Describe the histology of alimentary canal

The wall of alimentary canal from oesophagus to rectum possesses four layers

namely serosa, muscularis, sub-mucosa and mucosa.

- Serosa is the outermost layer and is made up of a thin mesothelium (epithelium of

visceral organs) with some connective tissues.

- Inner to serosa is the layr called muscularis, which is formed by smooth muscles

usually arranged into an inner circular and an outer longitudinal layer.

- Submucosal layer is the third layer, formed of loose connective tissues containing

nerves, blood and lymph vessels; glands are present in the submucosal layer of

duodenum.

- Mucosa is the innermost layer lining the lumen of the alimentary canal. This

layer forms irregular folds (rugae) in the stomach and small finger-like foldings

called villi in the small intestine

- The cells lining the villi produce numerous microscopic projections called

microvilli giving a brush border appearance. These modifications increase the

surface area enormously.

- Villi are supplied with a network of capillaries and a large lymph vessel called the

lacteal.

- Mucosal epithelium has goblet cells and crypts of Lieberkuhn in between the

bases of villi in the intestine.