Written by Kheizaya Methuzela G. Aguirre

Reviewed by Dr. Reuben J C. Los Baños, Ph.D.

Histology includes studying tissues and cells under a microscope. Histologists perform this to diagnose and research disorders of the tissues. They make tissue diagnostics and assist doctors in patient care management.

People study histology to:

• Examine the contents of the tissue.
• In agriculture, they seek what chemicals are present in the soil.
• Perform autopsies in this field. It is to comprehend better some inexplicable deaths during autopsy and forensic investigations. Microscopic tissue analysis may reveal a cause of death in some circumstances.

Why is it called histology?

Histology is a study that deals with cell and tissue structure at the microscopic level.

Its name comes from the Greek term “histos,” which means tissue or columns. The other is “logia,” which refers to “study.”

Histology first appeared in a book written by Karl Meyer in 1819. It was where he combined the two Greek words. And it was then traced back to the 17th century by Marcello Malpighi.

He experimented with insects, botany, and embryology as a scientist. He was the first to use the silkworm as a model to study insect respiration.

He also further investigated the development of chick embryos than anybody else. His experiments are what made him a pioneer in the science of embryology.

But it was his delineation of pulmonary capillaries and alveoli that made him famous. Using only a single magnifying lens, Malpighi saw pulmonary capillaries in the frog.

He termed these capillaries as “nature’s microscope.” It allowed him to see things that are not present in big animals.

Although he uses these single lenses in most of his findings, he also utilized a new microscope. This new type is the compound microscope, which arose at the end of the 16th century. It allowed him to see chick embryo development.

Here are some human body structures named after Malpighi:

1. Malpighian corpuscles
2. Malpighian layer in the skin
3. Malpighian tubules of the insect’s excretory system

How is tissue classified?

Tissues refer to a collection of cells with similar structures and play a specific role. Histology focuses on tissues’ appearance, structure, and function under a microscope.

Below are the classifications of tissues based on their structural and functional similarity:

• Epithelium
• Connective
• Muscular
• Neurological systems

The fundamental tissue collaborates to assist the human body’s general health and maintenance. As a result, any change in tissue structure might result in harm or illness.

Epithelial tissue is the body’s outer cover, lines interior cavities, and forms glands. As its name indicates, connective tissue ties the body’s cells and organs together.

When the body stimulates muscle tissue, it contracts, allowing mobility. Nervous tissue is also reactive. It enables electrochemical signals to generate and propagate into nerve impulses. When this happens, it communicates to the different parts of the body.

What are examples of tissues?

In histology, we all know that there are four types of tissues:

• Epithelial
• Connective
• Muscle
• Nervous

• Each of these tissues has examples of their structure and biological function. Under the epithelial tissue, you have the following:

• Simple Squamous
• Simple Cuboidal
• Simple Columnar
• Transitional
• Stratified Squamous
• Stratified Cuboidal
• Stratified Columnar
• Pseudostratified Columnar

The simple squamous allows items to flow through diffusion and filtration. It also emits lubricating substances. It resides on the lining of the heart, blood vessels, and lymphatic vessels, as well as the air sacs of the lungs.

Simple cuboidal epithelium ingests and secretes. It is in ducts and secretory parts of tiny glands and kidney tubules.

Simple columnar consumes and releases mucus and enzymes. They are on ciliated tissues like lungs, uterine tubes, and uterus. The digestive tract bladder also contains smooth (nonciliated tissues).

Transitional epithelium allows for the expansion and stretching of the urinary organs. The bladder, urethra, and ureters are all lined with it.

Stratified squamous epithelial tissue is the skin protector against abrasion. The esophagus, mouth, and vaginal canal are all lined with this substance.

Stratified cuboidal is present in sweat, salivary, and mammary glands. All these mentioned glands have a protective epithelial layer.

The stratified columnar epithelium is an uncommon kind of epithelial tissue. It has quite a few layers of column-shaped cells. The conjunctiva, throat, anus, and male urethra are some places where it situates. It also occupies the embryo.

Pseudostratified columnar epithelia are tissues that constitute a single layer of cells. But, they appear to look like they are of many layers when seen in cross-section. These epithelial cells’ nuclei are at various levels, giving the appearance of stratification.

• Connective tissue is another type of tissue that functions as a linking role in the body. It works to support and bind other tissues.

Examples of specialized connective tissues are:

• Adipose
• Cartilage
• Bone
• Blood
• Lymph

Adipose tissue is a fat-storing connective tissue. It protects organs and insulates the body from heat loss by lining organs and cavities in the body. Hormones produced by this affect blood coagulation, insulin sensitivity, and fat accumulation.

Cartilage is a tissue composed of packed collagenous fibers encased in chondrin. This chondrin is a rubbery and gelatinous material. Sharks and human embryos have cartilage in their bones. It offers flexible support for tissues such as the nose, trachea, and ears in mature humans.

Collagen and calcium phosphate, a mineral crystal, are all seen in bone tissue. It is a mineralized connective tissue made up of calcium phosphate for hardness.

Scientists classify blood as a form of connective tissue. It originates from the mesoderm, the central germ layer of growing embryos. The blood also functions to connect different organ systems. It carries signal molecules between cells to supply them with nutrients.

Another form of fluid connective tissue is lymph. Blood plasma exits blood vessels at capillary beds, resulting in this transparent fluid. It contains immune system cells that defend the body from infections.

• And for the muscle tissues, below are the examples that you must know about it:
• Smooth muscle
• Skeletal muscle
• Cardiac muscle

Smooth muscle is present in the intestines, blood vessels, urinary and reproductive systems. It contracts, causing peristaltic movement and blood vessel obstruction in the alimentary canal.

From the word “skeleton,” skeletal muscle links to the bones of our arms and legs. Voluntary motions involve the skeleton. To move bones, they contract and relax.

Cardiac muscle is a kind of muscle found in the heart. It settles in the heart’s walls where its cardiac muscle tissues are. They contract to pump blood to every region of the body.

• Nerve cells and their associated neuroglia cells make up nervous tissue. These cells receive and send nerve impulses or action potentials from one nerve cell to the next.

Dendrites and axons are two types of cellular projections found in nerve cells. The electrochemical signals are all received by the dendrites (from another nerve cell). The action potential will then forward to the next nerve cell via the axons.

The axon terminal is a bulb-like terminus to the axon. This axon terminal releases neurotransmitters that go to the next nerve cell of the body. It is to finally pass the nerve impulse from one nerve cell to another.

Neuroglia cells lie in the nervous tissue like the nerve cells. These cells assist in the protection and nourishment of nerve cells. They also aid in the maintenance of homeostasis and the formation of myelin.

The nervous system comprises nervous tissue. Nervous tissue comes in a variety of forms. Grey matter and white matter exist in the central nervous system. There are ganglion tissues and nerve tissues in the peripheral nervous system.

Where are the 4 tissues located?

Tissues are a bunch of cells with the same shapes and functions. Different organs contain different types of tissues. Listed below are the following four fundamental kinds of tissues found in humans.

• Epithelial
• Connective
• Muscular
• Nerve tissue

Within each of the primary tissues, there may be many sub-tissues. Each of them has its designated place in the human body where it operates. that you should know about.

Most inner cavities line epithelial tissue, covering the body’s exterior. The roles of epithelial tissue incorporate protection, secretion, absorption, and filtration.

An example of this is the skin protecting the body from dirt, germs, and other hazardous organisms. These tissue cells come in various forms – thin, flat, cubic, or elongated cells are all possible.

Connective tissues locate between other tissues everywhere in the body. They help bind structures to form frameworks and support organs. They store fat, carry chemicals, and guard against disease throughout the body. Additionally, they also help rectify tissue impairment.

Your muscle tissues are on your body’s muscles. These shorten or contract to produce motion of your body parts. The tissue is cellular and well-furnished with blood.

The nervous tissues in our body are all found in the brain, spinal cord, and nerves. They are in charge of supporting the nervous system in handling many functions.

How long does it take to become a histologist?

A histologist is someone who prepares tissue samples for examination by a pathologist. Its job is to cut tissue samples from organs or tissues and stain them with dyes. You use dyes to enhance the visualization of tissues for microscopic tissue examination.

There are times that you are also tasked to complete these activities immediately. Activities like taking a sample of tissue from a patient during surgery. You will also work on this when doing rapid laboratory analysis.

Becoming a histologist is quite long and requires patience. You must have either an associate or bachelor’s degree and a license to practice in the state where you work.

You may also need to earn certification from ASCP. Yet, this depends on your employer’s recommended job qualities.

This sector requires two years of laboratory experience. Thus, it necessitates meticulous attention to detail and knowledge of the equipment needed. Training in the handling of valuables is also part of the profession.

Students wishing to pursue this field must:

• Get a high school diploma and two years of histopathological clinical laboratory experience.
• Get an associate or bachelor’s degree in histotechnology.
• Finish at least a year of clinical lab experience in histotechnology.
• Get a license by passing the national examination.

Is histology a hard class?

Histology is beneficial to medical students in a variety of ways. It aids them in comprehending the typical organ system’s cell and tissue architecture. Furthermore, it links structure to function by tying tissue structure to operate.

Histology is somehow complex because it needs excellent memorization and understanding skills. But at the same time, it is a fascinating field of study. It’s amazing how intricate the tissues are while still being so similar.

You will still find the fascinating aspect of it. There is no single branch of biology that is very easy, with all honesty.

All fields need a thorough understanding because the scientific world is expansive. Yet, you won’t regret learning new things because uncommon ones are always interesting.

References:

Anatomy and Physiology: Four Types of Tissues. (n.d). https://open.oregonstate.education/aandp/chapter/4-1-types-of- tissues/#:~:text=Tissues%20are%20organized%20into%20four,maintenance%20of%20th e%20human%20body.

Classification of Tissues. (n.d). https://www.vedantu.com/biology/classification-tissue Goldberg, Alexander. 2018, December 18. A Brief History of Histology.

Helmenstine, Anne Marie. 2019, March 24. What Histology Is and How It’s Used. thoughtco/histology

Stoppler, Melissa Conrad. 2021, March 29. Medical Definition of Histology. Medicinenet/histology

ZipRecruiter Marketplace Research Team. (n.d). What Is A Histologist and How to Become One. Ziprecruiter/histology