Sileälihasten

Sileälihasten, also known as smooth muscles, are a type of muscle tissue that is found in the walls of internal organs and structures, such as the digestive tract, uterus, blood vessels, and bladder. Unlike skeletal muscles, which are under voluntary control, smooth muscles are involuntary, meaning they contract and relax without conscious thought. This allows for continuous, automatic functions essential for life.

The cells that make up smooth muscle tissue are spindle-shaped and have a single, central nucleus. They are arranged in sheets or layers, and their contraction is slower and more sustained than that of skeletal muscles. This characteristic enables smooth muscles to perform tasks like propelling food through the digestive system, regulating blood pressure by constricting or dilating blood vessels, and expelling a baby during childbirth.

Smooth muscle contraction is initiated by various stimuli, including hormonal signals, neurotransmitters from the autonomic nervous system, and stretching of the muscle itself. The precise mechanism involves the interaction of actin and myosin filaments, similar to skeletal muscle, but with a different regulatory pathway. The sustained nature of smooth muscle contraction is crucial for maintaining muscle tone and for prolonged functions like emptying organs. Disorders affecting smooth muscle can lead to a range of health issues, from digestive problems to cardiovascular diseases.