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Gianni Bornales Napatutan posted an update in the group
Medical Histology Art – MT 30 Lab C (2022) 3 years, 10 months ago Certain structural characteristics are shared by all sections of the GI tract. The GI tract is a hollow tube with a variable-diameter lumen and a wall composed of four major layers: the mucosa, submucosa, muscular, and serosa.
The mucosa is made up of an epithelial lining, an underlying lamina propria of loose connective tissue rich in blood vessels, lymphatics, lymphocytes, smooth muscle cells, and often small glands, and a thin layer of smooth muscle called the muscularis mucosae that separate the mucosa from the submucosa and allows local mucosa movements. The mucosa is also known as the mucous membrane.
The submucosa has denser connective tissue, bigger blood and lymph arteries, and the Meissner plexus of autonomic nerves. It may also contain glands and lymphoid tissue in substantial amounts.
Smooth muscle cells are grouped as two or more sublayers in the thick muscular (or muscularis externa).
The fiber orientation in the internal sublayer (closer to the lumen) is often circular; in the external sublayer, it is longitudinal. Blood and lymph arteries, as well as the myenteric (Auerbach) nerve plexus of numerous autonomic neurons aggregated into tiny ganglia and being interconnected by pre- and postganglionic nerve fibers, are found in the connective tissue between the muscle sublayers. The enteric neural system of the digestive tract is made up of this and the submucosal plexus. The myenteric plexus generates and coordinates muscularis contractions, which mix and move luminal contents forward.
The serosa is the outermost layer of the digestive tract located within the abdominal cavity. It is a thin sheet of loose connective tissue rich in blood arteries, lymphatics, and adipose tissue and covered by a basic squamous covering epithelium or mesothelium. The small and large intestine serosa both are continuous with sections of the mesentery, a vast fold of adipose connective tissue covered on both sides by mesothelium that suspends the intestines, and is continuous with the peritoneum, the serous membrane covering the abdominal cavity. The esophagus is not hanging in a hollow but is physically connected to neighboring structures.
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