Anatomy HESI A2 Practice Test

Correct Answer: B

Rationale: The correct answer is B: Lens. The lens of the eye is responsible for focusing light onto the retina by changing its shape to adjust the focal length. The cornea (A) helps in the initial focusing of light but does not have the ability to adjust focus. The retina (C) is the layer of cells at the back of the eye where light is converted into electrical signals, not responsible for focusing light. The pupil (D) controls the amount of light entering the eye but does not focus light onto the retina.

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.

Correct Answer: C

Rationale: Platelets' primary function is to clot blood. When a blood vessel is damaged, platelets rush to the site and form a plug to stop bleeding. Platelets release chemicals that promote clotting. Platelets do not carry oxygen (A), fight infections (B), or transport nutrients (D). Oxygen is carried by red blood cells, immunity is the function of white blood cells, and nutrients are transported by plasma.

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: Adrenal cortex. During stress, the adrenal cortex secretes cortisol and aldosterone, which help the body respond to stress. The parathyroid gland (A) regulates calcium levels, not stress hormones. The posterior pituitary gland (C) releases hormones like oxytocin and vasopressin, not stress hormones. The hypothalamus (D) plays a role in regulating the stress response by signaling the adrenal cortex to release stress hormones.