What is the function of the intestinal villi?

Correct Answer: B

Rationale: The correct answer is B: absorbing nutrients. Intestinal villi are finger-like projections in the small intestine that increase surface area for absorption of nutrients. They contain specialized cells that absorb nutrients like vitamins, minerals, and digested food particles. Villi do not produce bile (A), secrete enzymes (C), or break down proteins (D). Bile is produced by the liver, enzymes are secreted by the pancreas, and protein breakdown primarily occurs in the stomach.

Correct Answer: B

Rationale: The function of the villi in the small intestine is to absorb nutrients. Villi increase surface area for absorption. They contain blood vessels and lacteals that absorb digested nutrients. Villi do not produce digestive enzymes (A), bile (C), or store glycogen (D). Digestive enzymes are produced by the pancreas and bile by the liver. Glycogen is stored in the liver and muscles.

Correct Answer: D

Rationale: The correct answer is D: Contraction of pancreatic acini. Cholecystokinin (CCK) is a hormone that is released in response to the presence of food in the small intestine. It stimulates the contraction of the smooth muscle in the walls of the pancreatic acini, leading to the release of digestive enzymes into the small intestine to aid in digestion. This action is crucial for the proper breakdown of food molecules. Options A, B, and C are incorrect because CCK does not have a direct effect on oesophageal motility, the sphincter of Oddi, or bile synthesis.

Correct Answer: D

Rationale: The correct answer is D because micelles are indeed clusters of cholesterol, fatty acids, bile salts, and 2 mono-glycerides formed in the small intestine during lipid digestion. This process aids in the absorption of lipids by increasing their surface area for enzymatic action. Choice A is incorrect as emulsified fat globules are not micelles, but rather the initial step in lipid digestion. Choice B is incorrect as pro-enzymes are not related to micelles. Choice C is incorrect as dead enterocytes are not involved in micelle formation.

Correct Answer: D

Rationale: The correct answer is D because iron absorption is regulated to meet the body's needs. When body stores are low or erythropoiesis is increased, absorption increases. This process occurs mainly in the duodenum and upper jejunum, not the terminal ileum as stated in option C. Option A is incorrect because HCl aids in converting iron into a more absorbable form but does not determine the percentage absorbed. Option B is incorrect as the majority of iron absorption occurs in the duodenum and upper jejunum, not the small intestine in general.