. Bichat established that the structure of cells and tissues relates to their function. Their arrangement and shape are tied to their specific roles in the body.

• Classification of tissues. Bichat distinguished 21 kinds of tissues based on their specific characteristics. He analyzed the different combinations and roles of each tissue kind.

Publications

• Traité des membranes (Treatise on Membranes)
• Recherches physiologiques sur la vie et la mort (Physiological Research on Life and Death)
• Anatomie Générale (General Anatomy) Volumes I & II

Who is the father of pathology?

Rudolf Virchow, a physician, pathologist, and politician, made profound contributions to cellular pathology. Hence, he is now known as the “father of pathology.” His works helped us better understand the nature of diseases. And, how they can be accurately diagnosed on a cellular level.

Virchow was born on October 13, 1821, in Schivelbein, Prussia. He studied medicine in Berlin and graduated as a medical doctor in 1843. He published a journal with his friend, Benino Reinhardt, which was later renamed “Virchow’s Archives”. To this day, it continues to publish cutting-edge research articles on human pathology.

Virchow recognized the importance of the microscope for its ability to view the cell’s activities. He made advancements in science and human anatomy using this tool. One of these was discovering the cell theory’s last principle in 1850 when he observed the process of cell division.

Contributions

• All cells come from preexisting cells. Virchow added the final principle of the cell theory. It supports biogenesis, which states that living organisms arise from other living organisms. He emphasized that cells are formed by the division of other cells, either through mitosis or meiosis.

• Cellular pathology. According to Virchow, diseases arose in individual cells rather than tissues or organs. He argued that abnormalities and trauma within the cell caused it to manifest in tissues and organs.

• Embolism connection to metastatic inflammation. Virchow coined the terms “thrombus” and “embolism”. An embolism is the blockage of a blood vessel by an embolus (e.g. blood clot). Metastatic inflammation refers to inflammation caused by the spread of cancer cells.

He speculated that embolism was the most common cause of metastatic inflammation of the lungs. He was able to confirm this by comparing several cases. He also observed that thrombosis was present in these blood vessels where the cancer cells were.

• Medical Education in Germany. Virchow was a teacher at the University of Würzburg and the University of Berlin. His expansive knowledge of medicine, coupled with a passion for teaching, produced many brilliant minds. Some even became famous scientists.

Publications

• Archiv für pathologische Anatomie und Physiologie, und für klinische Medizin (Archives for Pathological Anatomy and Physiology, and for Clinical Medicine) (now Virchow’s Archives)
• Die Cellularpathologie in ihrer Begründung auf physiologische und pathologische Gewebelehre (Cellular Pathology as Based upon Physiological and Pathological Histology)
• Handbuch der speziellen Pathologie und Therapie (Handbook of Special Pathology and Therapeutics)

Who are the scientists who contributed to histology?

Aside from Bichat, other notable scientists who made contributions to the development of histology are Schwann, Schleiden, Cajal, and Ehrlich.

• Schwann

Theodor Schwann was a German physiologist known for his contributions to developing the cell theory. He and Matthias Schleiden proposed that cells are the basic structural unit of life. Specifically, he stated that cells are the fundamental unit of animal structure.

Schwann also identified the role of the myelin sheath covering the axons in the peripheral nervous system (PNS). These were named Schwann cells. They are responsible for insulating axons to facilitate faster transmission of electrical impulses.

• Schlieden

Matthias Jakob Schleiden is a German botanist who proposed that cells are the fundamental unit of plant structure. He and Schwann collaborated to find a unit of organisms similar to both plants and animals.

Schwann also did research on cytogenesis. He recognized the importance of the nucleus in cell formation. He described the cell division process and included the activities of the nucleus. However, a more detailed version of cell division was developed at a later time.

• Cajal

Santiago Ramón y Cajal was a Spanish histologist and neuroscientist. He is credited for establishing the neuron as the fundamental unit of the nervous system. It revolutionized our understanding of the brain and the nervous system.

The properties of nervous tissues and other components of the nervous system are distinct from the rest of the body. Cajal developed the gold stain so you could clearly visualize the neurons and differentiate them from other cells. It is also useful for diagnosing brain tumors.

• Ehrlich

Paul Ehrlich is a German scientist known for developing dyeing and staining techniques. These allowed you to study various cells that could be better viewed with specific dyes (e.g. erythrocytes and leukocytes). It was also significant in the diagnosis of anemia, leukemia, and other blood disorders.

The principle of chemical affinity should be considered when staining. Ehrlich discovered that histological dyes could be acidic, basic, or neutral. They should be paired according to the pH of the tissue or cell.

Who studies histology?

Before knowing who studies histology, you must first know the meaning of histology. Histology is the study of tissues. It involves examining the structure of tissues in relation to their functions. The findings on human tissues enhanced our understanding of diseases.

Professions related to medicine, biology, healthcare, and research study histology. In medicine, histologists and histopathologists use tissue knowledge in the patient’s treatment. They assist other health professionals by analyzing tissue samples under the microscope.

Medical students also benefit from histology. It was made into a prerequisite subject designed to lay a foundation for more advanced medical concepts. A solid understanding of histology will help students grasp the intricate details of human anatomy.

Other healthcare professionals (nurses and physical therapists) study histology to treat tissue- related injuries. They need to be informed about how first-aid procedures and therapy can affect wounds, lacerations, or bruises. For example, discoloration can be a sign of tissue trauma.

Histology can also answer questions on how tissues are affected by drugs and medicine. Pharmacologists and pharmacists must learn histology to ensure that any medicine is safe to consume. They must know the right dosage so as not to cause harm to patients.

Biomedical researchers also study histology to expand the existing literature in this field. New applications can be discovered through past findings by scientists. Human histology can also be compared to plant histology and the histology of other animals.

What is the purpose of histologic examination?

Histologic examinations are when tissue samples are examined under a microscope. It is performed to check for abnormalities in cells or tissues. A histologic examination is carried out by a histopathologist or a pathologist.

These physicians do a histological examination to diagnose diseases. They assess whether a tumor is malignant (cancerous) or benign. They also check for infections, inflammations, and autoimmune diseases. It confirms the suspicions of physicians from the patient’s physical examination.

A histologic examination is also useful for understanding tissue function and structure. Through the years, observation of tissue specimens has led to the accumulation of valuable information. For example, people can now differentiate a healthy tissue from a diseased one.

Types of histological examination

There are two methods for performing histological examination: standard and urgent. They differ based on the purpose and duration. You use standard for routine, non-emergency procedures. It can be for annual follow-up check-ups or benign tumors.

In a standard histological examination, tissue preparation lasts for several hours or days. The process of tissue preparation, which involves fixing up to staining, will take its usual duration.

When the patient is going to have emergency surgery, you request an urgent histological examination. It is when the state of the tissue or cells must be found within the hour. It provides crucial information to guide medical decisions, which can be life or death for the patient.

What is the aim of histology?

The primary aim of histology is to determine how tissues are organized across various structural levels. This allows us to comprehend how different tissues maintain a healthy body or heal or regenerate from a disease.

Histology also aims to study how tissue and cell structure correlate to their function. It is essential to learn how they interact. Further research can be done on this principle. It offers new opportunities for improving diagnostics to address emerging health issues.

It was mentioned previously that histology is useful for diagnosing diseases. More diseases are emerging. Histology remains a crucial tool that is helpful for identifying the causative agents of such diseases.

Conclusion

Histology changed the course of medicine and healthcare. It has become an essential tool in saving and improving the lives of people. It is useful for diagnosing diseases, understanding the structure and function of tissues, and tracking disease progression.

Many scientists, such as Bichat and Virchow, contributed to the field of histology and pathology. Their discoveries and developments led to new theories that were later proven by other scientists. Using their findings, today’s scientists further our understanding of the human body.

References:

Britannica, The Editors of Encyclopaedia. (2024, July 18). Marie-François-Xavier Bichat. Britannica.

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Britannica, The Editors of Encyclopaedia. (2024, October 13). Santiago Ramón y Cajal. Britannica.

Retrieved from https://www.britannica.com/biography/Santiago-Ramon-y-Cajal.

Britannica, The Editors of Encyclopaedia. (2025, January 7). Theodor Schwann. Britannica.

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Written by Kyle Peter Josh Bernaldez Deluvio

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

Try to picture an airport with a control tower. Through observation, you can see several airplanes. You can see them arriving and departing in an organized and systematic manner. Why? This is because of the airport’s control tower. It navigates planes by directing them when to take off and land. Now, the airport’s control tower functions in a similar manner to the cell’s nucleus. The cell’s nucleus coordinates several activities of the cell. This includes gene expression, growth, and reproduction. Like the airport, the cell will be in total disarray without the nucleus. This will result in consequences to the total function of the human body.

Hence, the nucleus is an essential structure in the cell. It holds the blueprint of life, the instructions for growth, and the codes for development. The nucleus necessitates the progression of human life.

Structure and Function

The nucleus is a spherical structure situated at the center of the cell. Although its shape is often spherical, it usually conforms to the shape of the cell. Furthermore, it serves as a repository for the cell’s hereditary material. The genetic material, deoxyribonucleic acid (DNA), includes instructions necessary for the body’s development.

Apart from housing genetic information, the nucleus also has the following functions:

• Serves as the cell’s control center.
• Serves as the site for DNA replication, transcription, and RNA processing.
• Regulates protein and enzyme synthesis
• Controls heredity
• Controls cell growth and cell division
• Production of ribosomes

To better understand the functions listed, exploring the parts of the nucleus is vital.

Parts of the Nucleus

A double-membrane structure, called the nuclear envelope, encloses the nucleus. Tiny channels are also present in the membrane, called nuclear pores. Furthermore, the nucleolus is found deeper into the nucleus.

The substance that resembles the cytoplasm and fills the nucleus is called the nucleoplasm. Moreover, found beneath the inner nuclear membrane is called the nuclear lamina.

(1)  Nuclear Envelope.

• It is a double-membrane structure, each made out of a phospholipid bilayer. It serves as the barrier of the nucleus that regulates what passes through it. It encloses a jelly-like fluid called the nucleoplasm. In it, suspended are other nuclear elements are suspended in it.
• The outer membrane attaches to the rough endoplasmic reticulum. Like the rough endoplasmic reticulum, the nuclear envelope has ribosomes attached to it.
• The inner membrane is where nucleus-unique proteins attach.

(2)  Nuclear Pores.

• It controls the movement of macromolecules, which is called nuclear transport.

(3)  Nucleolus

• These condensed regions of chromosomes are where ribosomal RNA is being synthesized. Such ribosomal RNA are essential components of ribosomes.

• This serves as the site for the assemblage of ribosomes and sites for protein synthesis.

(4)  Nucleoplasm

• It is the same with the cytoplasm. It is semi-liquid, and it fills the nucleus of the cell.
• It surrounds the chromosomes and nucleoli inside the nucleus.
• The nucleoplasm of the nucleus also has elements dissolved in it. These elements are proteins and enzymes.

(5)  Nuclear Lamina

• It is made up of V intermediate filament proteins called lamin proteins
• It provides structural and mechanical support to the nucleus of the cell.It helps in the proper positioning of the nucleus in the cell.
• It is significant in ensuring the proper organization of chromatin inside the nucleus.

What is the origin of the nucleus?

There are several approaches to understanding the origin of the nucleus. Two of the accepted approaches include: the invagination theory and the endosymbiont theory.

(1)  The Invagination Theory of the Nucleus

This theory asserts that the nucleus of the cell originated from the invagination. It proposes that the invagination occurred in a very ancient anaerobic archaeon.

It demonstrates that a segment of the cell membrane folded inwards (invaginated). This enclosed the genetic material attached to that segment of the cell membrane.

In succeeding generations, the cell formed a two-layered envelope that surrounded the DNA. It is a presumption that the envelope, later on, pinched off from the plasma membrane.

From there, the nuclear compartment of the cell existed. Several channels, called nuclear pores, penetrated the compartment. This enabled communication with the cytosol.

This compartmentalization serves as an advantage for the nucleus. It provides better organization and protection for the genetic material inside the nucleus.

Furthermore, other membranes of the invaginated membrane may have served other purposes. For instance, it may have formed the endoplasmic reticulum. This explains the continuity of the space. The space between the layers of the nuclear envelope and the endoplasmic reticulum.

(2)  The endosymbiont theory of the nucleus

This theory suggests that the cell’s nucleus originated from a prokaryotic cell. Later on, an amoeboid cell engulfed the prokaryotic cell. After engulfment, the amoeboid cell made the prokaryotic cell its own nucleus.

In essence, the theory asserts that the nucleus is an integrated structure. According to this theory, the nucleus was a former independent structure. After the bacteria-like organism was inside another cell, its functions ceased. Meanwhile, it contributed its genetic material to the host cell that engulfed it.

Mereschkowsky (2010) proposed this theory of the origin of the nucleus.

Why is the nucleus the most important part of the cell?

The nucleus is the most important part of the cell because of several reasons. The reasons all revolve around one common understanding — the nucleus regulates cellular activities.

The nucleus contains genetic material called DNA. DNA is an essential part of human development as it holds instructions. The instructions that it holds are essential for the synthesis of proteins. Also, they are important for the synthesis of proteins.

The nucleus regulates what genes to silence and express. In this sense, the nucleus is responsible for several processes and mechanisms. This includes metabolism, growth and development, repair and replication,

The nucleus ensures proper cell division and replication. The nucleus ensures that the daughter cells contain an identical set of chromosomes. This is vital for the survival and growth of the new cells.

Ribosomal production also happens inside the nucleus. Serving as the site for ribosomal production, the nucleus necessitates protein synthesis.

What is the main function of the nucleolus?

The nucleolus is a large ribosome-producing factory. It is the nuclear compartment where transcription of the ribosomal RNAs occurs. Furthermore, it is also where the assemblage of the ribosomal subunits occurs.

In essence, the nucleolus has RNA products. These products are then combined with proteins to form ribosomes. Moreover, the ribosomes are exported to the cytosol. The cytosol is the site where translation will take place.

What happens if the nucleus of a cell is damaged?

Once damage impacts the nucleus of the cell, several possibilities arise. These depend on the severity of the damage, cellular context, and genetic factors.

If the damage is less severe, the nucleus has mechanisms in store. These include self-sealing and repair mechanisms. In particular, these mechanisms are responsible for mending the damaged nuclear membrane.

The following are among the restoring abilities of the cell:

• The self-sealing capabilities of the lipid bilayer covering the nucleus. When there is a tear in the nuclear membrane, exposure of the hydrophobic centers occurs. The hydrophobic parts attract each other. This allows them to connect and immediately heal.
• Cellular context of the nucleus. When the cell is undergoing mitosis or cell division, the cell can repair itself.
• The Role of Nuclear Pore Complexes (NPCs). These complexes are large protein assemblies. They regulate the shuttle system of molecules inside and out of the nucleus. With regards to repair, they help seal and stabilize the nuclear envelope.

Yet, if the damage is, to an extent, severe, the nucleus fails to repair itself. This leads to its eventual death. This usually happens when there is severe mechanical stress. Furthermore, it also occurs when there is cellular aging or senescence.

If the nucleus cannot sustain the damage, it will have immediate and long-term effects. These include the following:

• Nuclear envelope rupture. It is a fact that the nuclear envelope maintains the integrity of the nucleus. When the envelope ruptures, cytoplasmic and nuclear components interact. This, then, disrupts cellular processes. In particular, this infringes on the transcription and translation processes.
• DNA damage. The exposure of the cell’s DNA to the cytoplasmic membranes leads to consequences. For instance, it leads to fragmentation or the loss of genetic material. Furthermore, this leads to cellular stress response and apoptosis (cell death).
• Genomic instability. Nuclear damage results in several issues related to the cell’s genetic material. It is often related to mutations and an increased risk of cancer.
• Increased risk of disease. Diseases, such as cancers, often arise. This is when compromise happens to nuclear function and DNA damage occurs.

Can a cell survive without a nucleus?

The cell type dictates whether the cell survives with or without a nucleus. If the cell type is a prokaryotic cell, it tends to function well. This is because the genetic material of the cell is not located inside the nucleus. Instead, the cell’s instructions tend to situate in a region called the nucleoid.

In this sense, bacteria and archaea — considered prokaryotes — survive without a nucleus. Additionally, other cell types, such as erythrocytes and platelets, also thrive.

Yet, if the cell is a eukaryotic cell, the cell will not survive. This is because an integral aspect of the cell is its nucleus. Serving as the control center of the cell, it regulates cell function. It controls cell activity and ushers the gene expression.

Without the nucleus, the cell will die. Examples of these cells include nerve cells, muscle cells, and epithelial cells. These are essential for the proper functioning of the human body.

Do all cells have a nucleus?

Not all cells have a nucleus. For instance, prokaryotic cells do not have one. Unlike the eukaryotic cell, it does not have a nucleus to enclose its genetic material.

More information on prokaryotic cells

Prokaryotic cells or prokaryotes are single-celled organisms. They are often spherical, rod-shaped, or corkscrew-shaped. They are small, ranging up to a few micrometers long.

Despite the absence of the nucleus, the prokaryotes still have their DNA. Their DNA, or genetic material, is arranged in an irregular-shaped region called the nucleoid. This region is essential in storing the prokaryotic cell’s genetic material.

Prokaryotes, like eukaryotes, have a cell membrane. Instead of the nucleus, the cell membrane is present. The cell membrane is in control of enclosing the cell’s genetic material.

Examples of organisms that lack a nucleus are bacteria, archaea, and blue-green algae. In particular, they include Escherichia coli, Cyanobacteria, Streptococcus, and many more.

Other cells that do not have a nucleus

Mature red blood cells (erythrocytes) also do not have a nucleus. These specialized cells are accountable for the transport of oxygen across the body. The lack of a nucleus is an important characteristic of red blood cells. In fact, it contributes to its biconcave shape and flexibility. Moreover, it provides more space for hemoglobin, the protein that carries oxygen.

Hence, not all cells have a nucleus. But all cells have DNA.

Conclusion

Comparable to a plane’s command center, the cell nucleus coordinates all of the vital processes necessary for efficient and seamless operation. The nucleus contains deoxyribonucleic acid (DNA), the genetic material that functions as the coordinator for all cellular functions, much like the command center of the airport that directs the arrival and departure of numerous aircraft.

Similar to how the nucleus uses messenger RNA (ribonucleic acid) to coordinate protein synthesis, communication systems in the plane transmit commands to various components.

Just as a cell would stop functioning without the systematic direction of its nucleus, the plane would lose direction and coherence without this crucial command center. Ultimately, the nucleus is essential in regulating cellular processes and functions, all vital to life.

Ultimately, the nucleus is responsible for ensuring the complex machinery of the cell follows a systematic, orderly, and organized process. As part of the bigger picture, it ensures that the “flight” of life proceeds without significant barriers or consequences. Without the nucleus, we will undoubtedly be in complete disarray — especially with where we are headed.

References:

Al-Muhtaseb, T. (2021). Building a Tensegrity-Based Computational Model to Understand Endothelial Alignment Under Flow. https://doi.org/10.7912/C2/102

Baxter,            R.            (2020,            October            29).            Cell            nucleus.           Kenhub. https://www.kenhub.com/en/library/anatomy/cell-nucleus

Cooper, G. M. (2000). The Nucleus. The Cell: A Molecular Approach. 2nd Edition, 2(Chapter 8). https://www.ncbi.nlm.nih.gov/books/NBK9845/

Dean, L. (2005). Blood Groups and Red Cell Antigens. National Library of Medicine; National Center for Biotechnology Information (US). https://www.ncbi.nlm.nih.gov/books/NBK2263/

Gauthier, B. R., & Comaills, V. (2021). Nuclear Envelope Integrity in Health and Disease: Consequences on Genome Instability and Inflammation. International Journal of Molecular Sciences, 22(14), 7281. https://doi.org/10.3390/ijms22147281

Isermann, P., & Lammerding, J. (2017). Consequences of a tight squeeze: Nuclear envelope rupture and repair. Nucleus, 8(3), 268–274. https://doi.org/10.1080/19491034.2017.1292191

Lodé, T. (2012). For Quite a Few Chromosomes More: The Origin of Eukaryotes…. Journal of Molecular Biology, 423(2), 135–142. https://doi.org/10.1016/j.jmb.2012.07.005

Maciejowski, J., & Hatch, E. M. (2020). Nuclear Membrane Rupture and Its Consequences. Annual Review of Cell and Developmental Biology, 36(1), 85–114. https://doi.org/10.1146/annurev-cellbio-020520-120627

Marieb, E. N., & Keller, S. M. (2022). Essentials of Human Anatomy & Physiology (13th ed.). Pearson. Martin, W. F., Garg, S., & Zimorski, V. (2015). Endosymbiotic theories for eukaryote origin.

Philosophical Transactions of the Royal Society B: Biological Sciences, 370(1678), 20140330. https://doi.org/10.1098/rstb.2014.0330

Tortora, G. J., Funke, B. R., & Case, C. L. (2019). Microbiology: An Introduction (13th ed.). Pearson.

Written by Yara Patrice Formento

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

Angina pectoris, or angina, is chest pain caused by reduced blood flow to the heart. It is not a disease, but it is a symptom of underlying cardiovascular conditions such as coronary artery disease (CAD).

Angina manifests when the myocardium does not receive enough oxygen-rich blood. Angina occurs either when the heart is pumping hard or at rest, depending on the severity of the underlying factor.

Mayo Clinic describes angina as squeezing, pressure, tightness, and burning in the chest as if something heavy is pressing against the chest. It may also feel like indigestion or heartburn.

The discomfort can radiate to the shoulders, arms, neck, jaw, and back, similar to a heart attack. However, angina subsides with rest or specific medication, unlike a heart attack.

According to Hermiz and Sedhai (2023), chronic stable angina affects approximately 30,000 to 40,000 people per million people in Western countries. It is important to note that not all chest pain is angina and that it manifests differently for everyone.

Generally, when the myocardium lacks oxygen due to inadequate blood supply, this results in angina pectoris.

When the heart beats rapidly, the myocardium may receive inadequate oxygen-rich blood supply because relaxation periods (when the blood can flow to the heart tissue) are short-ended.

It can also be due to the narrowing and blocking of coronary arteries by atherosclerotic or lipid plaque. This condition is called coronary artery disease (CAD). As a consequence, a rupture or blood clot may occur.

Additionally, when the heart muscle does not receive enough oxygen, it causes ischemia.

1. At the cellular level, ischemia causes an increase in anaerobic glycolysis. Anaerobic glycolysis refers to the production of energy in the cells without oxygen. The end product of anaerobic glycolysis is two pyruvate molecules, which are then converted to lactic acid (lactate) for glycolysis to continue.
2. Anaerobic glycolysis increases the levels of hydrogen (pH), potassium, and lactate in the affected area of the myocardium.
3. The hydrogen ions compete with calcium ions, causing hypokinesia (reduced movement) or akinesia (no movement) in the affected area.
4. The affected cells also release adenosine and bradykinin. These chemicals stimulate nearby pain receptors (nociceptors).
5. The build-up of carbon dioxide and a drop in the pH due to anaerobic metabolism contributes to the sensation of pain.
6. Next, the pain signals travel along sympathetic nerve fibers and the vagus nerve, which send these signals to the brain, resulting in the perception of chest pain.
7. The activated sympathetic nervous system causes secondary symptoms such as sweating, anxiety, increased heart rate, and distress.

One should not ignore angina. The oxygen-deprived heart cells may die when prolonged, forming an infarct area. This results in myocardial infarction, more commonly known as heart attack.

What can trigger angina?

When a person is at risk for heart disease or coronary artery disease, he or she is also at risk for angina. Risk factors for people to develop coronary artery disease (CAD) include:

• Smoking and tobacco use
• High blood pressure
• Increasing age
• Diabetes
• High cholesterol levels
• Obesity
• Type “A” or Alpha personalities (refers to individuals who are consistently working and experience higher stress levels than most individuals)
• Emotional stress
• Drug abuse
• Sedentary lifestyle
• Genetics
• Medicines
• Cold temperatures
• Other health conditions such as chronic kidney disease, peripheral artery disease, metabolic syndrome, or stroke history

Most of these risk factors can be modified by changing diet and sedentary habits and controlled through medication. However, some risk factors are uncontrollable, such as genetics, age, and gender.

For instance, according to Tortora and Derrickson (2009), adult males are more likely than adult females to develop CAD. However, after age 70, all the risk factors are roughly equal. Smoking is the leading risk factor in all CAD-associated diseases, increasing the risk of morbidity and mortality.

What are the symptoms of an angina attack?

According to the Mayo Clinic, symptoms of angina include:

• Chest pain or pressure
• Intense sweating
• Difficulty catching breath
• Pain in the arm, neck, jaw, and shoulder
• Nausea
• Fatigue
• Feeling of gas or indigestion
• Fluctuating chest pain

Chest pain occurring with angina can make executing simple activities uncomfortable, but the most dangerous complication is a heart attack. The warning symptoms of a heart attack include:

• Pressure, fullness, or a squeezing pain in the chest that lasts for more than a few minutes
• Pain extending beyond the chest to the shoulder, arm, or back, and even to the teeth and jaw
• Fainting
• Threatening sense of doom
• Nausea and vomiting
• Continued pain in the upper belly area
• Shortness of breath
• Sweating

A person experiencing these symptoms must seek immediate medical help from a healthcare professional. The healthcare professional will perform a physical exam and ask about symptoms and risk factors, such as the family history of heart disease and other health conditions.

Where is angina pain located?

Angina pain primarily occurs in the chest area, yet it may also radiate to the neck, shoulders, and arms, especially the left arm, back, and jaw.

How long does angina pain last?

The duration of angina pain varies depending on its type. Angina due to the blockage of coronary arteries is classified into three categories:

1. Stable angina is the most common form of angina during exertion or activity. It disappears with rest or by taking medicine for angina. It is also predictable, similar to previous episodes of chest pain, and lasts a short time, approximately five minutes or less.
2. Unstable angina is unpredictable and occurs at rest. It is typically severe and lasts longer than stable angina, approximately for more than 20 minutes. Prolonged unstable angina can lead to myocardial infarction or heart attack due to the lack of oxygen in the heart. Generally, it is dangerous and requires emergency treatment.
3. Variant angina, or Prinzmetal angina, is caused by spasms in the heart’s arteries rather than coronary artery disease (CAD). The spasm temporarily reduces blood flow, with severe chest pain as the main symptom. It often occurs in cycles, from rest and overnight. It can be relieved by taking angina medicine.

Moreover, suppose a healthcare professional thinks that a patient has unstable angina or a severe underlying factor. In that case, tests such as an electrocardiogram, stress test, blood tests, chest x- rays, coronary angiography, cardiac catheterization, and computer tomography angiography may be done.

• Electrocardiogram. It records the heart’s electrical activity and shows whether a person is at an increased risk for heart attack.
• Stress test. A person walks on a treadmill to elevate their heart rate while receiving an electrocardiogram. The test reveals whether the heart gets enough oxygen-rich blood when physically exerted.
• Blood test The presence of substances in the blood, such as troponin, can indicate whether a person is at an increased risk for a heart attack. High levels of troponin indicate whether a person is having or has had a heart attack.
• Chest x-ray.
• CT scan. It assesses the calcium build-up or blood flow in the coronary arteries.
• Holter monitor. A device is worn for 24 hours or longer to record and look for abnormalities in the heart rhythm.
• Coronary angiography. A procedure wherein contrast dye is injected into the bloodstream to reveal, through X-ray images, possible blockages within coronary arteries.
• Cardiac catheterization. A general procedure wherein a doctor inserts a catheter into a large blood vessel. It can be used for angiography, angioplasty (when the catheter is used to clear a blocked artery and valvuloplasty (when the catheter is used to widen a narrow heart valve).

What is the fastest way to stop angina?

The fastest way to stop an angina attack is through medication, specifically nitroglycerin. Nitroglycerin is a nitrate that causes the coronary arteries to widen, increasing blood flow.

Nitroglycerin is placed under the tongue when a person first feels discomfort and pain and should relieve angina within 5 minutes. Long-acting nitrates, diagnosed by physicians for patients to take daily, help prevent angina attacks.

Other medications to stop angina include:

• Beta blockers. They decrease the heart rate, reduce the risk of abnormal heart rhythms, and decrease blood pressure.
• Calcium channel blockers. An alternative to beta blockers for people with asthma or chronic obstructive lung disease, heart block and related conduction system abnormalities, and peripheral artery disease. They lower blood pressure and widen coronary arteries.
• Aspirin. It prevents the formation of blood clots in diseased blood vessels, which are the leading cause of heart attack and stroke.
• Statins. An umbrella term for drugs used to lower cholesterol. They also reduce inflammation in blood vessels and prevent plaque from breaking open.
• ACE inhibitors. They help relax blood vessels throughout the body.
• Ranolazine. It reduces the amount of oxygen the heart needs to do its work.

Moreover, when medical therapy does not relieve angina and if it suddenly progresses, more invasive treatments may be required.

An angioplasty is a surgical procedure wherein the doctor inserts a catheter into an artery in the groin or arm and then carefully maneuvers it into the blocked artery. Next, the doctor inflates a balloon at the artery’s tip, flattening the plaque that is blocking the artery.

• Sometimes, the balloon also expands a wire mesh stent to hold the artery open and leaves it in place.
• This process can take 30 minutes to several hours. A patient usually stays in the hospital at least overnight. The healthcare team tells them when they can return to their daily activities.
• Sometimes, the blockage returns after an angioplasty. Using a stent coated with medicine can help prevent this.

If unstable angina or stable angina affects some of the leading heart arteries and does not improve with stenting and other treatments, heart bypass surgery may be needed.

Coronary Artery Bypass Grafting is a surgical procedure wherein a surgeon uses a blood vessel from another part of the body to make a new channel. It diverts blood around the blocked coronary artery.

However, prevention is better than cure. Aside from medication and medical procedures, the best way to treat angina is to change one’s lifestyle ultimately. This includes but is not limited to:

• Stopping tobacco use and smoking. Smoking contributes to atherosclerosis, or the build- up of plaque in the arteries, which reduces blood and oxygen supply throughout the body. If a person needs help quitting, he/she should consult his/her healthcare team about therapies that can help.
• Losing weight if needed. Obesity accelerates early atherosclerotic changes, including the development of fatty streaks. It is associated with blood pressure, dyslipidemia, and hyperglycemia.
• Lowering blood sugar, blood pressure, and cholesterol levels. It concerns having a healthy diet, exercising regularly, managing emotional health, and quitting smoking.
• Adjusting daily activities. If a certain kind of activity can cause angina, try performing the activity more slowly. Also, since the heart is more stressed in the mornings and after meals, try reducing physical activities.
• Reducing stress and anger. Anger and stress activate the sympathetic nervous system and cause high blood pressure, as if in a “fight or flight” situation. If anger and stress regularly trigger angina, a stress-reduction program or meditation can help.
• Exercising regularly. A supervised exercise can safely strengthen the heart and gradually reduce angina.
• Having a healthy diet. A healthy diet can fight the cholesterol-filled plaque in atherosclerosis, which is responsible for angina. It can lower weight, blood sugar, and cholesterol levels. Eventually, it will reduce angina.

Is angina life-threatening?

Angina itself is not life-threatening. However, the underlying factors or diseases that it indicates can be life-threatening. Thus, it is crucial to address angina symptoms immediately and appropriately, such as going to the doctor, to avoid further complications.

References

Angina (Chest Pain). (2021). American Heart Organization. https://www.heart.org/en/health- topics/heart-attack/angina-chest-pain

Angina – Symptoms and causes. (n.d.). Mayo Clinic. https://www.mayoclinic.org/diseases- conditions/angina/symptoms-causes/syc-20369373

Angina treatment: Stents, drugs, lifestyle changes — What’s best? (2023, May 27). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/coronary-artery-disease/in-depth/angina- treatment/art-20046240

Cardiac Catheterization. (2023). American Heart Association. https://www.heart.org/en/health- topics/heart-attack/diagnosing-a-heart-attack/cardiac-catheterization

Harvard Health. (2021, September 21). Angina: Symptoms, diagnosis and treatments. https://www.health.harvard.edu/heart-health/angina-symptoms-diagnosis-and-treatments

Hermiz, C., & Sedhai, Y. R. (2023, June 6). Angina. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK557672/

National Library of Medicine. (n.d.). Angina. Chest Pain | MedlinePlus. https://medlineplus.gov/angina.html

What      is      Angina?      |       NHLBI,       NIH.       (2023,      June      30).               NHLBI,                NIH.

https://www.nhlbi.nih.gov/health/angina

Written by Paige Fernandez

Edited and Reviewed by Reuben J C. Los Baños, Ph.D.

Your arteries supply blood and oxygen to your heart muscle. The obstruction of your arteries results in Myocardial Infarction (MI). It is also known as a heart attack. Unattended can cause severe cardiac damage and even death. You can recognize symptoms earlier once you know the early warning signs of MI.

Early identification and treatment are critical for decreasing the severity of MI. Heart attacks are the most significant cause of mortality globally. Nonetheless, many people can avoid these cases with lifestyle changes and increased knowledge. Understanding these features will enable you to preserve cardiovascular health. You will also be able to identify signs needing prompt medical intervention.

Coronary artery disease (CAD) is one of the primary causes of Myocardial Infarction. MI happens when plaque buildup obstructs a coronary artery. This is a process called Atherosclerosis. With time, this occurs when a blockage of cholesterol forms inside the arterial walls. These substances cause the narrowing of arteries and delay blood flow. Over time, the plaque hardens and reduces the space through which blood flows. If the plaque breaks, a blood clot can form at the site, completely blocking blood flow to the heart muscle. Other causes of MI include Coronary Artery Spasms and Spontaneous Coronary Artery Dissection.

Coronary artery spasms are sudden tightening of the walls within a coronary artery. The constriction can cut off the blood flow, which causes the oxygen for the heart muscle to no longer flow. But, these spasms are brief and can result in chest pain or even a Myocardial Infarction (heart attack). Several factors trigger coronary artery spasms, including:

• Drug Use. Stimulants like cocaine can cause spasms when blood pressure and heart rate increase. Cocaine is notorious for inducing extreme vasoconstriction. It also adds to the likelihood of spasms even in normal arteries.
• Extreme and Constant Stress. When your body is under stress, it releases adrenaline and stress hormones. They may then cause muscles around the coronary arteries to spasm. People with high blood pressure may suffer spasm attacks at times of intense stress.
• Cold Exposure. Sometimes, cold weather constricts the blood vessels and causes spasms.
• Smoking. Nicotine also induces vasoconstriction. This increases the probability of coronary artery spasms, particularly in chronic smokers.

An example of Coronary Artery Spasms is Variant Angina (Prinzmetal’s Angina). This is a type of angina due to coronary artery spasms. Unlike angina, which occurs with physical exertion, variant angina can occur at rest. Variant Angina often happens in the early morning. They can induce agonizing spasms that resemble the discomfort of an MI.

Cocaine-induced coronary spasm is another example. A person using cocaine may undergo sudden spasms that present as severe chest pain. That’s because not only does it constrict the blood vessels, but it speeds up the heart rate. Additionally, it raises blood pressure, which strains the heart.

Spontaneous Coronary Artery Dissection (SCAD) is a rare but severe disorder involving the coronary artery wall. This tear can cause a blockage of blood flow to the heart. Blood pools between the layers of the artery wall and creates a blockage.

SCAD occurs most in younger women without the usual ‘heart attack’ risk factors. Potential causes and contributing factors include:

• Hormonal Changes. SCAD connects to pregnancy or childbirth. It appears more common during pregnancy and the perinatal period after birth.
• Physical or emotional stress of great intensity. SCAD also occurs due to high stress levels. Stress levels vary, whether it’s stress induced by exercise or emotional trauma.
• Inherited Connective Tissue Disorders. Ehlers–Danlos syndrome and Marfan syndrome affect the structure of blood vessel walls. People with these inherited disorders are susceptible to SCAD.

SCAD examples include Postpartum SCAD. For many women, SCAD occurs in the weeks or months after giving birth.

Exercise-induced SCAD is another example. Individuals who do strenuous activities may exhibit SCAD episodes. These episodes happen before any other symptoms of cardiac disease.

Uncommon but life-threatening causes of heart attacks include SCAD and coronary artery spasms. Recognition of these conditions can help recognize the symptoms of Myocardial infarctions.

As a preventable condition, CAD helps you understand how to take proactive steps to lower MI risk. Managing atherosclerosis factors can reduce your chance of experiencing a Myocardial Infarction.

What Are the Warning Signs of a Myocardial Infarction?

Common warning signs include chest tightness, shortness of breath, dizziness, and upper-body pain. Early recognition of Myocardial Infarction symptoms can save a life. Immediate treatment can cut heart damage in half. The following are typical symptoms:

• Chest Pain or Discomfort. Chest discomfort is a sensation of strain or pressure that spreads from the arms to the back.
• Shortness of Breath. It can be a warning sign for difficulty breathing, sometimes without effort.
• Perspiration and dizziness. Some people get sudden sweating or nausea, like severe anxiety or indigestion.
• Upper Body Discomfort. Chest pain may come with discomfort in areas like the shoulder, back, and stomach, or it can go alone.

Women, diabetics, and older individuals are more likely to have atypical symptoms. These symptoms include:

• Back Pain. Problems with your back are often misinterpreted as muscle pain, but they can also display MI.

• Unexplained Fatigue. Sudden, unexpected fatigue can also come before a heart attack, especially in women.
• Lightheadedness. It may mean the blood isn’t flowing well, as an impending or happening MI brings.

Symptoms vary and may not manifest in you the way they would manifest in another person. Nonetheless, a rare or delayed onset of MI symptoms might have destructive outcomes. Additionally, it results in delayed detection of the medical emergency. Knowing these variations can help you start treatment on time.

What Is the First Marker of Myocardial Infarction?

The first and more sensitive marker of a myocardial infarction is troponin. Myocardial infarction requires cardiovascular biomarkers for its diagnosis. Of these markers, troponin is the most sensitive and specific. Troponin levels rise when there is damage to heart muscle cells. They become identifiable in the blood in a few hours following an MI and continuing high for a period of two weeks.

An example of high-accuracy testing is troponin testing. Medical providers use it to detect even the most minor heart muscle damage. Other markers that can state Myocardial Infarction include:

• Creatine Kinase-MB (CK-MB). The less exact version of troponin rises within hours to confirm heart muscle damage.
• Myoglobin. Myoglobin is an early marker and is always used together with other tests.

Elevation of cardiac troponin levels may not occur for hours after symptoms develop. Additionally, the window of opportunity for successful intervention is brief. Prompt detection affords a timely diagnosis and facilitates physician intervention. This limits heart muscle damage and improves patient outcomes.

What Tests Confirm a Diagnosis of Myocardial Infarction?

Myocardial infarction diagnosis combines ECG, blood testing for cardiac enzymes, and imaging examinations. Many tests look at heart function and blockages. These tests include:

• Electrocardiogram (ECG). This test records the heart’s electrical activity and patterns that suggest an MI. It can reveal poor blood supply and heart rhythm problems.
• Blood Tests. Troponin and CK-MB values make way for the confirmation of a Myocardial Infarction. Through this, healthcare providers will identify the extent of cardiac damage.
• Imaging Studies.
  • Echocardiography. Echocardiography is an ultrasound test of heart muscle function. This ultrasound test looks for the areas affected by the Myocardial Infarction.
  • Coronary Angiography. This imaging test uses dye to detect blockages in the coronary arteries. But, it is often done in emergencies.

A combination of diagnostic tools increases accuracy and also makes treatment better. Healthcare providers use many diagnostic methods to create treatment plans. These treatment plans aim to mitigate recovery and survival rates.

Who Is Most at Risk for Myocardial Infarction?

Individuals who have high blood pressure and high cholesterol are at risk of MI. Individuals who smoke and have family histories of heart disease are also at risk. Most of the risk factors associated with MI include those of lifestyle and genetics. Major risk factors include:

• Hypertension. Blood vessels damaged by high blood pressure increase the risk of MI.
• High LDL Cholesterol. Elevated cholesterol leads to debris development in the arteries.
• Diabetes. Elevated blood glucose levels damage your blood vessels and increase the risk of MI.
• Smoking. Tobacco use raises blood clot risk and helps create plaque.
• Family History. People prone to heart disease are likely to suffer a myocardial infarction.

Other factors include age, sex, obesity, and lack of physical activity. Risk is more significant in men early on but rises after menopause in women. The risk of MI is best monitored and managed through lifestyle changes. You can also use routine screening and medication if necessary. Taking preventive measures means you get to act to control your heart health.

Can Stress Cause a Myocardial Infarction?

Stress increases blood pressure, inflammation, and risk of plaque rupture. This can contribute to the development of a Myocardial Infarction.

Physiological responses to stress affect the health of the heart. When you are under stress, hormones like cortisol and adrenaline activate the body. These hormones increase your heart rate and blood pressure. With continued responses, these may increase the occurrence of hypertension and plaque instability. Thus increasing the chance that you will have a heart attack over time. It is a modifiable risk factor for developing CAD and increasing the incidence of MI.

Exercising, meditating, and being mindful can help you manage mental and physical stress. Efforts at regular stress management can help lessen MI risk. This protects your arteries and arterial damage and lowers your blood pressure. Regular stress management contributes to cardiovascular health.

Can Sadness Cause Myocardial Infarction?

Sadness on its own doesn’t exactly cause a Myocardial Infarction. But, it can lead to something called ‘broken heart syndrome.’ This mimics heart attack signs as well as its symptoms.

Intense emotional stress, such as grief, can weaken the heart muscle. This leads to the condition known as ‘broken heart’ syndrome or Takotsubo cardiomyopathy. Often, the symptoms resemble those of a heart attack — chest pain and shortness of breath. Broken heart syndrome is usually temporary but can become serious if not addressed. Individuals with pre-existing heart conditions are susceptible to ‘broken heart’ syndrome.

Prolonged sadness and depression may increase MI risk. This is because it contributes to high blood pressure and other risk factors. Research finds a link between the mind and the heart. It supports a holistic approach to heart health that includes emotional well-being. Providing support for emotional health may help with improved heart health. Additionally, it promotes better resilience after traumatic events.

Reducing MI risk requires investing in mental health through support and self-care practices. Besides being essential for quality of life, emotional well-being also impacts your heart.

Conclusion

Myocardial infarction results when there is an obstruction in your coronary arteries. This, in turn, decreases blood and oxygen flow to the cardiac muscle. MI can cause heart failure if not treated. Knowing the factors that may put you at risk for MI may help you detect it early and even save your life.

Preventive approaches have led to a reduction in MI risk. Good dietary habits and regular physical activity will keep your heart healthy. Regular screenings and check-ups can also help detect problems before they worsen.

Understanding, education, and proactive cardiovascular care lay the groundwork for long-term heart health. Recognizing the precursors of MI will better equip you to protect your heart. Through this, you will lessen the likelihood of life-threatening events like Myocardial Infarction. In the long run, these actions must be dominant enough to prevent casualties. Through finding problems earlier, intervening on time, or committing to preventative care.

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