Smooth muscle

Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs; such as blood vessels, the bladder, the uterus, and the gastrointestinal tract. Smooth muscle tissue serves to guide medium transport, such as blood, urine, sperm, bile by means of controlled contractions inducing peristaltic movements.

Smooth muscle cells are mediated by the autonomic nervous system ("involuntarily" control), but can also react on stimuli from neighbouring cells and on hormones (vasodilators or vasoconstrictor) within the medium that it carries. Within the cells, calcium ions induce contractions. They are generally arranged in sheets or bundles and connected by gap junctions. In relaxed state, each cell is spindle-shaped, 25-50 um long and 5 um wide.

The mechanism in which external factors stimulate growth and rearrangement is not yet fully understood. The cells are able to produce their own extracellular matrix. When cultured outside the body, the cells tend to differentiate into a synthetic phenotype, which is not able to contract.

See also: skeletal muscle, cardiac muscle, vascular smooth muscle

Related Diseases
"Smooth muscle condition" is a condition in which the body of a developing embryo does not create enough smooth muscle for the gastrointestinal system. This condition is fatal.

Anti-smooth muscle antibodies (ASMA) can be a symptom of an auto-immune disorder, such as hepatitis, cirrhosis, or lupus.