Humans normally have 20 deciduous or 'baby' teeth and adults 32 permanent teeth. The 12 additional teeth in humans represent

Correct Answer: C

Rationale: The correct answer is C: premolars and molars. Deciduous teeth consist of incisors, canines, and molars, totaling 20 in children. Adults have 32 permanent teeth, which include incisors, canines, premolars, and molars. Therefore, the 12 additional teeth in adults are the premolars and molars, making choice C the correct answer. Choice A (incisors and canines) is incorrect because these teeth are present in both deciduous and permanent dentition. Choice B (canines and premolars) is incorrect as it does not account for all 12 additional teeth in adults. Choice D (all molars) is incorrect as it excludes the premolars, which are also part of the additional teeth in adults.

Correct Answer: A

Rationale: The correct answer is A: plicae circulares; increase surface area. Plicae circulares are circular folds in the small intestine that increase surface area for nutrient absorption. They help in maximizing contact with digested food. Villi and microvilli are structures on the surface of the small intestine that further increase surface area for absorption but are not the folds themselves. Rugae are folds found in the stomach, not the small intestine.

Correct Answer: C

Rationale: The correct answer is C: bicarbonate ions. Pancreatic juice is alkaline to neutralize the acidic chyme entering the small intestine from the stomach. Bicarbonate ions are secreted by pancreatic duct cells and play a major role in maintaining the pH balance. Mucus (choice A) is produced by goblet cells and helps protect the lining of the digestive tract but is not a major component of pancreatic juice. Trypsinogen, chymotrypsinogen, and procarboxypeptidase (choice B) are pancreatic enzymes, not the major component of the aqueous component. Secretin (choice D) is a hormone that stimulates the pancreas to release bicarbonate ions but is not a component of pancreatic juice itself.

Correct Answer: A

Rationale: The correct answer is A: chylomicron. After absorption, free fatty acids and glycerol are recombined in the epithelial cell to form triglycerides. These triglycerides are then packaged with proteins to form chylomicrons, which are lipoprotein particles that transport dietary fats through the lymphatic system and bloodstream. Chylomicrons are essential for the absorption of dietary fats and fat-soluble vitamins. Summary: - B: Micelle is incorrect because micelles are formed in the lumen of the small intestine to aid in the absorption of lipids but do not involve recombination of fatty acids and glycerol. - C: Lipoprotein is incorrect because while chylomicrons are a type of lipoprotein, the specific process described in the question is not about general lipoprotein formation. - D: Fatty droplet is incorrect as it does not involve the recombination and protein coating process described in the question.

Correct Answer: B

Rationale: The correct answer is B because the colonic microbiota performs multiple essential functions such as aiding in digestion, producing vitamins, regulating immune function, and maintaining gut barrier integrity. Option A is incorrect as it focuses on dietary fiber intake rather than the microbiota's functions. Option C is incorrect because while acetate, propionate, and butyrate are important organic acids produced, they are not the only ones. Option D is incorrect as the microbiota's establishment of an 'acetate buffer' does not necessarily suppress the growth of all pathogenic bacteria.