The digestive system plays a vital role in the survival of all living organisms because It includes all the organs through which digestion of food is completed. Food is the most critical component for energy and all the other processes in the human body.
Structure of stomach
The stomach of humans is J-shaped which is present in the middle of the chest. There are four layers around the gut. The first layer is called serosa and the second layer is the Muscularis layer.
The Muscular layer is further divided into three layers longitudinal, muscles, and oblique muscle layer after the muscular layer mucosa layer is present and after that submucosa layer.
There are two ends of the stomach cardiac sphincters and pyloric sphincters. The cardiac sphincter is the end between the esophagus and stomach, and the pyloric sphincter is the end that connects the stomach with the small intestine.
The stomach is divided into four regions cardiac region, pyloric region, fundus, and body.
The cardiac region connects the stomach with the esophagus. The fundus is an expanded area of the stomach. The most significant part of the stomach is the body and the pyloric is the narrow region of the stomach.
The wall of the stomach has millions of gastric glands which produce gastric juices after eating food. The gastric glands have several cells such as partial cells, chief cells,mucus-secreting cells, and hormone-secreting cells.
Parietal cells produce HCl, which makes the stomach environment acidic and kills microorganisms. Cheif cells have pepsinogen. When pepsinogen combines with Hcl, it forms a protein-digesting enzyme called pepsin.
Mucus secreting cells produce mucus which protects the stomach wall from acidic damages.
Hormones secreting cells produce hormones. For example, they have a hormone called gastrin Which stimulates the secretion of gastric glands.
The human stomach can release about 400-800ml gastric juices.
Digestion of food
The digestion of food starts from the mouth. Salivary glands produce saliva, which moistens the food and also kills bacteria from the food. After the breakdown of food in the mouth, the food passes through the esophagus into the stomach. An essential function of the stomach is That it can store food, that's why we can eat a lot of food digested slowly by the stomach.
In the stomach, the first charge of food occurs; for this purpose, the stomach releases gastric juices such as HCl and digestive enzymes. In the stomach, large protein molecules are converted into small amino acids.
After all this, the food in the stomach is converted into a thin liquid called Chyme.
The absorption of food, carbohydrates, and water doesn't occur in the stomach. But iron and highly fat-soluble substances such as alcohol are directly absorbed in the stomach.
The liquid Chyme through the pyloric sphincter moves to the first part of the small intestine called the duodenum. After that, the food moves to the second part, jejunum and then Illum; from here further, digestion occurs in the small intestine.
In the small intestine, food is further converted into the smallest particles. The absorption of digested food occurs in the small intestine. Tiny hair-like structures called villi helps in the absorption of food. From villi, the food particles inter into capillaries and mix with blood.
The absorption of water and sodium occurs in the large intestine. The first part of the large intestine is called the cecum. The Appendix is also present in the large intestine.
After digestion and absorption, the waste material from the rectum to the anus leaves the body.
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