which muscle is responsible for breathing

HESI A2

Anatomy HESI A2 Practice Test

1. Which muscle is responsible for breathing?

A. Diaphragm
B. Intercostal muscles
C. Rectus abdominis
D. Pectoralis major

Correct answer: A

Rationale: The diaphragm is the primary muscle responsible for breathing. It is a large, dome-shaped muscle located at the base of the chest cavity. When it contracts, it flattens, increasing the volume of the chest cavity and causing inhalation. When it relaxes, it returns to its dome shape, decreasing the volume of the chest cavity and causing exhalation. The intercostal muscles, located between the ribs, assist the diaphragm in breathing by expanding and contracting the chest cavity. The rectus abdominis and pectoralis major are not directly involved in the process of breathing.

2. What is the primary role of the liver in the body?

A. Producing insulin
B. Detoxifying harmful substances
C. Digesting food
D. Storing energy

Correct answer: B

Rationale: The correct answer is B: Detoxifying harmful substances. While the liver does produce bile for digestion and stores nutrients like glycogen, its primary function is to filter and detoxify blood coming from the digestive tract before passing it to the rest of the body. Therefore, choices A, C, and D are incorrect. Producing insulin is mainly done by the pancreas, digesting food is primarily the role of the stomach and intestines, and storing energy is a function of various organs like muscles and fat cells.

3. What is the primary function of platelets?

A. To fight infections
B. To clot blood
C. To carry oxygen
D. To transport nutrients

Correct answer: B

Rationale: The primary function of platelets, or thrombocytes, is to clot blood. Platelets play a crucial role in hemostasis by forming clots to prevent excessive bleeding when injuries occur. They are not directly involved in fighting infections, carrying oxygen, or transporting nutrients. Therefore, the correct answer is B.

4. Through which organ do muscles push food into the stomach via peristalsis?

A. Mouth
B. Small intestine
C. Epiglottis
D. Esophagus

Correct answer: D

Rationale: The correct answer is D, Esophagus. Muscles push food into the stomach via peristalsis in the esophagus. Peristalsis is a coordinated muscular contraction that helps move food from the mouth to the stomach through the esophagus. The rhythmic contractions of the esophageal muscles create a wave-like motion that propels food downward toward the stomach for digestion. Choices A, B, and C are incorrect because the mouth is where digestion begins but does not push food into the stomach, the small intestine is mainly responsible for absorbing nutrients, and the epiglottis is a flap that prevents food from entering the trachea during swallowing, not involved in pushing food into the stomach.

5. Which part of the brain is responsible for regulating emotions and memory?

A. Cerebrum
B. Cerebellum
C. Amygdala
D. Brainstem

Correct answer: C

Rationale: The amygdala, located in the temporal lobe of the brain, is responsible for regulating emotions and memory, particularly those related to fear and pleasure. It plays a crucial role in processing emotional responses, forming emotional memories, and modulating emotional reactions. The cerebrum (Choice A) is responsible for higher brain functions such as thought and action. The cerebellum (Choice B) is mainly involved in coordination and balance. The brainstem (Choice D) controls basic life functions such as breathing and heart rate.