which of the following structures regulates the transport of substances in and out of a cell
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HESI A2

HESI A2 Practice Test Anatomy and Physiology

1. Which of the following structures regulates the transport of substances in and out of a cell?

Correct answer: B

Rationale: The cell membrane, also known as the plasma membrane, is responsible for regulating the transport of substances in and out of the cell. It acts as a selective barrier, allowing the passage of certain molecules while restricting others. This selective permeability helps maintain homeostasis within the cell by controlling the movement of essential substances like nutrients and waste products. The nucleus (Choice A) is the organelle that houses the cell's genetic material and is not directly involved in regulating substance transport. Cytoplasm (Choice C) is the gel-like substance that fills the cell and does not play a direct role in regulating substance transport. Mitochondria (Choice D) are responsible for energy production in the cell through cellular respiration and are not primarily involved in substance transport.

2. The shoulder is _________ to the elbow.

Correct answer: B

Rationale: Proximal refers to a position closer to the point of attachment or origin. In this case, the shoulder is closer to the point of attachment to the body compared to the elbow, making it proximal to the elbow. 'Posterior' refers to the back side of the body, 'distal' means farther away from the point of attachment, and 'medial' refers to the middle of the body. These terms do not accurately describe the relationship between the shoulder and the elbow in this context.

3. What is the primary function of the hypothalamus?

Correct answer: A

Rationale: The primary function of the hypothalamus is to regulate body balance and thermoregulation. It plays a crucial role in maintaining overall body equilibrium by controlling functions such as body temperature and water balance. While the hypothalamus is also involved in hunger and thirst regulation, its main role is to ensure homeostasis by monitoring and adjusting body balance and temperature. Choices B, C, and D are incorrect because hunger and thirst regulation, sleep and circadian rhythm regulation, and control of voluntary movements are secondary functions of the hypothalamus compared to its primary role in maintaining body balance and thermoregulation.

4. What is the name of the structure that prevents food from entering the airway?

Correct answer: D

Rationale: The epiglottis is the structure that prevents food from entering the airway. It acts as a lid over the trachea during swallowing, directing food to the esophagus instead of the windpipe (trachea). The trachea (Choice A) is the windpipe that allows air to pass into the lungs, the esophagus (Choice B) is the tube that carries food from the mouth to the stomach, and the diaphragm (Choice C) is a muscle involved in breathing and not in preventing food passage.

5. Which organ system is primarily responsible for preventing water loss?

Correct answer: B

Rationale: The correct answer is B: The integumentary system. The integumentary system, which includes the skin, is primarily responsible for preventing water loss from the body. The skin acts as a barrier that helps regulate moisture and prevent excessive water loss through a process known as transepidermal water loss. The nervous system (choice A) is responsible for transmitting signals throughout the body, the lymphatic system (choice C) is responsible for the immune response and fluid balance, and the urinary system (choice D) is responsible for filtering blood and producing urine, but they do not primarily prevent water loss like the integumentary system.

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