Which part of the digestive system is responsible for absorbing the majority of water?

Correct Answer: C

Rationale: The correct answer is C: large intestine. The large intestine is responsible for absorbing the majority of water in the digestive system. This occurs in the colon, where water is reabsorbed from the indigestible food residue, turning it into solid waste. The stomach (A) primarily breaks down food, the small intestine (B) absorbs nutrients, and the rectum (D) stores feces before elimination. Therefore, the large intestine is the correct choice for water absorption in the digestive process.

Correct Answer: A

Rationale: Cholecystokinin (CCK) is released after a meal to stimulate the release of bile from the gallbladder into the small intestine to aid in digestion and absorption of fats. This process is crucial for emulsifying fats and enhancing their digestion. Choice A is correct because it directly aligns with the primary function of CCK. Choices B, C, and D are incorrect because CCK does not play a role in stimulating gastric acid secretion, insulin release, or absorption of nutrients. These functions are typically controlled by other hormones such as gastrin, insulin, and various enzymes in the digestive system.

Correct Answer: B

Rationale: The correct answer is B: Liver. The liver is an accessory digestive organ as it produces bile, which aids in the digestion and absorption of fats in the small intestine. The other choices, A: Esophagus, C: Stomach, and D: Small intestine, are primary digestive organs involved directly in the process of digestion and absorption of nutrients. The esophagus is responsible for transporting food to the stomach, the stomach digests food with gastric juices, and the small intestine is where most of the digestion and absorption of nutrients occur. Therefore, the liver stands out as the correct answer as it supports the digestive process rather than directly participating in it.

Correct Answer: B

Rationale: The correct answer is B: Common bile duct. Gas is not typically present in the common bile duct in a normal healthy individual. The presence of gas in the stomach (A), small intestine (C), and transverse colon (D) is expected due to normal digestive processes. Gas in the common bile duct could indicate an abnormality such as a blockage or infection. Therefore, the absence of gas in the common bile duct on an X-ray of a normal healthy man is expected.

Correct Answer: C

Rationale: The correct answer is C: Lactose. Brush border enzymes in the small intestine, specifically lactase, digest lactose into its component sugars, glucose, and galactose. Lactose is a disaccharide found in dairy products that needs to be broken down for absorption. Starch (A) is primarily digested by salivary and pancreatic amylase. Cholesterol esters (B) are broken down by pancreatic enzymes. Galactose (D) is a monosaccharide that is a product of lactose digestion, not directly digested by brush border enzymes.