HESI A2 Anatomy and Physiology 2023

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: B: Vitamin B12 is essential for the formation of red blood cells as it plays a key role in the production of red blood cells in the bone marrow. It is necessary for the proper development and maintenance of red blood cells, which carry oxygen throughout the body. Vitamin A supports vision and immune function, not red blood cell formation. Vitamin C aids in collagen formation and immune function. Vitamin D helps in calcium absorption and bone health. Therefore, B is the correct choice for red blood cell formation.

Correct Answer: B

Rationale: The correct answer is B: Thyroxine. Thyroxine, produced by the thyroid gland, plays a key role in regulating metabolism by controlling the body's metabolic rate. It influences how fast or slow our cells use energy. Insulin (A) regulates blood sugar levels, not metabolism. Glucagon (C) raises blood sugar levels. Cortisol (D) is a stress hormone that affects various body functions but is not primarily responsible for regulating metabolism. Thyroxine is crucial for maintaining overall metabolic balance in the body.

Correct Answer: B

Rationale: The gallbladder's function is to store and concentrate bile produced by the liver. When food is ingested, the gallbladder releases bile into the small intestine to aid in the digestion and absorption of fats. Choice A is incorrect because the liver produces bile. Choice C is incorrect as the liver, not the gallbladder, is responsible for detoxifying harmful substances. Choice D is also incorrect as blood sugar regulation is mainly controlled by the pancreas and hormones like insulin and glucagon.

Correct Answer: B

Rationale: The correct answer is B: Thyroid gland. The thyroid gland produces hormones such as thyroxine (T4) and triiodothyronine (T3), which regulate metabolism by controlling the body's energy production and utilization. The pituitary gland (A) regulates various other hormones but not specifically metabolism. The adrenal gland (C) produces hormones like cortisol and adrenaline, which are involved in stress response, not metabolism. The pineal gland (D) produces melatonin, which regulates sleep-wake cycles, not metabolism. Therefore, the thyroid gland is the correct answer as it directly controls metabolic functions.