Sunday, March 6, 2016
HUMAN DIGESTIVE SYSTEM-PART-5-TEXT
Smallintestine – structure and functions of enzymes. Smallintestine is a tube of 6 meters length and 3cm width.
The anterior part is called duodenum. The middle part is called jejunum and posterior part is called ileum. Ileum joins large intestine. The middle part of intestine is coiled.
Cells present in the intestinal wall secrete mucous and enzymes in the form of intestinal juice. This is called succusentericus. Enterokinesis, peptidase, lipase, sucrose, nuleotidase, nucleosidase are some of the enzymes present in the intestinal juice.
Partially digested food entering the intestine mixes with the intestinal juice. Enzymes present in the intestine completely digested the partially digested food.
Peptidases convert peptides into amino acids. Intestinal lipase completely digests fats. Enzymes sucrose, maltase, lactase hydrolyse sucrose, maltase, lactase respectively converting them into glucose. Other sugars are also produced in this process. Nucleotidase and nucleosidase complete the digestion of nucleic acids.
Transport of the products of digestion from the intestine into blood is called absorption. Internally, intestinal wall has a number of finger like process called villi. The villi increase the surface area for absorption. Blood vessels are present in the form a network in the villi. Products of digestion are absorbed first into the villi and from there into the blood vessels and lymph vessels.
The diameter of large intestine is greater than the diameter of the small intestine. Large intestine is present between small intestine and rectum. The wall of colon is made of involuntary muscles. Movement of these muscles pushes the food large intestine.
Water and minerals salts present in the chime are absorbed in the colon and soft, solid faeces is formed. Faeces consists of undigested food material, dead material, bile salts and bile pigments. By the peristaltic movements of large intestine, faeces is pushed towards rectum. It is expelled out through the anus. This happens when the sphincter muscles that guard anus expand. This activity is called defecation.