Everything you need to know about stomach its functions and mechanism of digestion in stomach

The mammalian stomach is a muscular distencible sac.


Functions of stomach


Stomach performs three important functions

  1. It receive food in the form of bolus from esophagus. It stores this food.

  2. Stomach secretes substances ( Enzymes, mucus and hydrochloric acid (HCl). These substances initiate (starts) digestion of proteins.

  3. It control the rate of movement of food into small intestine through pyloric sphincter.


Gastric Glands and Gastric Juice


The stomach is composed (made up of) of inner mucous membrane. This membrane comprise (contains) thousands of glands. The gastric glands have three  types of cells are:

  1. Parietal cells: These cells secretes hyrochloric acid (HCl).

  2. Chief cells: They secretes pepsinogen. Pepsinogen is converted into Pepsin enzymes. Parietal cells and Chief cells are exists in the pits of gastric glands.

  3. Mucous cells: Mucous cells are present at the exterior surface of gastric glands. They secretes mucous. Mucous form a coat on the inner surface of gastric glands. This coat protects the wall of stomach from the action of HCl and Pepsin.


The upper (superior) surface of gastrointestinal tract i.e. esophagus and mouth have a much thin mucous cell layer than stomach. Therefore, vomiting cause a burning sensation in the esophagus or mouth. Endocrine cells are present in one part of the stomach mucosa. They release hormone gastrin. It travels to the target cells in the gastric glands and further stimulates them.


Mechanism of digestion in stomach


When mass of  particles of food enters the stomach. It spread or extends the walls of stomach. This distention (spreading) stimulates the gastric pits to secretes HCl and pepsinogen. The H ions converts the pepsinogen into active enzyme pepsin. The smooth mucosal muscles contract. Therefore pepsin, mucous and HCl mix with food. Pepsin breaks down proteins. The stomach contents are sufficiently (suitably) mixed after one eighty minutes. It synthesize a liquid mass called chyme. The pyloric sphincter adjust (regulates) the release of the chyme into the small intestine.

The peristaltic waves terminate or cease when the stomach is empty. But new waves starts in the upper region of the stomach after ten hours of fasting. These waves can because of hunger pangs.

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