SMALL INTESTINE::
It is a coiled up tubular structure which consists of three parts:1.duodenum 2.jejunum and 3.Ileum from above downwards it is about 5-7 metres long
1.Duodenum::
The first part of the small intestine is a C-shaped tube the decending part of the duodenum contains openings of bile duct and pancreatic duct former carries bile and later the pancreatic juice They open jointly as a common bile duct bile is secreted from the liver it is stored and concentrated in the gall bladder pancreatic juice is secreted by the exocrine part of the pancreas the main function of duodenum is partial digestion of food
2. Jejunum::
It is the continuation of duodenum and it forms two fifth of the small intestine it is a coiled up structure and performs peristaltic movements because of its muscular coats it has innumerable glands which from the succus entericus juice it is bound behind by a fold of peritoneum called messentery whichm carries the blood vessels the autonomic nerves and the lymphatics to jejunum the main function jejunum is digestion of food it however also performs the function of absorption
3.iieu::
it is the distal three fifth of the long and coiled up small intestine it follows jejunum and ends at caecum which is the beginning of large intestine (colon) iieum has similar structure as jejunum but is has in addition many more villi
There are number of peyer s patches in ileum They are minute lymphoid structures which serve to defend against the microbial invasion iieum also contains digestive glands but they are less than that in the jejunum iieum performs the function of absorption more than that of digestion
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