Sphincter muscles
Sphincter Muscles
The Sphincter Muscles (/sfɪŋktər/; from Greek: σφίγγω, sphíngō, "to squeeze") are a group of muscles that have the ability to close off a bodily opening or passage. They are typically circular muscles that maintain constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning.
Etymology
The term "sphincter" is derived from the Greek word "sphincter," which means "band" or "girdle." It was first used in the English language in the late 16th century.
Types of Sphincter Muscles
There are over 60 types of sphincter muscles in the human body. Some of the most well-known include:
- Anal Sphincter: This muscle surrounds the anus and helps control the expulsion of feces from the body.
- Urethral Sphincter: This muscle surrounds the urethra and controls the release of urine from the body.
- Pyloric Sphincter: This muscle is located at the lower end of the stomach and controls the passage of food into the small intestine.
- Lower Esophageal Sphincter: This muscle is located at the junction of the esophagus and the stomach and prevents the backflow of stomach acid into the esophagus.
Related Terms
- Muscle Contraction: The process by which muscles become shorter and tighter, causing movement.
- Orifice: An opening, as of a pipe or tube, or one leading out of the body.
- Physiology: The branch of biology that deals with the normal functions of living organisms and their parts.
External links
- Medical encyclopedia article on Sphincter muscles
- Wikipedia's article - Sphincter muscles
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