The longest region of the small intestine is the

Correct Answer: B

Rationale: The correct answer is B: ileum. The ileum is the longest region of the small intestine, measuring about 6-7 meters in length. It is responsible for further digestion and absorption of nutrients, particularly vitamin B12 and bile salts. The duodenum is the first part of the small intestine and is relatively short, the jejunum is the middle section of the small intestine, and the colon is part of the large intestine. Therefore, the ileum is the correct answer based on its length and function in the digestive process.

Correct Answer: A

Rationale: The correct answer is A: stomach and pancreas. Firstly, protein digestion starts in the stomach where pepsinogen is converted to pepsin, breaking down proteins. Secondly, the pancreas secretes enzymes like trypsin and chymotrypsin into the small intestine to further break down proteins. The other choices are incorrect because the salivary glands primarily produce enzymes for carbohydrate digestion, while the small intestine is more involved in absorbing nutrients rather than producing protein-digesting enzymes.

Correct Answer: B

Rationale: The correct answer is B: Bile salts emulsify fat, aiding in fat digestion. Bile salts are amphipathic molecules that break down large fat globules into smaller droplets, increasing the surface area for enzymes to act upon. This enhances fat digestion and absorption. Choice A is incorrect because pepsinogen conversion is not a function of bile salts. Choice C is incorrect as bile salts are essential for digestion. Choice D is incorrect as bile salts specifically target fats, not all macromolecules.

Correct Answer: C

Rationale: The correct answer is C: gastric acid and pepsin. Gastric acid (hydrochloric acid) creates an acidic environment for pepsin, an enzyme that breaks down proteins. Bicarbonate and histamine do not directly facilitate protein digestion. Mucus protects the stomach lining. Gastric lipase aids in fat digestion, not protein digestion.

Correct Answer: B

Rationale: The correct answer is B: there would be an increase in total peripheral resistance. When sympathetic activity causes vasoconstriction in most vascular beds but not in the active skeletal muscle, it allows for increased blood flow to the muscles during exercise. If vasoconstriction did occur in the active muscle, it would impede blood flow to the muscles, leading to an increase in resistance in the peripheral circulation. This would result in an increase in total peripheral resistance, making it harder for the heart to pump blood efficiently to meet the demands of the active muscles. Choices A, C, and D are incorrect because they do not align with the physiological consequences of vasoconstriction in the active muscle during exercise.