Describe the basic histological (tissue) structure of the mucosa layer in the alimentary canal. Identify the unique features of the mucosa in the stomach and the duodenum, and explain how this uniqueness determines the function of the stomach and the duodenum.

The basic tissue structure of the mucosa layer of the alimentary canal consists of:

--> mucous membrane

--> lamina propria

--> muscularis mucosa

Explanation:

The MUCOUS MEMBRANE forms the innermost layer of the alimentary canals which includes the stomach and the duodenum (small intestine) . It's major functions is protection, secretions and absorption. The type of mucous membrane found in the stomach and duodenum is the Columnar epithelial cells. Not numerous gastric glands are situated below the surface in the mucous membrane of the stomach. They consist of specialised cells that secrete gastric juice that aids in the digestion of food. While the duodenal mucosa consists of mucous producing goblet cells. These cells produce a viscous, alkaline mucus that protects against the acidic gastric juices and pepsin. The folding of these mucosal cells (microvilli) provides a large surface area to optimize nutrient absorption.

The LAMINA PROPRIA: This layer separates the mucous membrane and the muscularis mucosa. It is made up of connective tissues which supports the blood vessels that nourishes the inner epithelial layer. In both the stomach and duodenum, digested nutrients are absorbed into the capillaries.

MUSCULARIS MUCOSA: This is made up of thin layer of smooth involuntary muscles. The contraction and relaxation of these muscle layers occurs in waves, which push the contents of the tract onwards. This type of contraction is called peristalsis which occurs in the duodenum. While in the stomach, these muscles allows for the churning motion characteristic of gastric activities.