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In anatomy, the carina or tracheal bifurcation is a ridge of
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...
in the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
that occurs between the division of the two main bronchi.


Structure

The carina occurs at the lower end of the trachea (usually at the level of the 4th to 5th thoracic vertebra). This is in line with the
sternal angle The sternal angle (also known as the angle of Louis, angle of Ludovic or manubriosternal junction) is the synarthrotic joint formed by the articulation of the manubrium and the body of the sternum. The sternal angle is a palpable clinical landma ...
, but the carina may raise or descend up to two vertebrae higher or lower with
breathing Breathing (or ventilation) is the process of moving air into and from the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen. All aerobic creatures need oxygen for cellu ...
. The carina lies to the left of the midline, and runs antero-posteriorly (front to back). The
bronchial arteries In human anatomy, the bronchial arteries supply the lungs with nutrition and oxygenated blood. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung and are a vital part ...
supply the carina and the rest of the lower trachea. The carina is around the area posterior to where the
aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...
crosses to the left of the trachea. The
azygos vein The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blo ...
crosses right to the trachea above the carina.


Clinical significance

Foreign bodies that fall down the trachea are more likely to enter the right bronchus. The mucous membrane of the carina is the most sensitive area of the trachea and larynx for triggering a cough reflex. Widening and distortion of the carina is a serious sign because it usually indicates
carcinoma Carcinoma is a malignancy that develops from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesoderm ...
of the
lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that includ ...
s around the region where the trachea divides.
Tracheobronchial injury Tracheobronchial injury is damage to the tracheobronchial tree (the airway structure involving the trachea and bronchi). It can result from blunt or penetrating trauma to the neck or chest, inhalation of harmful fumes or smoke, or aspiration of ...
, an injury to the airways, occurs within 2.5 cm of the carina 60% of the time.


Additional images

File:Primary bronchi cross-sectional posterior view.PNG, Anatomical dissection of trachea and main bronchi showing the carina File:Blausen 0865 TracheaAnatomy.png, Anatomy of the trachea


References


External links

* - "Cast of trachea and bronchi, anterior view" (#2)
"Trachea and carina — tomogram, coronal plane" at SUNY Downstate Medical Center

Carina tracheae
entry in the public domain NCI Dictionary of Cancer Terms {{Authority control Trachea