In the colon, the teniae coli are bands of ______, which contract to form ______.

Correct Answer: B

Rationale: The correct answer is B because the teniae coli are bands of longitudinal smooth muscle in the colon. These bands contract to form haustra, which are the pouches that give the colon its segmented appearance. Choice A is incorrect because fat and epiploic appendages are not involved in the contraction of the colon. Choice C is incorrect because the teniae coli are smooth muscle, not skeletal muscle. Choice D is incorrect because the internal anal sphincter is not formed by the contraction of the teniae coli.

Correct Answer: C

Rationale: The correct answer is C: Vitamin D. Vitamin D plays a crucial role in enhancing the absorption of calcium in the small intestine by promoting the synthesis of calcium-binding proteins. This process ensures adequate levels of calcium are absorbed efficiently. In contrast, choice A (sodium) does not directly impact calcium absorption, choice B (intrinsic factor) is involved in the absorption of vitamin B12, not calcium, and choice D (Vitamin K) is essential for blood clotting but not directly related to calcium absorption. Therefore, Vitamin D is the correct choice as it directly influences the active absorption of calcium in the small intestine.

Correct Answer: C

Rationale: The correct answer is C: Amylase. Amylase is primarily responsible for digesting carbohydrates in the small intestine. It breaks down complex carbohydrates into simpler sugars like maltose and glucose. Pepsin (A) is a stomach enzyme that breaks down proteins, not carbohydrates. Lipase (B) digests fats, not carbohydrates. Trypsin (D) is a pancreatic enzyme that digests proteins, not carbohydrates. Amylase is the only enzyme among the choices that specifically targets carbohydrates for digestion in the small intestine.

Correct Answer: C

Rationale: The correct answer is C: H+. Peptide transporter 1 requires a proton gradient for the active transport of di- and tripeptides across the enterocytes. This proton gradient is maintained by the H+ ions. Na+ (Choice A), Ca++ (Choice B), and Cl- (Choice D) are not directly involved in the transport of di- and tripeptides by peptide transporter 1. Na+ is primarily involved in glucose and amino acid transport, Ca++ in bone formation and muscle contraction, and Cl- in maintaining osmotic balance. Therefore, the correct answer is H+ as it is crucial for the functioning of peptide transporter 1.

Correct Answer: B

Rationale: The correct answer is B: cancer. T suppressor cells play a crucial role in regulating the immune response to prevent excessive activation, which can lead to the development of cancer. In cancer, T suppressor cells may become dysfunctional, allowing cancer cells to evade immune surveillance and proliferate. Autoimmune diseases (choice A) are more associated with a breakdown in immune tolerance, leading to an overactive immune response against self-antigens. Allergies (choice C) involve an exaggerated immune response to harmless substances, primarily driven by IgE antibodies and other immune cells, rather than T suppressor cells. Graft rejection (choice D) is typically mediated by T helper cells and cytotoxic T cells targeting foreign antigens present in transplanted tissues, rather than T suppressor cells.