internal anal sphincter
Quick Summary
The internal anal sphincter is a ring of smooth muscle tissue that surrounds the anal canal. It is part of the involuntary muscular system that controls the evacuation of feces. This sphincter is located within the anal canal, just above the external anal sphincter, which is under voluntary control. The internal anal sphincter relaxes reflexively when the rectum is distended, initiating the urge to defecate. Its primary function is to maintain the closure of the anal opening, preventing involuntary leakage of waste.1234
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- anal canal
The internal sphincter is part of the inner surface of the canal; it is composed of concentric layers of circular muscle tissue and is not under voluntary control. The external sphincter is a layer of voluntary (striated) muscle encircling the outside wall of the anal canal…
Read MoreThe internal sphincter is part of the inner surface of the canal; it is composed of concentric layers of circular muscle tissue and is not under voluntary control. The external sphincter is a layer of voluntary (striated) muscle encircling the outside wall of the anal canal…
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human digestive systemRectum and anusThus, the internal sphincter is composed of smooth muscle and is innervated by the autonomic nervous system, while the external sphincters are of striated muscle and have somatic (voluntary) innervation provided by nerves called the pudendal nerves.
Read MoreThus, the internal sphincter is composed of smooth muscle and is innervated by the autonomic nervous system, while the external sphincters are of striated muscle and have somatic (voluntary) innervation provided by nerves called the pudendal nerves.
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