It is true to say the following about the motility of the gastrointestinal system:

Correct Answer: D

Rationale: The correct answer is D because peristalsis, a coordinated muscle contraction that propels food along the gastrointestinal tract, is indeed seen in most parts of the GIT. This process helps move food from the esophagus to the stomach, and then throughout the intestines for digestion and absorption. Peristalsis is essential for the proper functioning of the digestive system. Choice A is incorrect because gastrointestinal motility is regulated by both neural and hormonal factors. Choice B is incorrect as the emptying of the stomach is mainly facilitated by the rhythmic contractions of the stomach muscles, not segmentation contractions. Choice C is incorrect as the movement of chyme along the small intestine is primarily due to segmentation and peristalsis, not the migrating motor complex.

Correct Answer: C

Rationale: The Mallory-Weiss syndrome is characterized by mucosal tears at the esophagogastric junction. This occurs due to forceful or prolonged vomiting causing the tears in the mucosa. Esophageal varices (A) are dilated veins in the esophagus typically associated with liver disease, not related to Mallory-Weiss syndrome. Esophageal peptic ulcers (B) are erosions in the lining of the esophagus caused by acid reflux or infection, not a characteristic of Mallory-Weiss syndrome. Iatrogenic perforation (D) refers to accidental perforation caused during a medical procedure, not related to Mallory-Weiss syndrome. Therefore, the correct answer is C as it directly correlates with the characteristic presentation of Mallory-Weiss syndrome.

Correct Answer: A

Rationale: The correct answer is A because Clostridium difficile produces toxins, specifically enterotoxins, which cause damage to the intestinal mucosa leading to pseudo-membranous colitis. The organism colonizes the colon and then elaborates the toxins, which disrupt the mucosal barrier. Choice B is incorrect as there is no preformed toxin ingested; the toxin is produced by the organism after colonization. Choice C is incorrect as Clostridium difficile does not invade and destroy the mucosa directly. Choice D is incorrect as the host immune response is a consequence of the toxin production, not the primary mechanism of disease.

Correct Answer: B

Rationale: The correct answer is B: Gastrin stimulates HCL secretion. Gastrin is a hormone released from the stomach, not the duodenum. It acts to increase the secretion of hydrochloric acid (HCL) in the stomach, aiding in digestion. Gastrin also accelerates stomach emptying, contrary to choice C. Therefore, options A and C are incorrect. Choice D is incorrect as well because only option B is correct.

Correct Answer: C

Rationale: The correct answer is C: Bile salts are produced by the liver from cholesterol. Rationale: 1. Bile salts aid in the emulsification and digestion of fats, not proteins (A). 2. Pancreatic amylase is responsible for carbohydrate digestion, not bile salts (B). 3. The liver synthesizes bile salts from cholesterol to facilitate fat digestion and absorption (C). 4. Bile salts reduce lipid surface tension to form micelles, aiding in fat digestion, rather than increasing it (D).