Which one of the following is most easily absorbed in the oral cavity?

Correct Answer: B

Rationale: The correct answer is B: water. Water is the most easily absorbed in the oral cavity due to its small molecular size and simple structure, allowing for rapid absorption through the mucous membranes in the mouth. Glucose, fatty acids, and peptides are larger molecules that require further breakdown by enzymes in the digestive system before absorption can occur, making them less easily absorbed in the oral cavity. Water, being a small molecule and essential for various physiological functions, can be quickly absorbed directly through the oral mucosa into the bloodstream, providing immediate hydration and other benefits.

Correct Answer: D

Rationale: The correct answer is D because villi are fingerlike projections in the small intestine that increase the surface area for nutrient absorption. Villi have microvilli on their surface, further increasing the absorption area. Option A is incorrect because villi do not secrete mucus; goblet cells in the intestine do. Option B is incorrect because rugae are folds in the stomach lining, not in the small intestine. Option C is incorrect because Crypts of Lieberkuhn are intestinal glands that produce substances, but they are not fingerlike projections like villi.

Correct Answer: B

Rationale: The correct answer is B because the pancreatic islets, also known as the islets of Langerhans, are responsible for producing hormones such as insulin, glucagon, and somatostatin. Insulin helps lower blood sugar levels, glucagon raises blood sugar levels, and somatostatin regulates the release of both insulin and glucagon. The other choices are incorrect because mucus is produced by goblet cells in the intestines, enterokinase is produced by the duodenum to activate pancreatic enzymes, and digestive enzymes are produced by the exocrine cells in the pancreas, not the pancreatic islets.

Correct Answer: C

Rationale: The correct answer is C: pancreas. The pancreas is the main source of lipase production in the body. Lipase is an enzyme responsible for breaking down fats into fatty acids and glycerol. The pancreas secretes pancreatic lipase into the small intestine where it aids in the digestion of fats. Salivary glands produce amylase for carbohydrate digestion, the stomach produces gastric lipase for limited fat digestion, and the small intestine produces additional digestive enzymes but not the majority of lipase.

Correct Answer: C

Rationale: Rationale for Correct Answer C: Enteropeptidase converts trypsinogen to trypsin by cleaving a peptide sequence that blocks the active site of trypsin. This is crucial for the activation of trypsin, a key enzyme in protein digestion. Trypsin then activates other pancreatic enzymes. This process ensures efficient breakdown of proteins in the small intestine. Summary of Incorrect Choices: A: Pepsinogen is not secreted by the pancreas and does not require removal of a peptide sequence from the active site for activation. B: Pancreatic α-amylase is responsible for breaking down starch into maltose and not glucose. D: Pancreatic secretion of hydrochloric acid is not directly related to the activation of pancreatic enzymes; it is the role of stomach acid to provide an acidic environment for pepsin activation.