HESI A2 Anatomy and Physiology 2023

Correct Answer: B

Rationale: The correct answer is B: Hinge joint. The knee joint is classified as a hinge joint because it primarily allows movement in one plane, similar to a door hinge. This type of joint permits flexion and extension movements, which are the main actions of the knee. The other choices are incorrect because: A: Ball and socket joint allows for multi-directional movement, such as the hip joint. C: Pivot joint allows for rotation around an axis, like the joint between the radius and ulna bones in the forearm. D: Saddle joint allows for movements in two planes, like the joint at the base of the thumb.

Correct Answer: A

Rationale: The correct answer is A: Cochlea. The cochlea is responsible for detecting sound as it contains hair cells that convert sound vibrations into electrical signals sent to the brain. The Eustachian tube helps equalize pressure, the ossicles transmit sound waves to the cochlea, and the semicircular canals are responsible for balance and spatial orientation. Choose A because the cochlea is specifically designed for detecting sound through its intricate inner workings.

Correct Answer: A

Rationale: The correct answer is A: Cerebellum. The cerebellum is responsible for controlling balance and coordination. It receives information from the sensory systems, such as the inner ear and visual system, and integrates this information to coordinate smooth movements. The cerebrum (B) is mainly involved in higher brain functions like thinking and problem-solving. The medulla oblongata (C) controls vital functions such as breathing and heart rate. The brainstem (D) is responsible for basic life functions like breathing and consciousness. Thus, the cerebellum is the specific region of the brain that directly controls balance and coordination.

Correct Answer: B

Rationale: The correct answer is B: White blood cells. White blood cells, also known as leukocytes, are primarily responsible for fighting infections by detecting and destroying pathogens. Red blood cells (A) carry oxygen, platelets (C) aid in blood clotting, and plasma (D) is the liquid component of blood carrying nutrients and waste. White blood cells play a crucial role in the immune system's defense against infections, making them the correct choice.

Correct Answer: B

Rationale: The correct answer is B: Parathyroid hormone. Parathyroid hormone is produced by the parathyroid glands and plays a crucial role in regulating calcium levels in the blood. It does so by increasing calcium absorption in the intestines, reabsorption in the kidneys, and release from bones. Insulin (choice A) regulates blood sugar, not calcium. Cortisol (choice C) is a stress hormone and does not directly affect calcium levels. Melatonin (choice D) regulates sleep-wake cycles and does not play a role in calcium regulation. Therefore, the correct choice is B as it directly influences calcium levels in the blood.