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Smooth muscle-containing tissue needs to be stretched often, so elasticity is an important attribute of smooth muscle. Smooth muscle cells may secrete a complex extracellular matrix containing collagen (predominantly types I and III), elastin, glycoproteins, and proteoglycans. Smooth muscle also has specific elastin and collagen receptors to ...
The muscularis mucosae (or lamina muscularis mucosae) is a thin layer of muscle of the gastrointestinal tract, located outside the lamina propria, and separating it from the submucosa. It is present in a continuous fashion from the esophagus to the upper rectum (the exact nomenclature of the rectum's muscle layers is still being debated).
The muscle fiber cells are arranged in 5 to 7 layers of circular and longitudinal smooth muscle with about 50μ in length and contain well-marked, rod-shaped nuclei, which are often slightly curved. Separating the tunica media from the outer tunica externa in larger arteries is the external elastic membrane (also called the external elastic ...
Smooth muscle tissue is non-striated and involuntary. Smooth muscle is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin that control the erection of body hair.
In the upper esophagus, part of the externa is skeletal muscle, rather than smooth muscle. In the vas deferens of the spermatic cord, there are three layers: inner longitudinal, middle circular, and outer longitudinal. In the ureter, the smooth muscle orientation is opposite that of the GI tract. There is an inner longitudinal and an outer ...
The endoderm produces tissue within the lungs, thyroid, and pancreas. The mesoderm aids in the production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells. The ectoderm produces tissues within the epidermis and aids in the formation of neurons within the brain, and melanocytes.
Smooth muscle tissue, for example, is hard to differentiate from collagen. A trichrome stain can colour the muscle tissue red, and the collagen fibres green or blue. Liver biopsies may have fine collagen fibres between the liver cells, and the amount of collagen may be estimated based on the staining method.
These are detected in the lamina propria of the seminiferous tubule and immunohistochemical studies have shown functional distinctions between these layers. The inner layers have been shown to express desmin, a smooth muscle phenotype, whereas the outer layers express vimentin, a connective tissue phenotype. [2]