ABDOMINAL
GASTROINTESTINAL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Reflected contractions of his muscles and the desire to defecate.
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The desire to defecate.
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parasympathetic innervation
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None of the above
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Detailed explanation-1: -Rectal distension from stool or gas induces reflex relaxation of the internal anal sphincter, known as the rectoanal inhibitory reflex (RAIR). The RAIR is mediated through the enteric nervous system and does not require any external control from the peripheral or central nervous system.
Detailed explanation-2: -The defecation reflex is triggered when: The muscles in the colon contract to move stool toward the rectum. This is known as a “mass movement.” When enough stool moves to the rectum, the amount of stool causes the tissues in the rectum to stretch or distend.
Detailed explanation-3: -The external sphincter muscle is a “voluntary” muscle; you have control over this muscle. It assists in keeping the stool in the rectum until you are ready to have a bowel movement. In fact, squeezing the external sphincter muscle pushes the stool out of the anal canal (5) and the rectum relaxes.
Detailed explanation-4: -This reflex, called the rectosphincteric reflex, also stimulates the external anal sphincter to contract, leading to the urge to defecate.