Contractions of the smooth muscles in the tunica muscularis in the GI tract causes ______ and is stimulated by ______ plexus.

Correct Answer: B

Rationale: The correct answer is B because contractions of smooth muscles in the GI tract lead to peristalsis, the movement that propels food through the digestive system. These contractions are stimulated by the Auerbach's or myenteric plexus, which are responsible for coordinating muscle movements in the gut. Choice A is incorrect as local secretions do not directly cause muscle contractions. Choice C is incorrect because peristalsis is the result of muscle contractions, not local secretions. Choice D is incorrect as local secretions are not the primary stimulus for muscle contractions in the GI tract.

Correct Answer: A

Rationale: The correct answer is A: epiglottis is not closed over the glottis. When talking and eating simultaneously, the epiglottis fails to close over the glottis, leading to some of the food or liquid entering the larynx instead of being directed towards the esophagus. The epiglottis normally acts as a lid to cover the larynx during swallowing, preventing food or liquid from entering the airway. Therefore, failure of the epiglottis to close properly during talking and eating can trigger the gagging reflex. Summary of why the other choices are incorrect: B: Soft palate moving inferiorly is associated with the process of swallowing and closing off the nasopharynx, not the larynx. C: Pharyngeal constrictor muscles relax would not lead to food entering the larynx during talking and eating; in fact, they contract to propel food downwards. D: Esophageal sphinct

Correct Answer: C

Rationale: Rationale: 1. Simple columnar epithelium: Lines the inner surface of the GI tract for absorption. 2. Muscularis mucosa: Thin layer of smooth muscle for mucosal movement. 3. Meissner's plexus: Submucosal nerve plexus for controlling secretions. 4. Two layers of smooth muscle in the tunica muscularis: Helps in peristalsis. 5. Peyer's patches of lymph nodules: Part of the immune system in the GI tract, mainly found in the ileum for protection against pathogens. Therefore, the correct answer is C: ileum, as it has all the mentioned characteristics. Summary: A: duodenum - Lacks Peyer's patches and two layers of smooth muscle. B: jejunum - Lacks Meissner's plexus and Peyer's patches. D: colon - Lacks simple columnar epithelium, Meissner's plexus

Correct Answer: A

Rationale: The correct answer is A: cholesterol. Gallstones are primarily formed from the precipitation of cholesterol in the gallbladder due to imbalances in bile components. Cholesterol stones are the most common type of gallstones. Calcium salts (B) can contribute to gallstone formation but are not the primary component. Uric acid salts (C) are associated with kidney stones, not gallstones. Urea (D) is a waste product excreted in urine and is not involved in gallstone formation.

Correct Answer: C

Rationale: The correct answer is C: bile salts; lipase. Bile salts emulsify lipids by breaking them down into smaller droplets to increase the surface area for digestion by lipase. Lipase is the enzyme responsible for digesting lipids into fatty acids and glycerol. Option A is incorrect because lipase digests lipids, not bile salts. Option B is incorrect because amylase digests carbohydrates, not lipids. Option D is incorrect because pepsin is an enzyme that digests proteins, not lipids.