Written by Francine Marianne A. Caseres

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

Made up of complex networks of cells, your digestive system is a vital organ that you can’t live without! You’re able to absorb nutrients and excrete waste through this system. And with it, you’re able to complete your daily tasks and get through the day. 

This complex system has many histological aspects that are essential for its actions. Among these are your different cells, histological layers, and others. Let’s discuss these one by one! 

The digestive system has your alimentary canal. It also has your accessory digestive organs. These include the salivary glands, teeth, pancreas, liver, and gallbladder. These are all necessary so that they may help in the digestion of food. 

Intestinal Cells 

Among the most significant cells present are the epithelial cells in your intestines. The columnar epithelium helps absorb the nutrients needed in our body. As well as enterocytes, goblet cells, Paneth cells, and enteroendocrine cells. 

Enterocytes 

Involved in the chemical digestion of food, these cells line the intestines. They also form the brush border, which is a barrier for the absorption of food. This includes their ions, water, and nutrients. 

Goblet Cells 

These cells secrete mucus, which protects and lubricates the intestines. 

Paneth Cells 

The Paneth cells are in charge of the small intestine’s germ-killing output. They also help renew the intestine’s lining. 

Enteroendocrine Cells 

They aid in digestion by secreting many peptide hormones. They also regulate intestinal motility and food intake. 

Stomach Cells 

Many types of cells are also found on the stomach. Their main job is to break down materials using acid and enzymes. The stomach has four cell types. They are the chief, mucous neck, enteroendocrine, and parietal cells. 

Chief Cells 

These cells secrete pepsinogen, which breaks down proteins when activated.  

Mucous Neck Cells 

These types of cells located in the gastric glands of the stomach secrete acidic mucus. 

Enteroendocrine Cells 

These cells in the stomach differ from those in the intestine. In the stomach, these cells can secrete hormones, particularly gastrin. Gastrin’s main function is to make the stomach secrete hydrochloric acid. This acid kills bacteria and helps digest food. 

Parietal Cells 

These cells produce hydrochloric acid and the intrinsic factor. This factor enables the absorption of vitamin B12. 

What are the histological features of the digestive system?  

The digestive system can take in food. It absorbs nutrients and removes indigestible materials.  

Aside from the different cells in the digestive system, this system also has two types of organs. Some belong in the GI tract. Others belong in the accessory organs. All these play a huge part in your body’s functions.  

The GI tract has many parts. These include the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.  

• Mouth – The mouth aids in the mechanical processing of food. The cheeks, tongue, uvula, hard palate, and soft palate form this. They’ve mixed food with saliva. 

• Pharynx – Its pharyngeal muscles propel materials into the esophagus. It is composed of skeletal muscles and is covered with mucus. 

• Esophagus – The esophagus transports materials to the stomach. Including the transportation of bolus from the mouth to the stomach. This 25-centimeter tube starts from the interior end of the laryngopharynx.  

It then ends at the superior part of the stomach. 

• Stomach – This organ aids in the chemical breakdown of materials. It has four main regions namely, the cardia (surrounds superior opening), fundus (left to the cardia), body (large central portion), and pylorus (connects the stomach to the duodenum).  

• Small Intestine – This aids in the enzymatic digestion and absorption of water, vitamins, ions, and organic substrates. The small intestine also has three major parts namely the duodenum, jejunum, and ileum. These will be discussed later on.  

• Large Intestine – The colon, the cecum, the anal canal and the rectum are the four major regions that compose the large intestine. It dehydrates and compacts undigested food materials, in preparation for elimination. 

• Anus – This is the last part of the GI tract and lubricates the passage to help the feces pass through smoothly. 

The accessory digestive organs also aid in digestion. These are the salivary glands, teeth, pancreas, liver, and the gallbladder. 

• Salivary glands – These glands secrete fluid that help breakdown carbohydrates. They release saliva into the oral cavity for this purpose. The three types of glands are the parotid, submandibular, and sublingual glands. 

• Teeth – Teeth aids in cutting, tearing, and pulverizing solid food. 

• Pancreas – This organ secretes digestive enzymes to digest protein. They also secrete a certain hormone, insulin, to control blood sugar levels of your body. 

• Liver – This organ secretes bile which is important for lipid digestion. They also store nutrients. Located just below the diaphragm, this is the 2nd largest organ in the human body. 

• Gallbladder – The gallbladder acts as the storage for bile. It is located beneath the liver and is a small, pear-shaped organ. 

Most of the digestive system is also composed of four histological layers. These four distinct layers are all vital to its function. These are the mucosa, submucosa, muscularis externa, and the serosa. 

Mucosa 

This is the digestive system’s innermost layer. This has loose connective tissue and simple columnar epithelium with goblet cells. These are all divided into different layers of the mucosa. 

The three layers are the epithelium, the lamina propria, and the muscularis mucosae. The lamina propria is a type of loose connective tissue. This muscularis mucosae takes part in the formation of folds. 

Submucosa 

The second layer supports the mucosa. It’s rich in blood vessels, nerves, and lymphatic vessels. This is also made up of dense irregular connective tissue. 

Muscularis externa 

Two layers of smooth muscle compose the muscularis. This layer is responsible for the peristalsis movement of the digestive system which is controlled by the nerve plexus. 

Serosa 

A simple squamous epithelium makes up the outermost layer of the digestive system. It also can also have a small amount of underlying loose connective tissue.  

What is the stomach cell that produces gastric acid? 

Hydrochloric acid makes up gastric acid, which aids in digesting food. The cells that produce it are the parietal cells. The parietal cells are located in the proximal two-thirds, or body of the stomach. 

What are the histological layers of the stomach?  

The stomach is part of the digestive system. It’s in the gastrointestinal (GI) tract, which compromise most of the system. It has four distinct layers, just like the layers of the digestive system. These are the mucosa, submucosa, muscularis, and the serosa. 

Mucosa 

This is the stomach’s innermost layer. It releases digestive juices through its glands.  

Submucosa 

The second layer supports the mucosa. It’s rich in blood vessels, and contains the submucosal nervous plexus. 

Muscularis 

This helps mix the food with digestive juices in it. 

Serosa 

This is the outermost layer of the stomach. This layer also confines the stomach as it wraps around it. 

What is the stomach cell that produces gastric acid? 

Hydrochloric acid makes up gastric acid, which aids in digesting food. The cells that produce it are the parietal cells. The parietal cells are located in the proximal two-thirds, or body of the stomach. 

What is the histology of the duodenum? 

The duodenum is actually found in the first part of the small intestine. In this region, the body mixes bile and digestive juices with the food to aid in further digestion. Vitamins, minerals, and other nutrients are also absorbed here. 

The duodenum is like other GI organs. It has the mucosa, submucosa, and muscularis layers. The duodenum has a unique feature. It has microvilli, villi, and Brunner’s glands. 

Microvilli  

Actin filaments support the microvilli. They are protrusions on the surface of different cell types. 

Villi 

Villi are small projections. They enable maximum nutrient absorption by increasing surface area. 

Brunner’s Glands 

Cuboidal and columnar cells make up these glands and secrete neutral mucin. These glands are also similar to the glands in the distal gastric mucosa and periampullary region. But, they have a nodular appearance on the mucosal surface. 

What is the histology of the jejunum? 

You call the middle region of your small intestine the jejunum. Proteins, fats, cholesterol, and water absorb here. Like your whole small intestine, the jejunum has its own mucosa, submucosa, muscularis, and serosa layers.  

The jejunum has key features. They are the Lieberkuhn crypts and villi. The intestinal lumen contains them.  

Lieberkuhn crypts 

These crypts are tubular glands. They secrete intestinal juice and are formed from the mucosa at the bases of the villi. You can also find Paneth cells and stem cells in these crypts. 

What is the role of the large intestine in the digestive system?  

The large intestine, also known as the colon, plays an essential role in your body. The rectum and anus are also in your large intestine. They’re important in fulfilling the activities of your daily lives.  

But first, what exactly is the large intestine? 

It’s in the last part of your GI tract. Mainly, it absorbs water and eliminates solid waste. Dehydration and the compaction of indigestible materials also happen here. They’re prepared for elimination. 

Your large intestine is 1.5 meters long. It extends from the cecum to the anus. The large intestine has four main parts: the cecum, colon, rectum, and anal canal. 

Cecum  

The cecum is a small pouch-like organ that is present next to the ileocecal sphincter. The cecum’s main job is to get food from the small intestine. It then moves the food to the large intestine. 

Colon 

This is where the final absorption of water and electrolytes takes place. The colon secretes mucus to bind and lubricate food waste. This helps it pass through the intestine smoothly. 

Rectum  

This composes the last 20 centimeters of the GI tract. In this region, the food waste, now in the form of feces, triggers the urge to defecate. Defecation, in turn, is so important for our body so we may be able to get rid of our own toxins. 

Anal Canal 

As feces leaves your body, it travels through your anus, marking the end of the digestive cycle. 

What are the major histological features of the large intestine?

The large intestine is made of columnar epithelial cells. They are able to absorb materials well. It also has many goblet cells, basal stem cells, and endocrine cells. Yet, there is no striated border nor Paneth cells.  

Like the small intestine, the large intestine also has its own histological layers. These include the mucosa, its lamina propria, submucosa, and muscularis externa. 

Like that of the small intestine are the lamina propria and submucosa. 

The muscularis externa is different from the small intestine, in contrast. It is arranged in three long bands called taenia coli. 

Lastly, the mucosa has no villi, unlike other structures of the digestive system. But instead of villi, the large intestine has crypts. 

The Digestive System as a Whole 

Together with the GI tract and accessory organs, they make up your digestive system. And your body would function poorly without it.  You may not be able to enjoy tasting and eating food, nor excrete the toxins of your body. 

Constipation, the lack of bowel movement, is also common. It affects one-third of adults over 60. In fact, without treatment, severe constipation can lead to bowel problems. In severe cases, it could lead to hospitalization, surgery, and even death. 

Thus, the role of our digestive system is essential in our lives. No one can live without it, and it’s up to you to take good care of this system. 

To eat a good diet and exercise regularly is one of the key things that can affect your body healthily. The histology of the digestive system is fascinating. All the cells and tissues involved would help you thrive. They enable your organs to work normally. 

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