The duodenum and jejunum are the main site for absorption of the following except:

Correct Answer: D

Rationale: The correct answer is D: Bile salts. Bile salts are primarily absorbed in the terminal ileum, not in the duodenum or jejunum. The duodenum and jejunum are mainly responsible for absorbing nutrients like glucose, fat-soluble vitamins, and vitamin C. Bile salts aid in the digestion and absorption of fats, but they are reabsorbed in the ileum to be recycled. Therefore, the duodenum and jejunum are not the main sites for the absorption of bile salts.

Correct Answer: C

Rationale: The correct answer is C: Saliva contains alpha amylase. Saliva does indeed contain the enzyme alpha amylase, which helps in the breakdown of carbohydrates in the mouth. This is a well-established fact in human physiology. Explanation for why other choices are incorrect: A: HCL converts pepsin into pepsinogen - This statement is incorrect as pepsinogen is converted into pepsin by the acidic environment in the stomach, not the other way around. B: IF is essential for vitamin K absorption - This is also incorrect. Intrinsic factor (IF) is essential for the absorption of vitamin B12, not vitamin K. D: Myenteric plexus controls GIT secretion - While the myenteric plexus is involved in regulating gastrointestinal motility, it is not primarily responsible for controlling secretion in the gastrointestinal tract.

Correct Answer: B

Rationale: Step 1: HCL helps in the digestion of food by creating an acidic environment in the stomach. Step 2: This acidic environment aids in the breakdown of food components, including iron. Step 3: Iron absorption is enhanced in the presence of HCL. Conclusion: Choice B is correct as HCL helps in the absorption of iron. Choices A, C, and D are incorrect as HCL does not inhibit pepsinogen, aid in absorption of vitamin B12, or secreted in response to sympathetic stimulation.

Correct Answer: B

Rationale: The correct answer is B: Rugae, Increase. Rugae are folds in the mucosa of the stomach that allow for expansion of the stomach when food is ingested, increasing the surface area for digestion and absorption. Rugae help in mixing and breaking down food efficiently. Explanation: 1. Rugae are specifically found in the stomach to increase surface area for digestion. 2. The folds of rugae help in stretching the stomach to accommodate food intake. 3. Increased surface area aids in better absorption of nutrients. 4. Crypts are invaginations in the mucosa but not related to increasing surface area. 5. Option C and D are incorrect because rugae actually increase, not decrease, the surface area of the stomach.

Correct Answer: A

Rationale: The correct answer is A: Amylase. Amylase is responsible for breaking down carbohydrates in the mouth during digestion. It is produced in the salivary glands and helps to break down complex carbohydrates into simpler sugars like maltose. Lipase (B) breaks down fats, pepsin (C) breaks down proteins, and trypsin (D) is an enzyme that also breaks down proteins but is produced in the pancreas, not in the mouth. Amylase is the only enzyme among the choices that specifically targets carbohydrates in the mouth, making it the correct answer.