Which vitamin is essential for immune system function?

Correct Answer: C

Rationale: Vitamin D is the correct answer. It is essential for immune system function as it helps regulate and support the immune response. Vitamin D plays a crucial role in calcium absorption, which is necessary for maintaining strong and healthy bones. Vitamin A is important for vision and skin health, not specifically immune function. Vitamin C is known for its antioxidant properties and its role in collagen production, not primarily for immune system function. Vitamin K is essential for blood clotting and bone health, but it is not directly related to immune system function.

Correct Answer: C

Rationale: Smooth muscle tissue is found in the walls of hollow organs, such as the intestines, blood vessels, and bladder. It contracts involuntarily, allowing for movements like peristalsis in the intestines and regulation of blood flow in blood vessels. Skeletal muscle (Choice A) is attached to bones and helps in voluntary movements. Cardiac muscle (Choice B) is found in the heart and contracts involuntarily to pump blood. Striated muscle (Choice D) refers to both skeletal and cardiac muscles, which have a striped appearance due to the organization of their filaments. However, smooth muscle (Choice C) is specifically the type found in hollow organs.

Correct Answer: B

Rationale: The correct answer is B, Cortisol. Cortisol is the hormone produced by the adrenal cortex. It plays a crucial role in regulating metabolism, immune response, and managing stress. Insulin is produced by the pancreas, thyroxine by the thyroid gland, and glucagon by the pancreas. Therefore, choices A, C, and D are incorrect as they are not hormones produced by the adrenal cortex.

Correct Answer: B

Rationale: Vitamin D is crucial for the absorption of calcium in the intestines, which is vital for maintaining strong bones and teeth. It helps regulate calcium levels in the blood and promotes bone mineralization, making it an essential vitamin for overall bone health. Vitamin A (Choice A) is important for vision and immune function, not specifically for calcium absorption. Vitamin K (Choice C) is essential for blood clotting, while Vitamin C (Choice D) is known for its role in collagen production and antioxidant properties, but not directly related to calcium absorption.

Correct Answer: A

Rationale: Insulin is the hormone released by the pancreas to lower blood glucose levels. Insulin facilitates the uptake of glucose into cells, helping to decrease blood glucose levels and store excess glucose for energy or future use. Glucagon, on the other hand, raises blood glucose levels by promoting the breakdown of glycogen into glucose. Cortisol and somatostatin do not directly regulate blood glucose levels in the same manner as insulin and glucagon.