What is the primary function of the skeletal system?

Correct Answer: B

Rationale: The primary function of the skeletal system is to protect vital organs, provide structural support, and enable movement. It serves as a framework that supports and protects internal organs, such as the brain, heart, and lungs. Choice A is incorrect because blood cell production primarily occurs in the bone marrow, a component of the skeletal system but not its primary function. Choice C is incorrect because fat storage is not a primary function of the skeletal system. Choice D is incorrect because hormone secretion is mainly regulated by endocrine glands, not the skeletal system.

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: Platelets, also known as thrombocytes, are cell fragments that play a crucial role in blood clotting and wound healing. They are responsible for forming blood clots to stop bleeding when a blood vessel is injured, making them the correct choice in this context. Red blood cells (Choice A) are primarily involved in oxygen transport, white blood cells (Choice B) are part of the immune system, and plasma (Choice D) is the liquid component of blood that carries various substances.

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.