Carina
Main bronchi · Sternal angle T4/5 Vagal afferents
The sagittal cartilaginous keel at the tracheal bifurcation, at the level of the sternal angle (T4/5) at rest and lying just to the left of the midline, so that the right main bronchus is the straighter continuation of the trachea. Its mucosa is the most sensitive cough-receptor zone in the airway.
Traced from the start
- Trachea
- Carina
Detail
- Level
- Sternal angle, T4/T5 disc, in the cadaver and at end-expiration; moves down to T6 in deep inspiration or standing
- Position
- Slightly left of the midline, which adds to the rightward bias of inhaled material
- Relations
- Subcarinal (station 7) lymph nodes immediately below; left atrium below and in front; oesophagus behind; aortic arch to the left, azygos arch to the right
- Innervation
- Vagal afferents; the most sensitive site for triggering the cough reflex
- Subcarinal angle
- About 60 to 75 degrees with a wide normal range; above 90 to 100 degrees is abnormal
When it goes wrong
Left atrial enlargement (mitral stenosis)
Carina splayed with the left main bronchus lifted; subcarinal angle above 90 to 100 degrees on the chest film, with a double right heart border
Subcarinal lymphadenopathy (lung cancer, lymphoma, sarcoidosis, tuberculosis)
Widened, blunted and fixed carina at bronchoscopy; loss of the sharp keel is a sign of nodal spread
Endotracheal tube tip resting on the carina
Violent coughing and bronchospasm; the tip should sit 3 to 5 cm above the carina, mid-trachea at about T2 to T4 on the chest film
Practise this structure
3 questions in the bank tagged Surface Anatomy.
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