the axial skeletal system contains all of these except

HESI A2

HESI A2 Anatomy and Physiology Practice Test

1. Which of the following is not part of the axial skeletal system?

A. the skull
B. the ribs
C. the breastbone
D. the radius

Correct answer: D

Rationale: The correct answer is D, the radius. The axial skeleton comprises bones located along the central axis of the body. It includes the skull, ribs, breastbone (sternum), vertebrae, and sacrum. The radius, on the other hand, is a bone of the forearm, part of the appendicular skeleton. The appendicular skeleton consists of the bones of the limbs and their girdles, not the central axial bones.

2. Which vitamin is essential for bone health?

A. Vitamin A
B. Vitamin D
C. Vitamin C
D. Vitamin K

Correct answer: B

Rationale: Vitamin D is the correct answer. It is essential for bone health as it helps in the absorption of calcium, a crucial mineral for maintaining strong and healthy bones. Adequate levels of Vitamin D are necessary to prevent conditions like osteoporosis and ensure optimal bone development and strength. Choice A, Vitamin A, is important for vision and immune function, but it is not directly related to bone health. Choice C, Vitamin C, is essential for collagen synthesis and immune function, but it is not primarily responsible for bone health. Choice D, Vitamin K, plays a role in blood clotting and bone metabolism, but Vitamin D has a more direct impact on bone health through its role in calcium absorption.

3. What does the parathyroid hormone regulate?

A. Magnesium
B. Calcium
C. Calcitonin
D. Glucocorticoids

Correct answer: B

Rationale: The parathyroid hormone primarily regulates calcium levels in the blood. It acts to increase calcium levels by stimulating the release of calcium from bones, enhancing calcium reabsorption in the kidneys, and promoting the conversion of vitamin D to its active form, which aids in calcium absorption from the intestines. Therefore, the correct answer is B. Choices A, C, and D are incorrect because the parathyroid hormone does not play a significant role in the regulation of magnesium (Choice A), calcitonin (Choice C), or glucocorticoids (Choice D).

4. Which of the heart's four chambers is the largest and the strongest?

A. Right atrium
B. Left ventricle
C. Right ventricle
D. Left atrium

Correct answer: B

Rationale: The left ventricle is the largest and strongest chamber of the heart. It pumps oxygenated blood to the body, making it vital for systemic circulation. The right atrium receives deoxygenated blood from the body, the right ventricle pumps this blood to the lungs, and the left atrium receives oxygenated blood from the lungs.

5. Which part of the brain controls involuntary actions such as breathing and heart rate?

A. Cerebrum
B. Cerebellum
C. Medulla oblongata
D. Hypothalamus

Correct answer: C

Rationale: The medulla oblongata, located at the base of the brainstem, controls essential involuntary actions such as breathing, heart rate, and blood pressure. It plays a crucial role in maintaining vital functions necessary for survival. The cerebrum is responsible for voluntary actions, conscious thought, and sensory processing, making it an incorrect choice. The cerebellum primarily coordinates movement, balance, and posture, not involuntary actions like breathing and heart rate. The hypothalamus regulates body temperature, thirst, hunger, and controls the endocrine system, but it is not directly responsible for controlling breathing and heart rate.