Question

What are the four layers of the Gastrointestinal Tract and the function of each?

Answer 1

The four layers of the digestive tract are:

1. Serosa:

It is the outermost single layer of flat cells.

Function: It protects the inner layer.

2. Muscularis:

It is made up of thick, non-striated muscle fibres arranged into three layers forming the  outer layer of longitudinal muscle, middle layer of circular muscles and inner layer of  oblique muscles.

Function: Churns food.

3. Sub-mucosa:

It consists of connective tissue containing blood vessels, nerve fibres and lymphatic vessels.

Function: Absorption

4. Muscular mucosa:

Thin layer of non-striated muscle fibres.

Answer 2

There are a total of four layers - namely, Serosa, Muscularis, Sub-Mucosa and Mucosa.

Serosa:
it is the outermost layer which acts a protection for the inner layers.

Muscularis:
it is further divided into
1) Outer Longitudinal layer - elongated muscles which help in peristalsis in oesophagus
2) Inner circular layer - circular muscles which help in churning of food

Sub-Mucosa:
it is made up of squamous epithelium and contains nerves, blood and lymph vessels.

Mucosa:
it is the layer lining the lumen. it is modified in different parts of the alimentary canal to perform different functions for eg, it is modified to form rugae in the stomach and villi in the small intestine.

Hope it helped :)