The internal anal sphincter is an involuntary smooth muscle that plays a crucial role in maintaining continence by providing a constant baseline tone to the anal canal. It is controlled by the autonomic nervous system and relaxes reflexively in response to rectal distension to allow the passage of stool.

Internal Anal Sphincter

internal anal sphincter

involuntary smooth muscle

maintaining continence

constant baseline tone

The anal canal is the terminal part of the large intestine, extending from the rectum to the anus, and plays a crucial role in the regulation of fecal continence and defecation. It is lined by specialized tissue and muscles, including the internal and external anal sphincters, which coordinate to control the passage of stool.

anal canal

The autonomic nervous system (ANS) is a critical component of the peripheral nervous system responsible for regulating involuntary physiological functions, including heart rate, digestion, respiratory rate, and reflexes. It operates through two main divisions, the sympathetic and parasympathetic nervous systems, which work in tandem to maintain homeostasis and respond to stressors.

autonomic nervous system

Rectal distension refers to the expansion of the rectum due to the accumulation of gas, stool, or other substances, often causing discomfort or pain. It can be a symptom of underlying conditions such as constipation, bowel obstruction, or irritable bowel syndrome, and may require medical evaluation to determine the cause and appropriate treatment.

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