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(trā`kēə) or


principal tube that carries air to and from the lungs. It is about 4 1-2 in. (11.4 cm) long and about 3-4 in. (1.9 cm) in diameter in the adult. It extends from the larynxlarynx
, organ of voice in mammals. Commonly known as the voice box, the larynx is a tubular chamber about 2 in. (5 cm) high, consisting of walls of cartilage bound by ligaments and membranes, and moved by muscles. The human larynx extends from the trachea, or windpipe.
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 to the bronchial tubes and is situated in front of the esophagus (see respirationrespiration,
process by which an organism exchanges gases with its environment. The term now refers to the overall process by which oxygen is abstracted from air and is transported to the cells for the oxidation of organic molecules while carbon dioxide (CO2
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). The trachea consists of a supporting layer of connective and muscular tissue in which are embedded from 16 to 20 U-shaped rings of hard cartilage that encircle the front of the tube. Tiny hairs, or cilia, in the mucous membrane lining keep dust and other foreign particles from entering the lungs. The foreign material becomes trapped in the mucus and is swept by the beating cilia to the nose or mouth, where it is discharged from the body. The air tubes of insects and other arthropods are also called trachea.



an organ of the respiratory tract in vertebrates, including man, that is situated between the larynx and bronchi.

In amphibians, the trachea is not divided into bronchi, as the lungs start at the trachea. Nor is it separate from the larynx in all species; for example, it is absent in tailless amphibians, where the lungs start at the trachea. In tailed amphibians, the trachea is usually long and has paired cartilages that sometimes grow together.

In reptiles, birds, and mammals, the trachea is distinctly separate from the larynx and is divided into bronchi. The length of the trachea is directly proportional to the length of the neck and inversely proportional to the length of the bronchi. The trachea in reptiles consists of closed or horseshoe-shaped cartilaginous rings, while in birds it usually consists of closed, partially ossified rings, which in some species form numerous windings and widenings that together reverberate sound. In many birds, the lower rings form the syrinx.

In mammals, the trachea consists of cartilaginous half-rings; closed rings are found in beavers, agoutis, flying lemurs, and representatives of the genus Lemur. The dorsal side of the trachea is usually membranous and contiguous with the esophagus. In whales and Sirenia, the cartilages partly fuse together to form a type of spiral. The trachea is usually divided into two bronchi in the thorax. A supplementary bronchus usually branches off the trachea in toothed whales, ruminants, and swine.

The human trachea or windpipe is a direct continuation of the larynx. It is a tube 11–13 cm long, consisting of 16–20 cartilaginous half-rings that are joined by fibrous connective tissue. It is lined with a mucous membrane. The submucous layer contains many mixed mucous glands. Inflammation of the tracheal mucosa is called tracheitis.



(1) A respiratory organ of terrestrial arthropods in the form of an air-conveying tubule that threads through the body and opens at the body surface, forming a spiracle or stigma.

Tracheae are deep invaginations in the body surface and are lined with a thin layer of chitin, which forms a supportive spiral filament that prevents collapse of the tubule walls. In insects and solpugids, extremely slender branchings of the tracheae, tracheoles, thread through the entire body, entwining the organs and even penetrating the interiors of some cells. Thus, oxygen is delivered directly to the site where it is required, and gases are exchanged without the help of a circulatory system.

Many arthropods with highly developed tracheal systems make respiratory movements, such as rhythmic contractions and expansions of the abdomen. In more primitive myriapods and insects, almost all segments of the body have a pair of tracheal bundles and stigmata. In centipedes and most insects, bundles of tracheae that are at first independent later unite as larger longitudinal bundles to form a single respiratory system, and some segments lack stigmata. Many arachnids breathe by means of tracheae, for example, solpugids, phalangids, pseudoscorpions, and many spiders, ticks, and mites. The tracheae and stigmata of these arachnids are located in various parts of the body and are developed independently in the evolutionary process, so that they are not homologous. The tracheae of terrestrial arthropods of other classes also originated independently. In the Onycho-phora, primitive tracheae are represented by numerous bundles of extremely slender tubules, which open into a common stigma; the stigmata are distributed in more or less disorderly fashion throughout the entire body. Some oniscoideans have rudimentary tracheae in the form of tubular branched invaginations on the surfaces of the exopodites of the anterior abdominal legs.

(2) In plants, water-conveying vessels of the xylem.


Dogel’, V. A. Sravnitel’naia anatomiia bespozvonochnykh, part 1. Leningrad, 1938. Pages 411–35.
Beklemishev, V. N. Osnovy sravnitel’noi anatomii bespozvonochnykh, 3rd ed., vol. 2. Moscow, 1964. Pages 54–60.



The cartilaginous and membranous tube by which air passes to and from the lungs in humans and many vertebrates.
A xylem vessel resembling the trachea of vertebrates.
(invertebrate zoology)
One of the anastomosing air-conveying tubules composing the respiratory system in most insects.


1. Anatomy Zoology the membranous tube with cartilaginous rings that conveys inhaled air from the larynx to the bronchi
2. any of the tubes in insects and related animals that convey air from the spiracles to the tissues
3. Botany another name for vessel
References in periodicals archive ?
The structures that make up the posterior respiratory system of boto and tucuxi were evaluated macroscopically at the UFAC's Laboratory of Animal Anatomy (Center for Biological and Nature Sciences) and the following biometric parameters were taken: length, width and thickness of the components of the trachea, tracheal bronchus, main bronchi and lungs.
After the macroscopic analysis, fragments of the trachea, tracheal bronchus, main and secondary bronchi, and lungs were removed from the parietal and mediastinal surfaces in their cranial, middle and caudal regions.
0 cm-long fragments of the cranial and caudal portions of the trachea, tracheal bronchus, main bronchi and lungs, washed in distilled water for 20 min and post-fixed in 1 % osmium tetroxide solution (Polyscience[R], Inc.
The artificial trachea was anastomosed without tension, kink, or rotation.
A reverse "L" shape skin incision was made, the trachea was transected below the tumor, and a tracheal tube was inserted into the distal trachea to maintain ventilation and anesthesia.
9-mm rigid telescope with integrated sheath (Karl Storz Veterinary Endoscopy, Goleta, CA, USA) and revealed at least 3 strictures spanning the distal one-third of the trachea (Fig 2).
Because of expected postoperative inflammation of the trachea and the need to provide intratracheal medication, the air sac cannula was replaced before anesthetic recovery.
Twenty rats were anesthetized by intraperitoneal administration of pentobarbital (60 mg/kg), and two pieces of trachea about 5 mm in length were removed from each rat.
Electrical field stimulation (EFS; 5 Hz, 5-ms pulse duration, at a voltage range of 30-90 V, trains of stimulation for 5 s) was applied to the trachea strip with two wire electrodes placed parallel to the trachea strip and connected to a direct-current stimulator (Grass S44; Grass Instrument Co.
This was the first regenerated trachea transplant surgery using a scaffold manufactured by HART and the implant used in the procedure was grown in one of HART's "InBreath" bioreactors.
Because the cells used to regenerate the trachea were the patient's own, there has been no rejection of the transplant and the patient is not taking immunosuppressive drugs.
It was progressing and almost completely blocked the trachea.