One of the following is not a function of the human respiratory system?

Appeared in: ISRO 2024

Explanation

The respiratory system's primary role in air conditioning is to bring inspired air to body temperature, which almost always involves warming, not cooling.
While some heat loss can occur via respiration as part of the body's overall thermoregulation, actively cooling incoming air is not a designated physiological function of the respiratory tract.
The anatomical structures of the upper airway, particularly the nasal passages, are specifically adapted to warm, filter, and humidify air.

Option A: This is a primary function. The mucous membranes of the upper respiratory tract add moisture to the inspired air.
Option C: This is a primary function. The rich vascular network in the nasal cavity efficiently warms incoming air to protect the lower airways.
Option D: This is the most vital function of the respiratory system, where oxygen is supplied to the blood and carbon dioxide is removed.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of the human respiratory system as background academic context rather than a clinical decision trigger.
Understanding the air conditioning function is crucial for patients on mechanical ventilation. The ventilator circuit must artificially warm and humidify the air to prevent airway damage, as the upper airway is bypassed.
What if? If a patient has a tracheostomy, they breathe air that bypasses the nasal passages. This air is cooler and drier, increasing the risk of thick mucus plugs, infection, and airway irritation, which necessitates artificial humidification (e.g., a heat and moisture exchanger or HME).

How to Approach the Question

Identify the negative keyword 'not' in the question stem. This means you are looking for the option that is an exception or incorrect statement.
Recall the main functions of the respiratory system: gas exchange, air filtration, warming inspired air, and humidifying inspired air.
Systematically evaluate each option against your knowledge.
Option A (Humidifies), Option C (Warms), and Option D (Exchange of gases) are all well-known, primary functions.
Option B (Cools the air) is not a standard function. The system's goal is to bring air to body temperature, which typically involves warming. Therefore, this is the correct answer.

Concept Tested & Keywords

Q1JtarkjYyQIB0hUT161J3

E6 Physiology Guyton 4SAE Part 2A p. 42-44

E6 Nursing Vital Signs p. 61-63

Practise the full ISRO 2024

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