Sileälihassolujen

Sileälihassolut, also known as smooth muscle cells, are a type of muscle cell found in the walls of internal organs and structures in the body. Unlike skeletal muscle cells, which are under voluntary control, or cardiac muscle cells, which are found only in the heart, smooth muscle cells are involuntary. This means their contraction and relaxation are regulated by the autonomic nervous system, hormones, and local factors, rather than conscious thought.

These cells are spindle-shaped and have a single, centrally located nucleus. Their cytoplasm is filled with actin and myosin filaments, similar to other muscle types, but these filaments are arranged differently, giving smooth muscle its characteristic lack of striations. This arrangement allows smooth muscle to contract and relax more slowly and sustain contractions for longer periods than skeletal muscle.

Smooth muscle plays a crucial role in a variety of bodily functions. It is found in the walls of blood vessels, where it regulates blood pressure and flow by constricting or dilating the vessels. In the digestive tract, smooth muscle contractions propel food along the intestines through a process called peristalsis. It is also present in the airways, the bladder, the uterus, and the iris of the eye, contributing to their respective functions. The coordinated action of smooth muscle cells allows for essential internal processes to occur continuously and efficiently without conscious effort.