Answer
The layers of tissues common to most of the digestive tract are--the mucosa, the submucosa, the muscularis externa, and the serosa.
Work Step by Step
The mucosa:
This is the inner epithelial lining of the digestive tract tube. It comprises an innermost layer of columnar epithelial cells over a lamina propria of loose connective tissue. External to the lamina propria is a layer of smooth muscle called the muscularis mucosae. The epithelial lining is mostly simple columnar epithelium, except from mouth cavity to esophagus, and in the distal anal canal where it becomes stratified squamous epithelium (nonkeratinized) which is more resistant to abrasive action.
The muscularis mucosae is a thin layer of smooth muscle which is really part of the mucasa.
Contractions of the muscularis mucosa create groves and ridges over the mucosal surface,
increasing surface area and the efficiency of digestion and absorption of nutrients.
The mucosa also has many lymphocytes and lymphatic nodules--MALT also contains
The submucosa is a thick loose highly vascular layer of connective tissue, which also contains nerve plexuses and lymphatic vessels. It may also contain glands that secrete lubricating mucus into the lumen/ cavity of the digestive tract
The muscularis externa comprises two layers of smooth muscle:
a. The inner layer: Cells of the inner layer go around the tract and form regulatory sphincters
that control the movement of materials through the tract.
b. The outer, more superficial layer consists of longitudinal fibers. Longitudinal fibers play an
important role in digestive tract motility and in the propulsion of substances through the
alimentary canal.
The serosa. The serosa comprises an upper layer of squamous epithelium (mesothelium) upon a thin layer of areolar connective tissue. This layer begins in the lower esophagus and continues through the alimentary canal to terminate close to the beginning of the rectum.
In the pharynx, most of the esophagus and the rectum the serosa is replaced by a fibrous connective tissue layer called the adventitia.
