Sileälihakselta

Sileälihakselta is a Finnish term referring to smooth muscle tissue. Smooth muscle is one of the three types of muscle tissue in the body, the other two being skeletal muscle and cardiac muscle. Unlike skeletal muscle, which is under voluntary control, smooth muscle is involuntary, meaning it contracts and relaxes without conscious effort. This type of muscle is found in the walls of internal organs and structures, such as the digestive tract, blood vessels, uterus, and bladder.

The cells that make up smooth muscle are spindle-shaped and have a single, centrally located nucleus. They are arranged in sheets or layers within the organ walls. Contraction of smooth muscle is generally slower and more sustained than that of skeletal muscle. This allows for functions such as propelling food through the digestive system (peristalsis), regulating blood flow by constricting or dilating blood vessels, and expelling urine from the bladder.

The regulation of smooth muscle contraction is complex and involves various factors, including hormones, neurotransmitters, and local stimuli. For instance, hormones like adrenaline can affect the contraction of smooth muscle in blood vessels, influencing blood pressure. Neurotransmitters released from the autonomic nervous system also play a crucial role in controlling the activity of smooth muscle in many organs. Damage or dysfunction of smooth muscle can lead to various health issues, depending on the affected organ system.