Question

How does digestion happen in the stomach?

Answer 1

Stomach is an elastic muscular bag. The muscles of stomach walls mix up the food with gastric juice and convert it into chyme digesting it partly.

Explanation:

Stomach wall is composed of three principal layers:

• An outer layer of connective tissues

• A middle layer of smooth muscles:
  This layer consists of outer logitudinal and inner circular muscles. These muscularlayers help in churning and mixing the food ith stomach secretions.

• Inner layer of connective tissues also known as mucosa:
  This layer consists of numerous tubular gastric glands which are composed of three kinds of cells.
• Mucous cells `to`secrete mucous .
  Mucous is thick secretion. It covers inside of the stomach and prevents the underlying walls from being digested.
• Parietal or oxyntic cells `to` secrete hydrochloric acid`(HCL)`
  `HCL` is secreted in concentrated form. It adjusts the pH of stomach contents ranging from 2-3 for the pepsin to act on proteins. It also softens the food and kills the microorganisms present in it.
• Zymogen cells `to` secrete pepsinogen(Active form=Pepsin)
  Pespsinogen is an inactive form of pepsin. It is activated to pepsin when exposed to acidic medium(HCL) or to some already activated pepsin. Pepsin hydrolyzes proteins.

The secretions of all these cells are collectively called as gastric juice. Secretion of gastric juice is regulated by smell, sight and quality of food.

Thus, all the three layers of stomach perform their assigned tasks for the partial digestion of food into pulpy acidic fluid chyme. Eventually, the stomach empties into the duodenum through the relaxed pyloric sphincter.

`Note:`
Stomach is an organ of body which makes discontinues feeding possible by acting as a storage bag of food. Otherwise, we would have to eat continuously from dawn to dusk in order to live.