Stomach is a J-shaped, hollow, muscular bag, situated after the esophagus of alimentary tract. It is the widest organ of digestive tract and has vital role in digestion.
Stomach has four parts: 1. Cardiac part
4. Pyloric part
- For its wide, hollow appearance stomach acts as a temporary storage for food, which passes from the esophagus.
- It churns and breaks up food and mixes the small food particle with the gastric juice by contraction and relaxation of the muscle layer in stomach.
- The main role of stomach is digestion. It secrets pro-enzyme like – pepsin and pro-renin, and enzymes as- gastric lipase, amylase etc.
Main gastric glands are found in the body and fundus of stomach. These are simple tubular glands which take part in the secretion of various digestive enzymes . The alveoli of these glands contain two types of cell- A. Chief cells and B. Parietal cell.
A. Chief cell secretes proteolytic proenzymes, pepsinogens etc.
B. Parietal cell also known as oxyntic-cell secretes hydrochloric acid (HCL) and intrinsic factor.
4. Partial digestion of proteins and fats take place here.
5. Stomach also plays a vital role in absorption. It produces a glycoprotein, known as Castle`s Intrinsic factor which is very necessary for the absorption of vitamin B12, in intestine. It is also help in the absorption of water- and water-soluble substances like Na+, K+ etc.
6. stomach also has a antiseptic function. HCL in gastric juice kill bacteria and other microbes. So it also helps to protect our body from microbes and takes part in our defense system.
In spite of these, stomach has many other functions, but among them -Secretion of stimulating substances like, gastrin, enterogastrone etc and Excretory function (excretion of certain toxin, alkaloids) are mostly notable.