A scientist is studying the mechanism by which the gastrointestinal system coordinates the process of food digestion. Specifically, she is interested in how distension of the lower esophagus by a bolus of food changes responses in the downstream segments of the digestive system. She observes that there is a resulting relaxation and opening of the lower esophageal (cardiac) sphincter after the introduction of a food bolus. She also observes a simultaneous relaxation of the orad stomach during this time. Which of the following substances is most likely involved in the process being observed here?
ANeuropeptide-Y
BSecretin
CGhrelin
DVasoactive intestinal polypeptide
EMotilin
A 50-year-old woman with long-standing diabetes presents with severe, watery diarrhea that wakes her at night. Stool studies show normal osmotic gap and negative stool cultures. Colonoscopy is normal. Trial of fasting does not improve diarrhea. Gastric emptying study shows delayed emptying. What neurotransmitter deficiency in the enteric nervous system best explains both her gastric and colonic dysmotility?
AAcetylcholine
BSerotonin
CNitric oxide
DSubstance P
EVasoactive intestinal peptide
A 25-year-old man undergoes extensive small bowel resection following trauma, leaving 40 cm of jejunum anastomosed to the ascending colon. The ileocecal valve is removed. Six months postoperatively, he requires total parenteral nutrition. Despite this, he develops calcium oxalate kidney stones. Evaluate the mechanism linking his intestinal resection to nephrolithiasis.
ADecreased urinary citrate from chronic metabolic acidosis
BHyperparathyroidism from vitamin D malabsorption causing hypercalciuria
CIncreased colonic absorption of oxalate due to enhanced permeability from bile salts
DDehydration from chronic diarrhea concentrating urinary oxalate
EIncreased enteric oxalate absorption from calcium binding to malabsorbed fatty acids
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