Microscopic Anatomy of the Digestive Tract

Microscopic Anatomy of the Digestive Tract

All parts of the digestive system, from the esophagus to the rectum, have a similar histological structure and consist of the same three layers: the inner mucosa (or simply “mucosa”), the middle muscular layer and the outer connective tissue layer. The inner lining of the mucous membrane, extending into the lumen of the digestive tract, consists of epithelial cells (usually columnar); some of them secrete a viscous mucus that serves as a lubricant. The mucous membrane of the stomach and intestines forms many folds, which increases the secreting and absorption surface.

The glands of the digestive tract develop from pockets of the mucous membrane. The muscle layer consists of smooth muscle; Only in the upper third of the esophagus is it formed by striated muscles. Most of the digestive tract has two layers of muscle: the inner one, with a circular arrangement of fibers, and the outer one, the fibers of which run in the longitudinal direction.

Alternate or joint contraction of these layers allows the digestive organs to carry out a variety of movements to mix food and push it forward. The outermost layer of the wall of the digestive tract consists of strong flexible connective tissue fibers and is covered with a smooth membrane - the peritoneum. The peritoneum secretes a fluid that lubricates the surface of the stomach and intestines and reduces friction between parts of the digestive tract against each other and against the walls of the abdominal cavity.

The esophagus, which lies among the muscles of the neck and chest, does not have a covering similar to the peritoneum. The walls of the digestive tract are abundantly supplied with nerves that coordinate the work of its different parts, and with blood and lymphatic vessels for delivering food and oxygen to cells, removing metabolic products and transporting absorbed nutrients to places of their storage.