Anatomy HESI A2 Practice Test

Correct Answer: C

Rationale: Platelets play a crucial role in blood clotting, known as hemostasis. Step 1: When a blood vessel is damaged, platelets adhere to the site to form a temporary plug. Step 2: Platelets release chemicals that attract more platelets and help in clot formation. Step 3: This clotting process prevents excessive bleeding. Choice A is incorrect as oxygen is primarily carried by red blood cells. Choice B is incorrect as fighting infections is mainly done by white blood cells. Choice D is incorrect as nutrient transport is mainly carried out by the plasma in the blood.

Correct Answer: B

Rationale: The correct answer is B: Adrenal cortex. During stress, the adrenal cortex secretes cortisol and aldosterone, which help the body respond to stress. The parathyroid gland (A) regulates calcium levels, not stress hormones. The posterior pituitary gland (C) releases hormones like oxytocin and vasopressin, not stress hormones. The hypothalamus (D) plays a role in regulating the stress response by signaling the adrenal cortex to release stress hormones.

Correct Answer: B

Rationale: The correct answer is B: Mouth. Digestion begins in the mouth where food is mechanically broken down by chewing and chemically broken down by enzymes in saliva. This initial process prepares food for further digestion in the stomach and small intestine. The stomach (A) primarily functions to further break down food through acid and enzymes. The small intestine (C) is where the majority of nutrients are absorbed, not where digestion begins. The esophagus (D) is responsible for transporting food from the mouth to the stomach, but it does not participate in the actual digestion process.

Correct Answer: A

Rationale: The correct answer is A: Diaphragm. The diaphragm is the primary muscle responsible for breathing as it contracts and moves downward during inhalation, creating more space in the chest cavity for the lungs to expand. The intercostal muscles assist in expanding and contracting the ribcage during breathing, but they are not the primary muscle responsible. The rectus abdominis is involved in core stabilization and movement but not in the breathing process. The pectoralis major is a chest muscle that aids in arm movements but is not directly involved in the breathing mechanism. Therefore, the diaphragm is the correct answer as it plays a crucial role in the breathing process.

Correct Answer: C

Rationale: The primary function of hemoglobin in red blood cells is to carry oxygen. Hemoglobin binds to oxygen in the lungs and releases it to tissues throughout the body. This process is essential for cellular respiration. Choice A is incorrect because hemoglobin does not transport nutrients. Choice B is incorrect because the function of fighting infections is carried out by the immune system, not hemoglobin. Choice D is incorrect because hemoglobin does not produce energy; it facilitates the transport of oxygen which is necessary for energy production in cells.