Salivary secretion is stimulated by

Correct Answer: D

Rationale: The correct answer is D. Salivary secretion is stimulated by the salivary nucleus in the brainstem and local reflexes in the tunica mucosa and submucosa of the oral cavity. The salivary nucleus receives input from higher brain centers and initiates the salivary reflex. Local reflexes in the oral cavity, such as mechanical stimulation of the mucosa, also trigger salivary secretion. Gastrin, as mentioned in option B and C, is not directly involved in the stimulation of salivary secretion. Option A is incorrect as salivary secretion is not solely stimulated by the salivary nucleus. Option D encompasses the comprehensive stimulation pathways involved in salivary secretion.

Correct Answer: B

Rationale: The correct answer is B because bile salts emulsify fat into smaller droplets, increasing the surface area for enzymes to break down fats into fatty acids and glycerol. This aids in fat digestion and absorption in the small intestine. Choice A is incorrect as bile salts do not directly break down fats into fatty acids and glycerol. Choice C is incorrect as bile salts do not break down fats into cholesterol and lecithin. Choice D is incorrect as bile salts do not emulsify fats to bilirubin, but rather help in the digestion of fats.

Correct Answer: D

Rationale: The correct answer is D: bacteria. Enzymes in the large intestine are primarily produced by the gut microbiota, which are bacteria residing in the colon. These bacteria play a crucial role in the breakdown of complex carbohydrates and the production of certain vitamins, including Vitamin K. Goblet cells (A) produce mucus, simple columnar cells (B) are involved in absorption, and teniae coli (C) are muscle bands in the colon - none of which are directly responsible for enzyme production or Vitamin K synthesis in the large intestine.

Correct Answer: A

Rationale: The correct answer is A because dietary starch does not cause insulin release from the pancreas, but rather stimulates the release of incretin hormones like glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These incretins help regulate blood sugar levels postprandially and do not directly affect intestinal motility. Incorrect choices: B: Food in the stomach causing gastrin release is true and stimulates acid secretion. C: Short-chain fatty acids moving from colon to caecum promoting ileo-caecal motility is true. D: The arrival of lipid in the duodenum causing a reduction in motility is true.

Correct Answer: D

Rationale: The correct answer is D because the extrinsic salivary glands are the parotid, submandibular, and sublingual glands. The parotid gland is located near the ear, the submandibular gland is under the mandible, and the sublingual gland is under the tongue. A is incorrect because the ethmoidal gland is not an extrinsic salivary gland. B is incorrect because the buccal gland is not an extrinsic salivary gland. C is incorrect because the buccal gland is not an extrinsic salivary gland; it is a minor salivary gland located in the cheek.