Anatomy HESI A2 Practice Test

Correct Answer: A

Rationale: The correct answer is A: They secrete chemicals into the blood. Endocrine glands are ductless glands that secrete hormones directly into the bloodstream. This allows the hormones to travel throughout the body to target organs and tissues. Choices B, C, and D are incorrect because endocrine glands do not secrete enzymes into ducts (B), produce sweat (C), or produce saliva (D). These functions are typically associated with exocrine glands that have ducts for secretion.

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: 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 correct answer is B: Hinge. The elbow joint is a hinge joint because it allows movement in only one plane, similar to a door hinge. It primarily enables flexion and extension movements. A: Ball and socket joints, like the hip joint, allow for a wider range of motion in multiple planes. C: Pivot joints, found in the neck, allow for rotational movements. D: Saddle joints, like the thumb joint, have a more complex shape that permits a variety of movements, but not present at the elbow.

Correct Answer: B

Rationale: White blood cells' main function is to fight infections. They are part of the immune system, detecting and destroying pathogens like bacteria and viruses. They do not carry oxygen (A), nutrients (C), or remove waste products (D). White blood cells play a crucial role in protecting the body from harmful invaders, making choice B the correct answer.