Vertebrate trachea
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| Vertebrate trachea | |
|---|---|
| Conducting passages. | |
| Laryngoscopic view of interior of larynx. (Trachea labeled at bottom.) | |
| Gray's | subject #237 1084 |
| Artery | tracheal branches of inferior thyroid artery |
| MeSH | Trachea |
The trachea, or windpipe, is a tube that connects to the pharynx or larynx, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosal 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.
Contents |
In humans
The trachea has an inner diameter of about 20 to 25 millimetres (0.79 to 0.98 in) and a length of about 10 to 16 centimetres (3.9 to 6.3 in). It commences at the larynx, level with the fifth cervical vertebra, and bifurcates into the primary bronchi at the vertebral level of T4/T5.
There are about fifteen to twenty incomplete C-shaped cartilaginous rings which reinforce the anterior and lateral sides of the trachea to protect and maintain the airway. 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.
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)
In 2008, a Colombian woman received a trachea transplant using her own stem cells so her body would not reject the transplant.[1]
In other animals
Allowing for variations in the length of the neck, the trachea in other mammals is generally similar to that in humans. The reptilian trachea is also generally similar.[2]
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.[2]
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.[2]
The only vertebrate to have lungs, but no trachea, is Polypterus, in which the lungs arise directly from the pharynx.[2]
Additional images
Gray384.png Section of the neck at about the level of the sixth cervical vertebra. | Gray490.png Front view of heart and lungs. | Gray622.png The tracheobronchial lymph glands. | Gray952.png Ligaments of the larynx. Posterior view. |
Gray954.png Coronal section of larynx and upper part of trachea. | Gray958.png Muscles of larynx. Posterior view. | Gray959.png Muscles of larynx. Side view. Right lamina of thyroid cartilage removed. | Gray964.png Transverse section of trachea. |
Gray994.png Sagittal section of nose mouth, pharynx, and larynx. | Gray1032.png The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind. | Illu08 thyroid.jpg Thyroid | Respiratory system.svg Respiratory system |
Trachea.JPG Microscopic cross section of human trachea. |
References
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