carina of trachea
Meaning of carina of trachea: The fork in the airway, and the reason an inhaled object almost always ends up in the right lung rather than the left.
Definition of carina of trachea
The carina of the trachea is the ridge of cartilage at the point where the windpipe divides into the right and left main bronchi. Seen from above it forms a sharp keel running front to back, separating the two openings. It lies behind the upper part of the breastbone, level with the fourth or fifth vertebra of the chest.
Why do inhaled objects go right?
Because the two branches are not mirror images. The right main bronchus leaves the ridge at a shallower angle, is wider, and runs more nearly straight down, so gravity and airflow carry anything solid into it. A peanut, a tooth fragment or vomited material inhaled while lying flat therefore lands in the right lung far more often than the left. The same asymmetry catches out a breathing tube advanced too far: it slips past the ridge into the right bronchi, ventilating one lung while the other collapses. Checking that both sides move and sound equal after a tube is placed exists because of this single anatomical quirk.
| Feature | Right main bronchus | Left main bronchus |
|---|---|---|
| Angle at the ridge | Shallower, nearer vertical | More horizontal |
| Width | Wider | Narrower |
| Length before it branches | Shorter | Longer |
| Inhaled material | Usually lands here | Reached less often |
Why does touching it provoke coughing?
The lining here is the most sensitive point in the whole airway. Nerve endings sitting in the ridge feed straight into the vagus nerve, and their job is to detect anything that has come too far down and expel it before it reaches the lungs. Stimulating this spot during bronchoscopy or suctioning produces a violent cough almost immediately, and drugs used for sedation blunt this reflex, which is part of why airway protection is lost under deep sedation. The reflex is also what makes choking on a crumb feel so instantly urgent.
What does a changed appearance mean?
Normally the ridge is thin, sharp and moves slightly with each breath. Lymph nodes draining both lungs sit directly beneath it, and when they enlarge they push the two bronchi apart, blunting and widening the ridge. That finding is followed up because it points at disease in the chest rather than in the airway wall itself. A ridge that has become rigid, broad and distorted suggests tumor growing into the wall from below. The same structure is described under the name tracheal carina, and its position marks where the trachea ends.
Also known as
Used in a sentence
Bronchoscopy showed a sharp carina of the trachea with normal main bronchi.
Good to know
The right main bronchus leaves the carina at a shallower angle and is wider than the left, so inhaled material and a breathing tube advanced too far both tend to enter the right lung, leaving the left underventilated.
Word origin
Where “carina of trachea” comes from
Latin carina, the keel of a ship, describes the shape of the ridge; trachea comes from the Greek tracheia arteria, the rough artery.