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Smooth muscle is found in the wall of hollow organs, passageways, tracts, eye and skin. Structure. Fibers of smooth muscle group in branching bundles, which allows for cells to contract much stronger than those of striated musculature. Functions. Smooth muscle has different functions in the Human body, including: Sealing orifices;
Smooth muscle can be stimulated by pacesetter cells, by the autonomic nervous system, by hormones, spontaneously, or by stretching. The fibers in some smooth muscle have latch-bridges, cross-bridges that cycle slowly without the need for ATP; these muscles can maintain low-level contractions for long periods.
Smooth muscle is composed of sheets or strands of smooth muscle cells. These cells have fibers of actin and myosin which run through the cell and are supported by a framework of other proteins. Smooth muscle contracts under certain stimuli as ATP is freed for use by the myosin.
Gross anatomy. The dense bodies and intermediate filaments are networked through the sarcoplasm, which cause the muscle fiber to contract. Smooth muscle is grouped into two types: single-unit smooth muscle, also known as visceral smooth muscle, and multiunit smooth muscle.
Smooth muscle differs from skeletal muscle in function. Unlike skeletal muscle, smooth muscle is capable of maintaining tone for extended periods and often contracts involuntarily. At a cellular level, smooth muscle can be described as an involuntary, non-striated muscle.
Smooth muscle fibers are spindle-shaped (wide in the middle and tapered at both ends, somewhat like a football) and have a single nucleus; they range from about 30 to 200 μ m (thousands of times shorter than skeletal muscle fibers), and they produce their own connective tissue, endomysium.
The primary function of smooth muscle is contraction. Smooth muscle consists of two types: single-unit and multi-unit. Single-unit smooth muscle consists of multiple cells connected through connexins that can become stimulated in a synchronous pattern from only one synaptic input.