PSYC340 Study Guide - Final Guide: Myenteric Plexus, Mesothelium, Adventitia
24 Jun 2018
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1. Describe the structures and functions of the layers that form the wall of the gastrointestinal
tract.
A. Layers of the GI tract
A.I. Mucosa
A.II. The mucosa, or inner lining of the GI tract, is a mucous membrane. It is
composed of (1) a layer of epithelium in direct contact with the contents
of the GI tract, (2) a layer of connective tissue called the lamina propria,
and (3) a thin layer of smooth muscle (muscularis mucosae)
A.III. Epithelium
A.IV. In the mouth, pharynx, esophagus, and anal canal is mainly
nonkeratinized stratified squamous epithelium that serves a protective
function. Simple columnar epithelium, which functions in secretion and
absorption, lines the stomach and intestines. The tight junctions that
firmly seal neighboring simple columnar epithelial cells to one another
restrict leakage between the cells. The rate of renewal of GI tract
epithelial cells is rapid: Every 5 to 7 days they slough off and are replaced
by new cells.
A.V. Enteroendocrine cells
A.VI. Located among the epithelial cells are exocrine cells that secrete mucus
and fluid into the lumen of the tract, and several types of endocrine cells,
collectively called enteroendocrine cells. That secrete hormones
A.VII. Lamina propria
A.VIII. Is areolar connective tissue containing many blood and lymphatic vessels,
which are the routes by which nutrients absorbed into the GI tract reach
the other tissues of the body. This layer supports the epithelium and
binds it to the muscularis mucosae (discussed next
A.IX. Mucosa associated lymphatic tissue (MALT)
A.X. The lamina propria also contains the majority of the cells of the mucosa
associated lymphatic tissue (MALT).
A.XI. MALT is present all along the GI tract, especially in the tonsils, small
intestine, appendix, and large intestine.
A.XII. Muscularis mucosae
A.XIII. A thin layer of smooth muscle fibers called the muscularis mucosae
throws the mucous membrane of the stomach and small intestine into
many small folds, which increase the surface area for digestion and
absorption. Movements
of the muscularis mucosae ensure that all absorptive cells are fully
exposed to the contents of the GI tract.
A.XIV. Submucosa
A.XV. The submucosa consists of areolar connective tissue that binds the
mucosa to the muscularis. It contains many blood and lymphatic vessels
that receive absorbed food molecules. Also located in the submucosa is
an extensive network of neurons known as the submucosal plexus (to be
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Document Summary
Describe the structures and functions of the layers that form the wall of the gastrointestinal tract, layers of the gi tract. The mucosa, or inner lining of the gi tract, is a mucous membrane. It is composed of (1) a layer of epithelium in direct contact with the contents of the gi tract, (2) a layer of connective tissue called the lamina propria, and (3) a thin layer of smooth muscle (muscularis mucosae) In the mouth, pharynx, esophagus, and anal canal is mainly nonkeratinized stratified squamous epithelium that serves a protective function. Simple columnar epithelium, which functions in secretion and absorption, lines the stomach and intestines. The tight junctions that firmly seal neighboring simple columnar epithelial cells to one another restrict leakage between the cells. The rate of renewal of gi tract epithelial cells is rapid: every 5 to 7 days they slough off and are replaced by new cells.
