Peristalsis relies on the synchronized contraction and relaxation of______________?
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Answer: A. Above and below the food bolus
Explanation
Peristalsis requires coordinated contraction of circular muscle above the food bolus and relaxation below it. This synchronized enteric reflex propels digestive contents smoothly in an aboral direction through the GI tract. Sequential circular muscle contractions above and downstream relaxation ensure unidirectional movement of food material. Peristalsis is an involuntary wave-like muscle contraction controlled by the enteric nervous system. Myenteric plexus networks coordinate local smooth muscle activity to achieve efficient gastrointestinal motility. Neurotransmitters like serotonin and vasoactive intestinal peptide mediate the localized contraction and relaxation responses.
Gastroenterologists study motility disorders such as gastroparesis and intestinal pseudo-obstruction to diagnose transit issues. Postoperative ileus temporarily halts peristalsis following abdominal surgery, requiring careful patient nutritional management. Understanding digestive tract motility helps pharmacologists develop prokinetic drugs to stimulate bowel movement. Contraction lateral to the bolus does not propel contents forward along the longitudinal axis of the gut. Dorsal and ventral muscle arrangements do not describe the circular and longitudinal layers responsible for gut motility. Since a correct physiological mechanism is provided among the choices, selecting none of the above is wrong.
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