Vertebrate trachea

The traceartes, or windpipe, is a tube that has an inner diameter of about 20-25 mm and a length of about 10-16 cm in humans. It commences at the larynx (at the vertebral level of C6 in humans) and bifurcates into the primary (main) bronchi (at the vertebral level of T4/T5 in humans) in mammals, and from the pharynx to the syrinx in birds, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosae goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards towards their larynx and then the pharynx where it can either be swallowed into the stomach or expelled as phlegm.

In humans there are about 15 – 20 incomplete C-shaped cartilaginous rings which reinforce the anterior and lateral sides of the trachea to protect and maintain the airway open. There is a piece of smooth muscle connecting the ends off the incomplete cartilaginous rings called the Trachealis muscle. This contracts reducing the size of the lumen of the trachea to increase the air flow rate during coughing. The esophagus lies posteriorly to the trachea. The cartilaginous rings are incomplete because this allows the trachea to collapse slightly to allow food to pass down the esophagus. The epiglottis is the flap that closes the trachea during swallowing to prevent swallowed matter from entering the trachea.

In 2008, a Colombian woman received a trachea transplant using her own stem cells so her body would not reject the transplant.

Tracheal diseases and conditions
The following are diseases and conditions that affect the trachea:


 * Choking
 * 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)