A patient with chronic lung disease is undergoing lung function testing. What test result denotes the volume of air inspired and expired with a normal breath?

Correct Answer: C

Rationale: The correct answer is C: Tidal volume. Tidal volume is the volume of air inspired and expired with a normal breath. It represents the normal breathing pattern without any additional effort. Total lung capacity (A) is the maximum amount of air the lungs can hold, Forced vital capacity (B) is the maximum amount of air exhaled forcefully after a maximal inspiration, and Residual volume (D) is the volume of air remaining in the lungs after a forced exhalation. Therefore, Tidal volume is the only choice that represents the volume of air inspired and expired during a normal breath.

Correct Answer: B

Rationale: During external respiration, carbon dioxide moves from the blood into the lungs. This is because the blood carries carbon dioxide from the body tissues to the lungs to be exhaled. In the lungs, carbon dioxide diffuses from the blood into the alveoli to be eliminated during exhalation. Choice A is incorrect because carbon dioxide does not move from the blood into the tissue cells during external respiration. Choice C is incorrect as carbon dioxide is exhaled into the atmosphere, not the other way around. Choice D is incorrect as carbon dioxide is produced in the tissue cells and needs to be transported back into the blood for removal in the lungs.

Correct Answer: D

Rationale: Gap junctions play a role in cell-to-cell communication but are not directly involved in gas exchange efficiency at the blood air barrier. A: High partial pressure differences drive gas exchange. B: Short distance minimizes diffusion time. C: Large surface area allows for more exchange. Therefore, D is the correct answer as it is not a contributing factor to gas exchange efficiency.

Correct Answer: B

Rationale: The correct answer is B because the apneustic centers of the pons provide stimulation to the inspiratory center in the medulla oblongata to promote inhalation. This is essential for regulating the breathing cycle. Choice A is incorrect as the apneustic centers do not inhibit the pneumotaxic and inspiratory centers. Choice C is incorrect as the apneustic centers do not directly monitor blood gas levels. Choice D is incorrect as the apneustic centers do not alter chemoreceptor sensitivity.

Correct Answer: C

Rationale: The primary muscles of inspiration are the diaphragm and external intercostal muscles. The diaphragm contracts and moves downward, increasing the volume of the thoracic cavity, while the external intercostal muscles lift and expand the rib cage. This creates a negative pressure in the lungs, allowing air to flow in. A: Internal intercostal muscles are involved in forced expiration, not inspiration. B: While the diaphragm is a primary muscle of inspiration, internal intercostal muscles are not. D: Rectus abdominis and transversus thoracis are primarily involved in expiration, not inspiration.