Describe external structure of small intestine and large intestine.

Explanation

(a) Small Intestine : It is 6.25 m long tube, small intestine starts with stomach. It is surrounded by large intestine in belly button region of abdomen. It is divided into three parts.
(i) Duodenum : Starting part is of .U. shaped. It possesses 25 cm length.
(ii) Jejunum : It is a long coiled middle portion. It is 1 metre long
(iii) Ileum : It is the last part of small intestine and coiled part.
The opening of stomach into the duodenum is guarded by the pyloric sphincter.
Function : Digestion of food and Absorption.
(b) Colon : It is approximately 1.5 metre long. Colon opens into large intestine. It consists of caecum, colon and rectum.
Caecum is a small blind sac which hosts some symbiotic micro-organisms.
A narrow finger like tubular projection, the vermiform appendix which is a vestigial organ, arises from the caecum. The caecum opens into colon. It has three main parts.
(a) Ascending (b) Transverse (c) Descending
The descending part opens into the rectum which opens out through the anus.
Function : Absorption of water, salts and glucose.