Biology · Breathing and Exchange of Gases · NEET
| Extent / structures | External nostrils to terminal bronchioles (nasal chamber, pharynx, larynx, trachea, bronchi, bronchioles) | Alveoli and their alveolar ducts |
| Main function | Transports air; cleans, humidifies and warms it | Actual diffusion (exchange) of O2 and CO2 |
| Gas exchange | No gas exchange | Yes, site of gas exchange |
| Wall thickness | Thick walls (with cartilage in larger tubes) | Very thin walls for easy diffusion |
| Boundary marker | Ends at terminal bronchiole | Begins after terminal bronchiole |
The conducting part starts at the external nostrils and ends at the terminal bronchioles. Right after the terminal bronchiole, the respiratory part begins with the alveoli and their alveolar ducts. So the terminal bronchiole is the last structure of the conducting part.
The trachea is part of the conducting part. So are the primary, secondary and tertiary bronchi, and all bronchioles down to the terminal bronchioles. None of them do gas exchange; they only move air.
No. The conducting part never exchanges O2 or CO2. Its walls are too thick for diffusion. Actual diffusion of O2 and CO2 happens only at the alveoli in the respiratory part. This exact idea is a favourite NEET trap.
NCERT gives three jobs: (1) it transports atmospheric air to the alveoli, (2) it clears the air of foreign particles, and (3) it humidifies the air and brings it to body temperature. Gas exchange is NOT one of its jobs.
Alveolar ducts belong to the respiratory (exchange) part. NCERT clearly says the alveoli and their ducts form the respiratory or exchange part, so the ducts go with the alveoli, not with the bronchioles.
Because it is the site of actual diffusion of O2 and CO2 between the blood and the air. The alveolar wall is extremely thin, so gases can cross easily. That is why alveoli + ducts are also called the exchange part.
Which of the following is not the function of the conducting part of the respiratory system?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The conducting part (nostrils to terminal bronchioles) only carries, cleans, humidifies and warms air. The respiratory part (alveoli + alveolar ducts) is where O2 and CO2 actually diffuse.
The terminal bronchiole. Everything from the nostrils up to and including the terminal bronchioles is conducting; the alveoli and ducts after it are respiratory.
No. Bronchioles, including terminal bronchioles, belong to the conducting part and do not exchange gases. Only alveoli do.
NCERT states the two parts and their exact boundary in one line, and NEET repeatedly tests it (e.g. NEET 2022 asked which is NOT a function of the conducting part). It is high-yield and low-effort.
