Branches of which autonomic nerve carry the parasympathetic motor neurons to the enteric plexi?

Correct Answer: D

Rationale: The correct answer is D: vagus. The vagus nerve carries parasympathetic motor neurons to the enteric plexi located in the gastrointestinal tract. It innervates most of the organs in the thorax and abdomen, controlling functions like digestion and heart rate. Choices A, B, and C are incorrect because they do not carry parasympathetic motor neurons to the enteric plexi. Oculomotor (A) innervates muscles responsible for eye movement, facial (B) innervates facial muscles and salivary glands, and glossopharyngeal (C) innervates the tongue and pharynx, but they do not specifically target the enteric plexi in the gastrointestinal tract.

Correct Answer: C

Rationale: The correct answer is C: chief or zymogenic cells. These cells are responsible for producing pepsinogen, the inactive form of pepsin, which is an enzyme that helps in protein digestion. Chief cells secrete pepsinogen into the gastric lumen. Endocrine cells (A) produce hormones like gastrin, mucous neck cells (B) secrete mucus to protect the stomach lining, and parietal cells (D) secrete hydrochloric acid to create an acidic environment for pepsinogen activation. Therefore, the correct choice is C as it directly produces pepsinogen.

Correct Answer: B

Rationale: The correct answer is B: the feces to contain a much higher percentage of fat than normal. The hepatopancreatic ampullar sphincter controls the release of bile and pancreatic enzymes into the duodenum to aid in fat digestion. If it does not relax, fat digestion would be impaired, leading to undigested fat in feces. A: Chyme is the semi-liquid mixture of food and digestive juices in the stomach, not affected by this sphincter. C: Starch and protein digestion mainly occur in the stomach and small intestine, not directly influenced by this sphincter. D: Chyme enters the large intestine after passing through the small intestine, not controlled by this sphincter directly.

Correct Answer: A

Rationale: The correct answer is A: intercalated duct. The aqueous component of pancreatic juice is produced by intercalated ducts, which are responsible for secreting bicarbonate-rich fluid to neutralize the acidic chyme entering the duodenum. Other choices are incorrect because pancreatic islets (B) secrete hormones like insulin and glucagon, acinar cells (C) secrete digestive enzymes, and the duodenum (D) is the first part of the small intestine where pancreatic juice is delivered but not where it is produced.

Correct Answer: C

Rationale: The correct answer is C: low-density lipoproteins (LDL). LDL carries cholesterol to tissues where it is needed for steroid synthesis and bile salt production. LDL is known as the "bad" cholesterol transporter because high levels can lead to plaque buildup in arteries. Micelles (A) are small lipid droplets in the intestine, chylomicrons (B) transport dietary fats, and HDL (D) is known as the "good" cholesterol transporter that helps remove excess cholesterol from the bloodstream.