ATI Anatomy and Physiology

Correct Answer: A

Rationale: Platelets play a crucial role in hemostasis by forming plugs to stop bleeding. Choice B is incorrect because platelets do not promote vasodilation; instead, they help in vasoconstriction. Choice C is incorrect as the conversion of prothrombin to thrombin is a function of the coagulation cascade involving various clotting factors, not platelets. Choice D is incorrect as platelets do not directly activate calcium; instead, they play a role in the activation of other clotting factors.

Correct Answer: D

Rationale: The correct answer is D: Antidiuretic hormone. Antidiuretic hormone (ADH), also known as vasopressin, is produced by the hypothalamus and stored in the posterior pituitary gland. It plays a key role in regulating the body's water balance by controlling the amount of water reabsorbed by the kidneys. Choices A, B, and C are incorrect because Growth hormone is produced by the anterior pituitary gland, Luteinizing hormone is produced by the anterior pituitary gland, and Adrenocorticotropic hormone is produced by the anterior pituitary gland.

Correct Answer: D

Rationale: Macrophages are a type of white blood cell that plays a crucial role in the immune system by engulfing and digesting cellular debris, foreign substances, microbes, cancer cells, and old or damaged cells. Basophils are primarily involved in allergic reactions and parasitic infections, eosinophils combat multicellular parasites and have a role in allergic reactions, and B-cells are responsible for producing antibodies. Therefore, the correct answer is macrophages as they are specialized in phagocytosis and removal of unwanted cells and microorganisms.

Correct Answer: C

Rationale: Peripheral vasodilation is the widening of blood vessels near the surface of the skin, allowing more blood to flow near the skin's surface. This process enhances heat loss primarily through radiation. Radiation is the transfer of heat energy in the form of electromagnetic waves. Conduction involves direct contact between objects, convection involves the transfer of heat through fluid or gas, and evaporation involves the phase change of a liquid to a gas, which cools the surface.

Correct Answer: B

Rationale: The correct answer is the Medulla Oblongata. This part of the brain is responsible for regulating essential autonomic functions such as heart rate, respiratory rate, and blood pressure. The Corpus Callosum is responsible for connecting the left and right hemispheres of the brain, not for regulating these vital functions. The Pituitary Glands and Pineal Glands are part of the endocrine system and are not directly involved in regulating heart rate, respiratory rate, and blood pressure.