HESI A2 Anatomy and Physiology 2023

Correct Answer: C

Rationale: The correct answer is C: Retina. The retina contains specialized cells called cones that are responsible for color vision. Cones are sensitive to different wavelengths of light, allowing us to perceive colors. The cornea (A) focuses light onto the retina, the iris (B) controls the amount of light entering the eye, and the lens (D) helps to focus light onto the retina, but they do not directly contribute to color vision.

Correct Answer: B

Rationale: The correct answer is B: Skeletal muscle. Skeletal muscle is voluntary as it is under conscious control, allowing us to move our body voluntarily. Cardiac muscle (A) is involuntary and found in the heart. Smooth muscle (C) is also involuntary and found in internal organs. Striated muscle (D) is a general term that can refer to both skeletal and cardiac muscle, but not all striated muscles are voluntary. Therefore, B is the correct answer as it specifically refers to the type of muscle tissue that is under voluntary control.

Correct Answer: B

Rationale: The correct answer is B: Support and protection. The skeletal system provides structural support for the body and protects internal organs. It also helps with movement, stores minerals, and produces blood cells. Choices A, C, and D are incorrect because the production of red blood cells occurs in the bone marrow, secretion of hormones is primarily the function of the endocrine system, and regulation of body temperature is controlled by the nervous system and other mechanisms, not the skeletal system.

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.

Correct Answer: A

Rationale: The correct answer is A: Left ventricle. The left ventricle is the largest and strongest chamber of the heart because it is responsible for pumping oxygen-rich blood to the entire body. It has thicker muscle walls compared to other chambers to generate enough force to push blood through the body's systemic circulation. The left atrium receives oxygenated blood from the lungs, but it does not pump blood out of the heart. The right ventricle pumps blood to the lungs for oxygenation and is not as strong as the left ventricle. The right atrium receives deoxygenated blood from the body and sends it to the right ventricle. Therefore, the left ventricle is the correct answer due to its crucial role in systemic circulation and its muscular structure.