Which part of the digestive system absorbs most nutrients?

Correct Answer: A

Rationale: The correct answer is A: Small intestine. The small intestine is where most of the absorption of nutrients occurs due to its large surface area and presence of villi and microvilli. These structures increase the absorption capacity, allowing for efficient absorption of nutrients like carbohydrates, proteins, fats, vitamins, and minerals. The stomach primarily functions in the digestion of food through the action of stomach acid and enzymes, while the large intestine mainly absorbs water and electrolytes. The mouth is responsible for initial digestion through chewing and production of saliva but does not play a significant role in nutrient absorption.

Correct Answer: C

Rationale: Rationale: The stomach primarily functions in digestion and does not have significant absorption capabilities. Glucose is absorbed in the small intestine through specialized transport mechanisms. Choices A (Ca) and D (aromatic amino acids) are primarily absorbed in the small intestine as well. Alcohol is absorbed in the stomach to a small extent, but the majority is absorbed in the small intestine. Therefore, the correct answer is C (Glucose) as it is primarily absorbed in the small intestine, not the stomach.

Correct Answer: C

Rationale: Congenital lesions causing vomiting in the first three days include pyloric stenosis and intestinal atresia. Pyloric stenosis typically presents with non-bilious projectile vomiting in the first few weeks of life, while intestinal atresia presents with bilious vomiting shortly after birth. Therefore, the correct answer is C, as both conditions can manifest with vomiting within the first three days of life. Choice A and B alone are incorrect because they each only represent one of the conditions, and choice D is incorrect as both conditions can present with vomiting in the specified time frame.

Correct Answer: D

Rationale: The correct answer is D: appendix. Carcinoid tumors in the appendix are considered the most benign due to their slow growth rate and low metastatic potential. The appendix is a small organ with limited blood supply, which restricts tumor growth and dissemination. Other choices (A: stomach, B: small intestine, C: rectum) have higher malignant potential due to larger size, increased blood supply, and higher likelihood of metastasis. Therefore, the appendix is the most benign location for carcinoid tumors.

Correct Answer: A

Rationale: Rationale: A) Lactase, maltase, and sucrase enzymes are secreted in the small intestine to break down lactose, maltose, and sucrose into simpler sugars for absorption. B) Glucose and amino acids absorption occurs via active transport, not simple diffusion. C) Bile pigments are not completely absorbed; they aid in fat digestion. D) Fat absorption is primarily a passive process, with some active transport involved, but it does not require a Na co-transport system.