What is the role of the small intestine's MALT?

Correct Answer: D

Rationale: The role of the small intestine's MALT (Mucosa-Associated Lymphoid Tissue) is to prevent bacteria from entering the bloodstream. MALT contains immune cells that help protect the body from harmful pathogens in the gut. When bacteria breach the intestinal barrier, MALT responds by generating an immune response to eliminate the invaders and prevent systemic infection. This function is crucial for maintaining the body's overall health and preventing infections. Choice A (secreting mucus) is incorrect because mucus secretion is primarily performed by goblet cells in the intestine to lubricate and protect the intestinal lining, not by MALT. Choice B (buffering acidic chyme) is incorrect as buffering acidic chyme is mainly done by bicarbonate secreted by the pancreas to neutralize stomach acid, not by MALT. Choice C (activating pepsin) is incorrect as pepsin activation occurs in the stomach, not in the small intestine's MALT.

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: C

Rationale: The correct answer is C: digestive enzymes. The pancreas secretes digestive enzymes such as amylase, lipase, and protease to aid in the digestion of carbohydrates, fats, and proteins in the small intestine. These enzymes break down food molecules into smaller nutrients that can be absorbed by the body. Bile (choice A) is produced by the liver and stored in the gallbladder, not the pancreas. Gastric acid (choice B) is produced by the stomach to aid in the digestion of proteins. Insulin (choice D) is a hormone produced by the pancreas that regulates blood sugar levels, not aid in digestion.

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.