Question

4 layers of alimentary canal

Answer 1

there are 4 levels of alimentary canal.....
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Answer 2

Four Layers of Alimentary Canal:

Wall of alimentary canal from oesophagus to rectum consists of four layers- serosa, muscularis, sub–mucosa and mucosa.

Serosa is the outermost layer made up of thin mesothelium (squamous epithelium of visceral organs).

Muscularis consists of smooth muscles arranged in inner circular and outer longitudinal layer. Oblique muscle forms the inner most layer in stomach region only. Muscularis is responsible for peristalsis and mixing of food with digestive juices.

Sub-mucosa consists of areolar connective tissue containing nerve, blood and lymph vessels.

Note: In duodenum only, glands are also present in sub-mucosa. These glands secrete alkaline fluid to neutralize acidity of chyme coming from stomach.

Mucosa:

· It is the inner most layer made up of simple columnar epithelium.

· It forms irregular folds called rugae in an empty stomach.

· It also forms small finger like folding called villi in small intestine.

· Villi are supplied with a network of capillaries and large lymphatic vessels called lacteals.

· Mucosa of intestine forms Crypts of Leiberkuhn in between the bases of villi which secrete intestinal juice.

· Villi produce numerous microscopic projections called microvilli giving a brush border appearance.

· This modification increases the surface area of small intestine enormously for efficient absorption of digested food.

Two networks of nerves in the wall of alimentary canal are:

· Meissner’s plexus in sub-mucosa which regulates secretion of digestive juices in various regions of gut.

· Aurbach’s plexus in Muscularis which controls peristalsis.

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