The GI tract from the esophagus to the anal canal is composedof four tunics. Describe the general histology of the tunics andthe specific features of the stomach tunics
The GI tract from the esophagus to the anal canal is composed
of four tunics. Describe the general histology of the tunics and
the specific features of the stomach tunics
The digestive tract is approximately nine meters long continuous tube that is open at both ends. It runs through the mouth to the anus and has the same basic wall structure throughout the entire tube's length. The stomach, small intestine and large intestine are parts of the digestive tract.
Digestive tracts tunics:
- Mucosa- It consists of three sub-layers called the epithelium, lamina propria and the muscularis mucosa. The epithelium is made of simple columnar cells, lamina propria of blood vessels and nerves containing small areolar tissues and muscularis mucosa is made of smooth muscle's thin layers.
- Sub-mucosa- the areolar and dense irregular connective tissue make up the sub0mucosa. It is richly supplied with lymph vessels, blood vessels and nerves. It houses mucosal-associated lymphoid tissue (MALT) to prevent pathogen invasion through the wall.
- Muscularis externa- It consists of an inner circular and an outer longitudinal layer of the smooth muscles. The myenteric plexus lies between the two muscle layers.
- Adventitia- It is the outer layer of the digestive tract that is composed of areolar connective tissue.
The mucosal layer of the stomach contains simple columnar epithelium for absorption, gastric pits and gastric glands (parietal, chief, enteroendocrine cells) for the secretion of HCl and pepsin. The contraction in the muscularis mucosa helps in the expulsion of the gastric glands' contents. Adventitia is called serosa in the stomach and intestinal regions.
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