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 (2.4m long) and a highly coiled ileum (3.5 m long).
The wall of the duodenum has Brunner’s glands which secrete mucus and enzymes. Ileum is the ongest part of the small intestine and opens into the caecum of the large intestine.
The ileal mucosa has numerous vascular projections called villi which are involved in the process of absorption and the cells lining the villi produce numerous microscopic projections called microvilli giving a brush border appearance that increase the surface area enormously.
Along with Villi, the ileal mucosa also contain mucus secreting 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.
