Transverse section of the trachea, just above its bifurcation, with a bird’s-eye view of the interior. (Carina not labeled; the ridge that separates the left and right bronchus.)
The carina of trachea (also: "tracheal carina"[1]) is a ridge[1] of
cartilage[2] at the base of the
trachea separating the openings of the left and right
main bronchi.[1][2]
Structure
The carina is a cartilaginous ridge separating the left and right main bronchi that is formed by the inferior-ward and posterior-ward prolongation of the inferior-most
tracheal cartilage.[2]
The carina occurs at the lower end of the trachea - usually at the level of the 4th to 5th
thoracic vertebra.[3][4] This is in line with the
sternal angle, but the carina may raise or descend up to two vertebrae higher or lower with
breathing. The carina lies to the left of the midline, and runs antero-posteriorly (front to back).[citation needed]
The carina is around the area posterior to where the
aortic arch crosses to the left of the trachea.[4] The
azygos vein crosses right to the trachea above the carina.[6]
Physiology
The mucous membrane of the carina is the most sensitive area of the trachea and larynx for triggering a cough reflex.[citation needed]
Clinical significance
Tracheobronchial injury, an injury to the airways, occurs within 2.5 cm of the carina 60% of the time.[7]
Diagnostic radiology
Widening and distortion of the carina is a serious radiological sign that usually indicates
carcinoma of the
lymph nodes around the region where the trachea divides.[citation needed]
Additional images
Anatomical dissection of trachea and main bronchi showing the carina