The Human Gut: Generalized Structure

The gut though consisting of different regions with special characteristics, they all have a common structure and these can be classified into four distinct layers:

1. The Muscularis externa
2. The Serosa
3. The Mucosa
4. And the Submucosa

Muscularis Externa
The Muscularis externa is composed of an involuntary muscle known as the smooth muscle and has two layers (inner circular and outer longitudinal layer). These layers are what cause blood to move along the gut and also mixes the food as it moves along. It also controls the movement of food using the circular muscle, when this muscle thickens it forms structures known as sphincters.
Serosa
This is composed of loose fibrous connective tissue. It is located in the outermost part of the gut wall. This tissue forms what is known as Mesenteries which support the stomach and intestines from the body wall. Mesenteries consists of double layers of peritoneum (these cover most of the outer surface of the gut). It is usual for gut walls to slide over other organs or even portions of itself, so what peritoneum does is that it helps to reduce the friction on the gut when it slides over these organs or itself.
Mucosa
This forms the innermost layer of the gut and it has three  layers:

1. Epithelium
2. lamina Propria
3. And Muscularis mucosa

Epithelium:- This has a number of functions namely the secretion of mucus for lubricating food and  preventing the digestion of the walls of the gut by its own enzymes.
Lamina Propria:- Contains glands formed from the infoldings of epithelium, also contains supporting layer of connective tissue through which blood runs.
Muscularis mucosa:-  Helps in the production of mucosa and Submucosa.
Submucosa
Basically the Submucosa is a layer of connective tissues, Collagen, nerves, lymph vessels and elastic fibres. In the duodenum it deposits its contents from mucus secreting glands onto the surface using ducts.

Read other articles:

The different states of matter