In which part of the respiratory system gaseous exchange takes place?

Appeared in: NVS- 2025

Explanation

Alveoli are the primary sites for gas exchange in the lungs, where oxygen enters the blood and carbon dioxide is removed.
They are tiny, thin-walled air sacs located at the end of the respiratory tree, collectively forming the respiratory zone.
The alveolar and capillary walls form a very thin structure called the respiratory membrane, which facilitates rapid and efficient diffusion of gases.

Option A: The larynx, or voice box, is part of the conducting zone. Its main functions are air conduction and phonation (sound production), not gas exchange.
Option B: Secondary bronchi are part of the conducting zone, responsible for distributing air to the different lobes of the lungs. Their walls are too thick and contain cartilage, preventing any gas exchange.
Option D: The pharynx, or throat, is a common passageway for air and food. It is part of the upper respiratory tract's conducting zone and is not involved in gas exchange.

Clinical Relevance

Nursing practice connection: Knowing Primary site of gas exchange in the respiratory system helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding that gas exchange occurs in the alveoli is fundamental for nurses to grasp the pathophysiology of diseases like pneumonia, emphysema, and ARDS, which directly damage this area and impair oxygenation.
A nurse's respiratory assessment, including listening for crackles (fluid in alveoli) and monitoring oxygen saturation (SpO₂), directly relates to the efficiency of gas exchange at the alveolar level.
What if? If a patient develops pulmonary edema, fluid leaks into the interstitial space and alveoli. This increases the thickness of the respiratory membrane, severely impairing gas diffusion and causing hypoxemia, even if the patient is breathing.

How to Approach the Question

First, identify the key physiological process in the question, which is 'gaseous exchange'.
Mentally divide the respiratory system into its two main functional parts: the conducting zone (for air transport) and the respiratory zone (for gas exchange).
Evaluate each option based on its primary function. The pharynx, larynx, and bronchi are all structures designed to conduct air.
Recognize that the alveoli are the terminal structures specifically adapted with extremely thin walls and a rich capillary network for the sole purpose of gas exchange.
Conclude that the alveoli are the only structures listed that belong to the respiratory zone and are the correct answer.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2A p. 38-39

E6 Nursing Vital Signs p. 62-64

Practise the full NVS- 2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.