Sileänlihaskudoksen

Sileänlihaskudoksen, also known as smooth muscle tissue, is a type of muscle tissue that is found in the walls of hollow organs in the body. Unlike skeletal muscle, which is under voluntary control, smooth muscle is involuntary, meaning its contractions are not consciously controlled. This type of muscle is responsible for a variety of bodily functions, including the movement of food through the digestive tract (peristalsis), regulating blood flow by altering the diameter of blood vessels, and expelling urine from the bladder.

The cells that make up smooth muscle tissue are elongated and spindle-shaped, with a single, centrally located nucleus. They are arranged in sheets or layers within the organ walls, and their contractions can be slow and sustained or rapid and rhythmic, depending on the specific location and function. This tissue is innervated by the autonomic nervous system, which regulates its activity based on the body's internal needs. Hormones can also influence smooth muscle contraction.

Examples of organs containing significant amounts of smooth muscle include the stomach, intestines, uterus, bladder, blood vessels, and the iris of the eye. Its ability to contract and relax without conscious effort is crucial for maintaining homeostasis and ensuring the proper functioning of many vital organ systems. The structure and function of smooth muscle are distinct from those of cardiac muscle (found in the heart) and skeletal muscle.