The lungs move easily within their protective sacs due to

Correct Answer: A

Rationale: The correct answer is A: intrapleural fluid. Intrapleural fluid reduces friction between the lungs and the chest wall, allowing them to move easily during breathing. This fluid creates a lubricated surface that facilitates smooth movement. Leaking plasma (B) and mucus (D) do not provide the necessary lubrication for lung movement. Blood (C) plays a role in oxygen exchange but does not directly contribute to the ease of lung movement within the pleural sacs.

Correct Answer: D

Rationale: The correct answer is D: expiratory reserve volume. After normal exhalation (tidal volume), the expiratory reserve volume represents the additional volume of air that can be forcefully exhaled. This volume is used during activities requiring increased breathing effort. Choices A and C are incorrect because tidal volume is the volume of air inhaled or exhaled during normal breathing, and inspiratory reserve volume is the extra volume of air that can be inhaled after a normal inhalation. Choice B, residual volume, is the volume of air remaining in the lungs after maximal exhalation and cannot be exhaled voluntarily.

Correct Answer: C

Rationale: The correct answer is C: 500 ml. Tidal volume refers to the amount of air inspired or expired during normal breathing. In adult humans, the average tidal volume is around 500 ml. This volume represents the typical amount of air exchanged with each breath. Choices A, B, and D are incorrect because they do not accurately reflect the standard tidal volume in human beings. Option A (1000 ml) and B (1500 ml) are too high for a normal tidal volume, while option D (4.5 ml) is too low. Therefore, the correct answer is C as it aligns with the average tidal volume in human beings.

Correct Answer: D

Rationale: The correct answer is D: Spasm in bronchial muscles. Asthma is a chronic respiratory condition characterized by inflammation and narrowing of the airways, leading to difficulty breathing. Bronchial muscles in the airways undergo spasms, causing constriction and making it hard to breathe. Infection of the trachea (A) or lungs (B) may lead to respiratory symptoms but is not the primary cause of asthma. Bleeding into the pleural cavity (C) is unrelated to the pathophysiology of asthma. Therefore, the correct answer is D as it directly correlates with the underlying mechanism of asthma.

Correct Answer: C

Rationale: The correct answer is C. Tying a square knot at the back of the neck is incorrect because it can be too tight and cause discomfort or restrict airflow. A is correct as holding the device securely is necessary for safety. B is correct as suctioning before changing ties prevents aspiration. D is correct as using half-strength peroxide is appropriate for cleaning. Tying a square knot can lead to complications, making it the action that requires intervention.