The lamina propria and muscularis mucosa are found in the tunica

Correct Answer: A

Rationale: The lamina propria and muscularis mucosa are components of the mucosa layer. The lamina propria is a layer of connective tissue beneath the epithelium, while the muscularis mucosa is a thin layer of smooth muscle. Both are part of the mucosa, which is the innermost layer of the gastrointestinal tract. Therefore, the correct answer is A: mucosa. The other choices are incorrect because the submucosa (B) is located outside the mucosa layer, the muscularis (C) is a separate layer of smooth muscle outside the mucosa, and the serosa (D) is the outermost layer of the gastrointestinal tract.

Correct Answer: A

Rationale: The correct answer is A: peristaltic reflex. During the esophageal phase of swallowing, peristalsis is the coordinated contraction and relaxation of muscles that propels food down the esophagus. This reflex is initiated by the stretching of the esophageal wall when food bolus enters, triggering a series of contractions to move the bolus towards the stomach. The enteric reflex (B) involves local reflexes within the gut but is not specific to the esophageal phase of swallowing. The swallowing center (C) in the medulla oblongata coordinates the overall swallowing process but does not directly cause the esophageal phase. The coughing reflex (D) is a protective mechanism to clear the airway, not involved in the esophageal phase.

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.