Which of the following drugs is an antacid?

Correct Answer: D

Rationale: The correct answer is D, Magnesium Hydroxide (Maalox), as it is an antacid that works by neutralizing stomach acid. Omeprazole (A) is a proton pump inhibitor that reduces acid production, not neutralizes it. Metoclopramide (B) is a prokinetic agent used for gastrointestinal motility disorders. Cimetidine (C) is an H2 receptor antagonist that decreases stomach acid production but doesn't directly neutralize acid like an antacid. Therefore, D is the correct choice as it directly acts to neutralize stomach acid.

Correct Answer: D

Rationale: The correct answer is D because all of the choices activate sensors in the walls of digestive organs. A: Breakdown products of digestion trigger chemoreceptors. B: Distension activates mechanoreceptors in response to stretching of the organ walls. C: pH of chyme activates pH receptors. Therefore, all three stimuli play a role in signaling the digestive system to regulate processes like secretion and motility.

Correct Answer: B

Rationale: The correct answer is B: proximal small intestine. Most digestion occurs in the proximal small intestine due to the presence of enzymes such as amylase, lipase, and protease, which break down carbohydrates, fats, and proteins, respectively. Additionally, bile and pancreatic juices are released in this part of the intestine to aid in digestion. The stomach primarily initiates digestion by breaking down food with stomach acid and enzymes, but the majority of nutrient absorption occurs in the small intestine. Choices A, C, and D are incorrect as the stomach is not the main site of digestion, the distal small intestine is more focused on absorption rather than digestion, and the ascending colon is primarily responsible for water absorption and formation of feces.

Correct Answer: C

Rationale: The correct answer is C: esophagus. An accessory organ is one that aids in digestion but is not part of the digestive tract. The esophagus is part of the digestive tract, responsible for transporting food from the mouth to the stomach. The pancreas, liver, and gallbladder are all accessory organs as they play a role in digestion but are not directly part of the digestive tract. Pancreas produces enzymes for digestion, liver produces bile for fat digestion, and gallbladder stores and releases bile. Therefore, the esophagus is the correct answer as it is not an accessory organ.

Correct Answer: D

Rationale: The correct answer is D: muscularis. The muscularis layer of the intestinal wall is responsible for peristalsis, the wave-like contractions that propel food through the digestive tract. The mucosa (A) is the innermost layer involved in absorption, not movement. The submucosa (B) provides support and nourishment to the mucosa. The adventitia (C) refers to connective tissue that surrounds organs, not directly involved in movement. Therefore, the muscularis (D) is the only layer specifically responsible for changing the shape of the intestinal lumen and moving food along its length.