Smooth muscle
Smooth Muscle
Smooth muscle (pronunciation: /smuːð ˈmʌskəl/) is a type of muscle tissue that is non-striated and involuntary. It is one of the three types of muscle found in the human body, the other two being skeletal muscle and cardiac muscle.
Etymology
The term "smooth muscle" is derived from the Latin words 'levis', meaning smooth, and 'musculus', meaning muscle. This is due to the smooth, non-striated appearance of this type of muscle under a microscope.
Function
Smooth muscle is found in the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, blood vessels, and the arrector pili in the skin. Its primary function is to contract and relax to facilitate bodily functions such as digestion, urination, and childbirth.
Structure
Unlike skeletal and cardiac muscle, smooth muscle is not striated. Its cells are spindle-shaped, with a single nucleus in the center. The cells are arranged in sheets, with the actin and myosin filaments crisscrossing the cell, allowing for contraction.
Related Terms
- Actin: A protein that forms the contractile filaments of muscle cells.
- Myosin: A type of motor protein that is involved in muscle contraction.
- Arrector Pili: Small muscles attached to hair follicles in mammals. Contraction of these muscles causes the hairs to stand on end, known colloquially as goosebumps.
- Peristalsis: The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward.
External links
- Medical encyclopedia article on Smooth muscle
- Wikipedia's article - Smooth muscle
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