How is the small intestine adapted for nutrient absorption?
CCK is released from the duodenum to promote liver and pancreatic secretion.
Large surface area due to the presence of the plicae circulares, villi, and microvilli.
Acid secretions from the stomach are neutralized in the duodenum.
The small intestine has haustra and rugae both help in nutrient absorption.
The Correct Answer is B
A. CCK is released from the duodenum to promote liver and pancreatic secretion.: CCK (cholecystokinin) is released by duodenal/jejunal enteroendocrine cells and stimulates pancreatic enzyme secretion and gallbladder contraction -this supports digestion but describes a hormonal control mechanism rather than a structural adaptation of the small intestine itself.
B. Large surface area due to the presence of the plicae circulares, villi, and microvilli.: The small intestine’s mucosal folds (plicae circulares), finger-like villi, and microscopic microvilli (brush border) massively increase surface area for absorption.
C. Acid secretions from the stomach are neutralized in the duodenum.: The duodenum receives bicarbonate-rich pancreatic secretions and bile which neutralize gastric acid to create an optimal pH for intestinal enzymes -this is an important functional adaptation that facilitates digestion/absorption but is secondary to the structural surface-area adaptations.
D. The small intestine has haustra and rugae both help in nutrient absorption.: Haustra are sacculations of the large intestine (colon) and rugae are folds in the stomach -neither are features of the small intestine, so this statement is incorrect.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Glomerulus:The glomerulus is the filtration site; ADH/aldosterone act downstream on tubular epithelial cells, not on glomerular filtration directly.
B. Loop of Henle: The loop establishes the medullary gradient; ADH/aldosterone have limited direct action here (ADH affects water permeability mainly in collecting ducts; aldosterone acts mainly on DCT/collecting duct).
C. Vasa recta:Vasa recta are blood vessels that help preserve the medullary gradient (countercurrent exchange) but are not the primary hormone-target epithelial segments for ADH/aldosterone.
D. DCT and collecting duct:Aldosterone acts on the distal convoluted tubule and cortical collecting duct to increase Na⁺ reabsorption (and K⁺ secretion); ADH acts on the late DCT and collecting duct to increase water reabsorption by inserting aquaporins -together they adjust water and sodium retention.
Correct Answer is B
Explanation
A. Muscularis externa, submucosa, mucosa, serosa: This is out of order -muscularis externa is deeper than serosa but more superficial than the mucosa, so this ordering is incorrect.
B. Mucosa, submucosa, muscularis externa, serosa: The mucosa (deepest layer lining the lumen) → submucosa → muscularis externa → serosa (outermost)is the correct sequence from deep to superficial .
C. Serosa, muscularis externa, submucosa, mucosa: This lists the layers from superficial to deep (reverse of what the question asked), so incorrect for deep to superficial.
D. Submucosa, mucosa, muscularis externa, serosa: This places submucosa deeper than mucosa (wrong); incorrect order.
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