Internal anal sphincter
Internal Anal Sphincter
The Internal Anal Sphincter (pronunciation: /ɪnˈtɜːrnl ˈeɪnəl ˈsfɪŋktər/) is a muscular ring that surrounds about 2.5-4 cm of the anal canal; its job is to keep the anus closed and prevent unwanted leakage of fecal matter.
Etymology
The term "Internal Anal Sphincter" is derived from the Latin words "internus" meaning inside, "anus" meaning ring, and "sphincter" meaning tight band.
Anatomy
The Internal Anal Sphincter is an involuntary muscle, which means it contracts without conscious control. It is a continuation of the circular muscle layer of the rectum. It is thicker than the external anal sphincter, which is a voluntary muscle that surrounds the internal sphincter and the anal canal.
Function
The primary function of the Internal Anal Sphincter is to prevent leakage of gas and fecal matter at rest and during periods of increased intra-abdominal pressure. It maintains about 85% of resting anal pressure and its relaxation allows for defecation.
Related Terms
- Anus: The opening at the end of the digestive tract where bowel contents leave the body.
- Rectum: The final section of the large intestine, terminating at the anus.
- Defecation: The discharge of feces from the body.
- Sphincter: A ring of muscle surrounding and serving to guard or close an opening or tube, such as the anus or the openings of the stomach.
See Also
External links
- Medical encyclopedia article on Internal anal sphincter
- Wikipedia's article - Internal anal sphincter
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