Anatomy HESI A2 Practice Test

Correct Answer: B

Rationale: The correct answer is B: To break down food. The stomach's main role in digestion is to mechanically and chemically break down food into smaller particles through the churning action of muscles and the secretion of gastric juices containing hydrochloric acid and enzymes. This process prepares the food for further digestion and absorption in the small intestine. Explanation for incorrect choices: A: To absorb nutrients - Absorption of nutrients primarily occurs in the small intestine, not the stomach. C: To secrete digestive enzymes - While the stomach does secrete digestive enzymes, its main function is to break down food, not just to secrete enzymes. D: To transport nutrients - Nutrient absorption and transportation occur in the small intestine, not the stomach.

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: 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: B

Rationale: The correct answer is B: Semicircular canals. These structures in the inner ear are responsible for detecting rotational movement and maintaining balance. The semicircular canals contain fluid that moves in response to head movements, stimulating hair cells that send signals to the brain about the body's position in space. A: The cochlea is responsible for hearing, not balance. C: Ossicles are tiny bones in the middle ear that transmit sound vibrations to the cochlea. D: The Eustachian tube helps equalize pressure in the middle ear and is not directly related to balance. In summary, the semicircular canals are crucial for maintaining balance by detecting rotational movements, while the other structures mentioned are primarily involved in hearing or pressure regulation.

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.