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Comment upon large intestine.
Answer

Large intestine : It has a length of 1.5 m. It consists of caecum, colon and rectum. 

The large intestine has three parts :

1. Caecum : is a small blind sac which hosts some symbiotic micro-organisms. It is 8 cm in length. The caecum gives a blind tubular diverticulum called vermiform appendix. A narrow finger-like tubular projection, the vermiform appendix which is a vestigial organ, arises from the caecum.  The caecum and vermiform appendix are vestigial in man. The ileum opens into caecum ; the opening is guarded by ileocaecal valve. It checks the back flow of the food from caecum into ileum.

2. Colon : The caecum continues into colon. The colon has 3 parts - an ascending, a transverse and a descending part.

(a) Ascending colon : It runs towards anterior end of the abdominal cavity.

(b) Transverse colon : It runs horizontally and joins the two ascending and descending colons.

(c) Descending colon : It runs towards posterior side of the abdominal cavity and leads into sigmoid colon.

The colon has longitudinal groove called taeniae coli. On either side of taeniae coli there are pouches called haustera.

Functions :

i. In colon maximum amount of water is absorbed.

ii. Vitamin K and vitamin B are synthesised by the action of bacteria in colon.

(3) Rectum : It has a length of 12 cm. The rectum leads into anal canal which has a length of 2-3 cm. It opens outside via anus.