The stomach, small intestine (little over 5 meter) and large intestine are suspended by mesenteries within the peritoneal cavity. The outer structure serosa is connected with the visceral peritoneum which in turn is surrounded by parietal peritoneum.
There is serous fluid located between parietal and visceral peritoneum which acts a shock absorber by reducing the friction between the two peritoneal layers. Apart from these there are other layers like muscular, submucosa, and mucosa. Stomach is a J shaped organ and consists of cardiac sphincter, pyloric sphincter, fundus, body, pylorus, lesser curvature, and greater curvature.
Functions:Stomach àStorage of ingested food, and mixing it with gastric juice, breakdown with churning movement, chemical digestion, limited absorption of fluids and drugs, defense against microbes, preparation of iron for absorption, production and secretion of intrinsic factor, regulation of the passage of the gastric contents into the duodenum, and secretion of the hormone gastrin. Small intestineà connects the stomach at pyloric sphincter and large intestine at ileocecal valve. It has 3 parts; duodenum, jejunum, and ileum. Onward movement of its contents by peristalsis is a major function of the small intestine. Other functions include secretion of intestinal juice, which help in the proper digestion of the contents. The stomach’s antimicrobial action of the hydrochloric acid does not kill all the microbes, so the small intestine protects us against those microbes; completes the chemical digestion of carbohydrates, proteins, and fats; secretion of hormone cholecystokinin (CCK), and absorption of nutrients are other main functions.Large intestineà also known as colon, connects the small intestine and rectum. It consists of four basic layers of digestive tract.
The functions are absorption of water, mineral salts, vitamins, and some drugs, synthesis of vitamin K and folic acid, mass movement by gastrocolic reflux, and defecation.