Histology of the Stomach

Also known as microanatomy, histology refers to the study of the microscopic structure of cells and tissues. The histology of the stomach can provide valuable information about the nature, extent and characteristics of gastric cancer cells. In this manner, it plays a key role in cancer diagnosis, prognosis and treatment planning.

For instance, histological examinations of cancerous stomach cells allow pathologists to identify the type of cells involved in the cancer and therefore provide an accurate diagnosis. Histology also helps to determine the grade and stage of gastric cancers, which is crucial in determining the aggressiveness of the cancer and planning appropriate treatment strategies.

Let’s take a deep dive into the histology of the stomach, focusing on the gastric glands and the cells that make them.

A gland is an organ that produces and releases substances with specific functions in the body. The gastric glands are located in the stomach lining. These glands perform a vital role in digestion, which is the process of breaking down food into smaller compounds that can be absorbed into the bloodstream.

Gastric glands are all located beneath invaginations called gastric pits, which open up into small holes on the surface of the gastric mucosa. Throughout the entire mucosa itself are millions of gastric pits that contain three to five gastric glands each. Secretions produced by the gastric glands are delivered into the stomach lumen through these gastric pits.

The gastric glands are made up of five main types of cells.

Surface mucous cells

These cells make up the gastric mucosa’s epithelial lining and are found around the opening of the gastric pit. They produce a thick, alkaline mucus that lubricates the entire mucosa.

This mucous coating protects the stomach lining from the corrosive nature of gastric acid or gastric juice, which contains potent hydrochloric acid and digestive enzymes like pepsin. It also minimizes the abrasion from food particles traveling through the GI tract.

Mucous neck cells

Mucous neck cells are found at the neck of the gastric pit, next to parietal cells. They are shorter than surface mucous cells and produce a thin, acidic mucus. These cells contain fewer mucin granules, which are secretory granules that hold a protein component of mucus.

Parietal cells

Also called oxyntic cells, parietal cells are mostly found on the gastric glands’ side walls. These cells release hydrochloric acid, which is the main component of gastric acid or gastric juice. Hydrochloric acid is necessary to stimulate the activation of digestive enzymes released in the stomach. It also helps kill any bacteria ingested with food and denature proteins to make them more amenable to enzymatic digestion.

Another substance secreted by these cells is intrinsic factor, a protein that binds to vitamin B12 and is essential for the vitamin’s absorption by the body.

In response to the release of histamine by nearby enterochromaffin (ECL) cells, parietal (or oxyntic) cells produce and secrete bicarbonate ions. These ions have a key role in the stomach’s pH buffering system.

Chief cells

Found near the base of gastric glands, chief cells secrete two substances called pepsinogen and prorennin. These substances are known as proenzymes or zymogens, which are the inactive precursors of enzymes. Pepsinogen is the precursor to the enzyme pepsin, which is responsible for digesting proteins. Hydrochloric acid is essential for the conversion of pepsinogen to active pepsin.

Meanwhile, prorennin, which is produced only in infants, is the precursor to the enzyme rennin. Rennin is another protein-digesting enzyme that curdles milk. Additionally, chief cells produce gastric lipase, an enzyme that contributes to the digestion of fat in our body.

Enteroendocrine cells

These cells are typically found in the basal regions of the gastric glands. They can be further classified into three types:

• Enterochromaffin-like (ECL) cells: These cells release the hormones histamine and serotonin. They store histamine and secrete it when the stomach pH is too high, which is triggered by the secretion of the hormone gastrin by the G cells. Histamine itself encourages the production and release of hydrochloric acid by parietal (or oxyntic) cells. When the pH level of the stomach decreases and the stomach environment becomes more acidic, ECL cells halt the release of histamine.
• G cells: These cells release gastrin into the bloodstream, which triggers the gastric glands to secrete gastric acid or juice. G cells are primarily located in pyloric glands, but some are found in the duodenum (first part of the small intestine) and other tissues. The gastric pits of pyloric glands are a lot deeper than other types of gastric glands.
• D cells: These cells secrete the hormone somatostatin, which controls the release of hormones and other gastric secretions.

These five types of cells make up the gastric glands, of which there are three types named after the regions of the stomach in which they are found.

Cardiac glands

These glands are located in the cardia, which is the region of the stomach closest to the esophagus. The cardia only contains cardiac glands and no other types of gastric glands. The predominant role of cardiac glands is to produce mucus secretions. This is important in protecting the stomach from the harsh effects of gastric acid and preventing the organ from digesting itself.

Fundic (or oxyntic) glands

These glands are located in the fundus and body (or corpus) of the stomach, where much of the chemical digestion takes place. They are mainly made up of mucous neck cells, parietal and chief cells, with some enteroendocrine cells.

They are classified as exocrine glands, which are defined as glands that release substances through openings onto a bodily surface. In this case, fundic glands secrete the components of gastric juice through the gastric pit and onto the surface of the gastric mucosa. Gastric acid or gastric juice is made up of various substances, such as hydrochloric acid, digestive enzymes (like pepsin and lipase), water, mucus and intrinsic factor.

Pyloric glands

Pyloric glands are found in the gastric antrum and pylorus. They are mostly made up of mucous neck cells and enteroendocrine cells. Pyloric glands are endocrine glands that secrete hormones, such as gastrin, directly into the bloodstream.