Describe the structure of the small intestine and its role in digestion?


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Structure of the small intestine: 

  1. The small intestine is the longest part of the digestive system measuring about 20 ft. or 6.25 metres.
  2. It is present in the central and lower abdominal cavity.
  3. The inner surface is thrown into a series of circular folds.
  4. Villi are units of absorption of food which are present in the small intestine.
  5. Villi are more in the posterior region as compared to the anterior region.

It is divided into three regions:

Region

Length

Part of small intestine

Features

Duodenum

25 cm

Anterior

Widest part

For ‘C’ shaped curve and ends at a sharp bend called duodenojejunal flexure.

Jejunum

8 ft

Middle

Vascular and thicker wall

Villi thin and finger-like

Peyer’s patches absent

Ileum

12 ft

Posterior

Opening villi thin and finger-like.

Peyer’s patches guarded by caecal valve.

Role of small intestine:

  1. Muscles in the small intestines churn, kned and crush the food.
  2. They mix it with the intestinal juice and propel it forward to the large intestine by contraction.
  3. Completion of digestion and absorption of food takes place in the small intestine.
  4. Hormones like secretin, duocrinin, cholecystokinin, etc. are secreted by the small intestine.
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