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|Laryngoscopic view of interior of larynx. (Trachea labeled at bottom.)|
|Gray's||subject #237 1084|
|Artery||tracheal branches of inferior thyroid artery|
|Vein||brachiocephalic vein, azygos vein accessory hemiazygos vein|
In tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx and larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles that the cilia then waft upward toward the larynx and then the pharynx where it can be either swallowed into the stomach or expelled as phlegm.
In non-humans 
In birds, the trachea runs from the pharynx to the syrinx, from which the primary bronchi diverge. Swans have an unusually elongated trachea, part of which is coiled beneath the sternum; this may act as a resonator to amplify sound. In some birds, the cartilagenous rings are complete, and may even be ossified.
In amphibians, the trachea is normally extremely short, and leads directly into the lungs, without clear primary bronchi. A longer trachea is, however, found in some long-necked salamanders, and in caecilians. While there are irregular cartilagenous nodules on the amphibian trachea, these do not form the rings found in amniotes.
In humans 
The trachea has an inner diameter of about 25 millimetres (1.0 in) and a length of about 10 to 16 centimetres (4 to 6 in). It commences at the lower border of the larynx, level with the sixth cervical vertebra, and bifurcates into the primary bronchi at the vertebral level of thoracic vertebra T5, or up to two vertebrae lower or higher, depending on breathing.
There are about fifteen to twenty incomplete C-shaped cartilaginous rings that reinforce the anterior and lateral sides of the trachea to protect and maintain the airway, leaving a membranous wall (pars membranacea) dorsally without cartilage. The trachealis muscle connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen of the trachea to increase the air flow rate. The esophagus lies posteriorly to the trachea. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus. A flap-like epiglottis closes the opening to the larynx during swallowing to prevent swallowed matter from entering the trachea. Lined with respiratory epithelium.
Tracheal diseases and conditions 
The following are diseases and conditions that affect the trachea:
- Tracheal agenesis, a rare birth defect in which the trachea fails to develop. The defect is normally fatal.
- Tracheotomy, a surgical procedure on the neck to open a direct airway through an incision in the trachea
- Tracheomalacia (weakening of the tracheal cartilage)
- Tracheal collapse (in dogs)
- Tracheobronchial injury (perforation of the trachea or bronchi)
- Mounier-Kuhn syndrome (causes abnormal enlargement of the trachea)
In 2008, a Colombian woman received a trachea transplant using her own stem cells so her body would not reject the transplant. In June 2011, a team of surgeons led by Professor Paolo Macchiarini at the Karolinska University Hospital performed the first synthetic windpipe transplant on a 36-year-old Eritrean man, Andemariam Teklesenbet Beyene.
Additional images 
See also 
- Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 336–337. ISBN 0-03-910284-X.
- "The top health stories of 2008 - CNN.com". CNN. 2008-12-26. Retrieved 2010-05-27.
- "Surgeons carry out first synthetic windpipe transplant". BBC News. 2011-07-07. Retrieved 2011-07-07.
- First Successful Transplantation of a Synthetic Tissue Engineered Windpipe. Karolinska University Hospital website, retrieved 8/7/2011.