Digestion and Absorption

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Longest part of gut (7 m long and 2.5 cm diameter).

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Consists 3 parts, namely duodenum (C shaped first part 25 cm

long), Jejunum (middle part 1 m long, coiled) and Ileum (terminal

part 2 m long, highly coiled). (NEET 2020)

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Finger-like villi are seen at the mucosa. Each villus has a brush-

bordered columnar epithelial layer provided with microvilli. Villus

consists of a capillary network and a small lymph vessel (lacteal).

SMÅLL ÏÑTËSTÏÑË :

1.5 m long. Consists of caecum, colon and rectum.

Caecum is well-developed in herbivores but in man it is very small.

Arising from the caecum is a finger-like vestigial organ, the vermiform

appendix.

The colon consists of ascending colon, transverse colon, descending

colon and sigmoid part (opens into the rectum)

Sigmoid or pelvic colon leads to rectum that opens out by anus. Anus is

guarded by sphincter (circular voluntary muscles).

In some herbivores, the large intestine consists of several cellulose

digesting bacteria.

LÅRGË ÏÑTËSTÏÑË

HÏSTØLØGÝ ØF HÜMÅÑ GÜT (TRÅÑSVËRSË SËÇTÏØÑ)

HÜMÅÑ GÜT ÏS FØRMËD ØF 4 LÅÝËRS

1

Mucosa : Innermost, moist epithelial layer. Contains secretory

(E.g. Gastric glands in stomach and crypts of Lieberkuhn in

intestine (NEET 2019) and absorptive cells. (E.g. villi in small

intestine). Mucosa Associated Lymphatic Tissues (MALT) is

present on the lining of mucosa layer. Villi are supplied with a network of

capillaries & large lymph vessel called the lacteal.

2

Sub-mucosa : Soft connective tissue layer just outside the

mucosa. Nerves and blood vessels are present. In duodenum,

glands are also present in sub – mucosa.