Biology · Breathing and Exchange of Gases · NEET
No. The trachea is the single main windpipe in the neck and upper chest. It runs down to the mid-thorax level and then splits into two primary bronchi. So the trachea comes first (one tube), and the bronchi come after it (two tubes). NCERT lists them as separate parts of the conducting tract.
Two. The trachea divides into a right primary bronchus and a left primary bronchus, one going to each lung. This is a very common NEET point: one trachea, two primary bronchi.
Bronchi are the larger branches (primary, secondary, tertiary) and their walls are held open by cartilage. Bronchioles are the smallest branches that come after the tertiary bronchi; they have very thin walls with no cartilage. Bronchi carry air toward the alveoli; the terminal bronchioles open into the alveoli where gas exchange happens.
NCERT does not stress this, but it is a common textbook add-on: the right primary bronchus is shorter, wider and more vertical than the left. For NEET, focus mainly on the branching order and that there are two primary bronchi; treat the wider-right point as extra reading, not a core NCERT fact.
No. The trachea and bronchi are supported by cartilage (incomplete C-shaped rings in the trachea) to stop them from collapsing. The fine bronchioles have no cartilage in their walls. This is why bronchioles can narrow during asthma — there is no cartilage to hold them open.
The trachea, bronchi and bronchioles are lined by ciliated epithelium (with mucus-secreting cells). The cilia beat to move dust and mucus back up and out, cleaning the air before it reaches the alveoli. NEET matching questions repeatedly pair 'bronchiole → ciliated epithelium'.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Larynx → trachea → primary bronchi → secondary bronchi → tertiary bronchi → bronchioles → terminal bronchioles → alveoli. Remember each step gets narrower and more numerous.
They are part of the conducting part of the respiratory system. The conducting part carries, cleans, warms and moistens air but does not exchange gases. Only the alveoli (respiratory part) exchange gases.
Incomplete cartilaginous rings (C-shaped) support the trachea and keep the airway open. The gap in the ring faces the food pipe (oesophagus) behind it, allowing food to pass. This links directly to the next concept: why airways have incomplete cartilage rings.
Most bronchioles are conducting (no exchange). Only after the terminal bronchioles, where the alveoli begin, does gas exchange occur. For NEET, treat bronchioles as conducting unless the question specifically mentions the alveolar region.
