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Smooth muscle is grouped into two types: single-unit smooth muscle, also known as visceral smooth muscle, and multiunit smooth muscle. Most smooth muscle is of the single-unit type, and is found in the walls of most internal organs (viscera); and lines blood vessels (except large elastic arteries), the urinary tract , and the digestive tract .
The muscle of the inner layer is arranged in circular rings around the tract, whereas the muscle of the outer layer is arranged longitudinally. The stomach has an extra layer, an inner oblique muscular layer. [1] Between the two muscle layers is the myenteric plexus (Auerbach's plexus). This controls peristalsis.
In humans, it is about one mm thick, and its surface is smooth, soft, and velvety. It consists of simple secretory columnar epithelium, an underlying supportive layer of loose connective tissue called the lamina propria, and the muscularis mucosae, a thin layer of muscle that separates the mucosa from the underlying submucosa.
Stomach contains an additional oblique muscle layer just interior to circular muscle layer. 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.
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).
Gastroparesis is a condition that happens when your stomach muscles fail to contract normally, which can slow down or stop digestion altogether. This sort of gut paralysis is what leads to ...
Skeletal muscle, is a type of striated muscle, composed of muscle cells, called muscle fibers, which are in turn composed of myofibrils. Myofibrils are composed of sarcomeres, the basic building blocks of striated muscle tissue. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere.
The majority of this type of muscle tissue is found in the digestive and urinary systems where it acts by propelling forward food, chyme, and feces in the former and urine in the latter. Other places smooth muscle can be found are within the uterus, where it helps facilitate birth, and the eye, where the pupillary sphincter controls pupil size. [3]