Which of these nutrients is absorbed mainly in the duodenum?

Correct Answer: B

Rationale: The correct answer is B: iron. Iron is mainly absorbed in the duodenum, the first part of the small intestine. Here's the rationale: 1. Duodenum is where iron absorption begins. 2. Iron is absorbed through the duodenal mucosal cells. 3. The acidic environment in the duodenum enhances iron absorption. 4. Other nutrients like glucose are mainly absorbed in the small intestine but not specifically in the duodenum. 5. Sodium and water are primarily absorbed in the small intestine, with water being absorbed throughout the digestive tract.

Correct Answer: C

Rationale: The correct answer is C: formation and elimination of feces. The main function of the large intestine is to absorb water and electrolytes, form feces by compacting and storing waste material, and eliminate feces through defecation. This process helps maintain the body's fluid balance and eliminates waste. Choices A, B, and D are incorrect because absorption of nutrients primarily occurs in the small intestine, secretion of digestive enzymes mainly occurs in the stomach and small intestine, and digestion of proteins mainly occurs in the stomach and small intestine, not the large intestine.

Correct Answer: C

Rationale: The correct answer is C: The liver detoxifies drugs and alcohol. The liver contains enzymes that break down harmful substances, helping to remove toxins from the body. This process is essential for maintaining overall health. Choice A is incorrect because the pancreas, not the liver, produces digestive enzymes. Choice B is also incorrect because the gallbladder, not the liver, stores bile. Choice D is incorrect because the pancreas, not the liver, produces insulin to regulate blood sugar levels.

Correct Answer: B

Rationale: The correct answer is B: Small intestine. The small intestine is where most nutrient absorption occurs due to its large surface area, specialized villi, and microvilli that increase absorption efficiency. Digestive enzymes and bile are also secreted here to further break down nutrients. Stomach (A) primarily aids in digestion, not absorption. Large intestine (C) mainly absorbs water and electrolytes, not nutrients. Mouth (D) begins the digestion process by mechanical breakdown and some enzyme release, but minimal absorption occurs here.

Correct Answer: A

Rationale: The correct answer is A: Vagal stimulation. Vagal stimulation does not directly increase the secretion of the exocrine pancreas. Acetylcholine, Secretin, and CCK are known to stimulate pancreatic secretion through various mechanisms. Acetylcholine acts through muscarinic receptors, Secretin is released in response to acidic chyme in the duodenum, and CCK is released in response to fat and proteins in the duodenum, all leading to increased pancreatic enzyme secretion. Vagal stimulation plays a role in the parasympathetic nervous system but does not directly stimulate pancreatic secretion.