Anatomy HESI A2 Practice Test

Correct Answer: B

Rationale: The correct answer is B: Thymus. The thymus is not a principal organ of the nervous system; it is part of the immune system. The brain (A), ganglia (C), and spinal cord (D) are all essential components of the nervous system. The brain is the main control center, ganglia are clusters of nerve cell bodies outside the central nervous system, and the spinal cord is a major pathway for transmitting nerve signals. Therefore, the thymus stands out as the only choice that is not directly related to the nervous system, making it the correct answer in this context.

Correct Answer: B

Rationale: The primary function of the alveoli in the lungs is to exchange oxygen and carbon dioxide. This process occurs through diffusion, where oxygen moves from the alveoli into the bloodstream, and carbon dioxide moves from the bloodstream into the alveoli to be exhaled. This exchange is essential for oxygenating the blood and removing carbon dioxide, maintaining proper gas exchange in the body. Why the other choices are incorrect: A: Alveoli do play a role in removing carbon dioxide, but their primary function is the exchange of oxygen and carbon dioxide. C: While alveoli do transport oxygen to the bloodstream, they also exchange carbon dioxide, making this choice incomplete. D: Alveoli do not filter blood; their main function is gas exchange in the lungs.

Correct Answer: B

Rationale: The correct answer is B: To speed up chemical reactions. Enzymes act as biological catalysts that accelerate chemical reactions by lowering the activation energy required for the reactions to occur. They do not produce energy (choice A), transport molecules (choice C), or repair tissues (choice D). Enzymes specifically facilitate reactions without being consumed in the process, making them crucial for various metabolic pathways in the body.

Correct Answer: A

Rationale: The correct answer is A: Parathyroid gland. When under stress, hormones like cortisol and adrenaline are released primarily from the adrenal cortex and the hypothalamus-pituitary-adrenal (HPA) axis. The posterior pituitary releases oxytocin and vasopressin, which are not directly related to stress response. The parathyroid gland, on the other hand, regulates calcium levels in the blood and is not directly involved in the stress response.

Correct Answer: A

Rationale: The primary function of the cardiovascular system is to pump blood throughout the body. This process ensures oxygen and nutrients are delivered to tissues and organs, while also removing waste products. Choice A is correct as it directly relates to the main role of the cardiovascular system. Choices B, C, and D are incorrect because although the cardiovascular system indirectly contributes to delivering nutrients, regulating body temperature, and protecting against infection through immune responses, these are not its primary functions.