carina

The carina is the fork in the road at the bottom of the windpipe — the sharp internal ridge where the single trachea divides into the two main bronchi heading to the right and left lungs. Its name comes from the Latin for the keel of a boat, which the ridge resembles.

Lined with especially sensitive nerve endings, the carina is a powerful trigger for the cough reflex: when secretions or a foreign object touch it, a forceful cough is set off to clear the airway. Its precise location and shape are landmarks seen during bronchoscopy.

Clinically the carina matters for safe airway management. A breathing tube should sit above the carina, not slip down one bronchus, and a widened or distorted carina on imaging can hint at enlarged lymph nodes or tumour spread between the lungs.