Write a short note on the small intestine.

Explanation

The small intestine assists in the final digestion and absorption of food. It is the longest part of the alimentary canal and has three regions, a 'U' shaped duodenum (25 cm long), a long coiled middle portion jejunum ( `2.4` m long) and a highly coiled ileum (`3.5` m long ). The wall of the duodenum has Brunner's glands which secrete mucus and enzymes, lleum is the longest part of the small intestine and opens into the caecum of the large intestine. The ileal mucosa has numerous vascular projcctions called villi which are involved in the process of absorption and the cells lining the villi produce numerous microscopic projections called microvilligiving a brush border appearance that increase the surface area enormously. Along with villi, ilual u sa alsu Lulu US Secretig goblet cells and lymphoid tissue known as Peyer's patches which produce lymphocytes. The wall of the small intestine bears crypts between the base of villi called crypts of Leiberkuhn.