Trachea

Trachea
Illu conducting passages.svg
Conducting passages.
Details
Arterytracheal branches of inferior thyroid artery
Veinbrachiocephalic vein, azygos vein accessory hemiazygos vein
Identifiers
LatinTrachea
D014132
A06.3.01.001
7394
Anatomical terminology

The trachea, colloquially called the windpipe, is a cartilaginous tube that connects the pharynx and larynx to the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea the cricoid cartilage attaches it to the larynx. This is the only complete tracheal ring, the others being incomplete rings of reinforcing cartilage. The trachealis muscle joins the ends of the rings and these are joined vertically by bands of fibrous connective tissue – the annular ligaments of trachea. The epiglottis closes the opening to the larynx during swallowing.

The trachea develops in the second month of development. It is lined with an epithelium that has goblet cells which produce protective mucins (see Respiratory epithelium). An inflammatory condition, also involving the larynx and bronchi, called croup can result in a barking cough. A tracheotomy is often performed for ventilation in surgical operations where needed. Intubation is also carried out for the same reason by the inserting of a tube into the trachea. From 2008, operations have experimentally transplanted a windpipe grown by stem cells, and synthetic windpipes; however, a successful method for this method of transplant does not currently exist and development of such a method remains theoretically daunting.[1][2]

The word "trachea" is used to define a very different organ in invertebrates than in vertebrates. Insects have an open respiratory system made up of spiracles, tracheae, and tracheoles to transport metabolic gases to and from tissues.

Structure

Blausen 0865 TracheaAnatomy.png

An adult's trachea has an inner diameter of about 1.5 to 2 centimetres (0.6 to 0.8 in) and a length of about 10 to 11 centimetres (4 in.).[3] It begins at the bottom of the larynx, and ends at the carina, the point where the trachea branches into left and right main bronchi.[3] The trachea begins level with the sixth cervical vertebra and the carina is found at the level of the fifth thoracic vertebra (T5),[3] opposite the sternal angle and can be positioned up to two vertebrae lower or higher, depending on breathing.

The trachea is surrounded by rings of hyaline cartilage; these rings are incomplete and C-shaped. The cricoid cartilage is attached to the first tracheal ring at top of the trachea and acts as the bottom of the larynx. There are fifteen to twenty rings in total, separated by narrow intervals. These reinforce the front and sides of the trachea to protect and maintain the airway.[citation needed]

In front of the rings lies connective tissue and skin. Several other structures pass or sit over it; the jugular arch, which joins the two anterior jugular veins, sits in front of the upper part of the trachea. The sternohyoid and sternothyroid muscles stretch along its length, and the thyroid gland sits below this; with the isthmus of the gland overlying the second to fourth rings.[3]

The first tracheal ring is broader than the rest, and often divided at one end; it is connected by the cricotracheal ligament with the lower border of the cricoid cartilage, and is sometimes blended with the next cartilage down. The last cartilage is thick and broad in the middle, due to its lower border being prolonged into a triangular hook-shaped (uncinate) process, which curves downward and backward between the two bronchi. It ends on each side in an imperfect ring, which encloses the commencement of the bronchus. The cartilage above the last is somewhat broader than the others at its center.[citation needed]

Two or more of the cartilages often unite, partially or completely, and they are sometimes bifurcated at their extremities. The rings are generally highly elastic but they may calcify with age.

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 rate of air flow.[4] The esophagus lies posteriorly to the trachea, adjoining along the tracheoesophageal stripe. Circular horizontal bands of fibrous tissue called the annular ligaments of trachea join the tracheal rings together. 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.

Development

In the fourth week of development of the human embryo as the respiratory bud grows, the trachea separates from the foregut through the formation of tracheoesophageal ridges which fuse to form the tracheoesophageal septum and this separates the future trachea from the oesophagus and divides the foregut tube into the laryngotracheal tube. Before the end of the fifth week, the trachea begins to develop from the laryngotracheal tube which develops from the laryngotracheal groove. The first part of the cephalic region of the tube forms the larynx, and the next part forms the trachea.

The trachea is no more than 4mm diameter during the first year of life, expanding to its adult diameter by late childhood. The trachea is more mobile and of more variable length, deeper, and smaller in children.[3]

Histology

10 X Photograph of a histological sample of a human trachea coloured with H&E stain
Cross-section

The trachea is lined with a layer of pseudostratified ciliated columnar epithelium. The epithelium contains goblet cells, which are glandular, modified simple columnar epithelial cells that produce mucins, the main component of mucus. Mucus helps to moisten and protect the airways.[5] Mucus lines the ciliated 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. This self-clearing mechanism is termed mucociliary clearance.[6]

Other Languages
Alemannisch: Luftröhre
العربية: قصبة هوائية
aragonés: Traquia
ܐܪܡܝܐ: ܚܪܘܫܬܐ
Aymar aru: Tunquri
azərbaycanca: Nəfəs borusu
Bân-lâm-gú: Khì-kńg
беларуская: Трахея
беларуская (тарашкевіца)‎: Трахея
български: Дихателна тръба
bosanski: Dušnik
català: Tràquea
čeština: Průdušnice
Cymraeg: Tracea
dansk: Luftrør
Deutsch: Luftröhre
ދިވެހިބަސް: ވައި ނޮޅި
eesti: Hingetoru
Ελληνικά: Τραχεία
español: Tráquea
Esperanto: Traĥeo
euskara: Trakea
فارسی: نای
français: Trachée
Frysk: Luchtpiip
Gaeilge: Píobán
Gaelg: Aahjioogh
한국어: 기관 (기도)
հայերեն: Շնչափող
हिन्दी: श्वासनली
hrvatski: Dušnik
Ido: Trakeo
Bahasa Indonesia: Trakea
italiano: Trachea
Basa Jawa: Trakéa
ქართული: ტრაქეა
қазақша: Кеңірдек
Kreyòl ayisyen: Trache
kurdî: Qilqancik
Latina: Trachea
latviešu: Traheja
lietuvių: Trachėja
Limburgs: Lóchpiep
magyar: Légcső
македонски: Дишник
Bahasa Melayu: Trakea vertebrat
Nederlands: Luchtpijp
日本語: 気管
norsk: Luftrør
norsk nynorsk: Luftrøyr
oʻzbekcha/ўзбекча: Traxeya
polski: Tchawica
português: Traqueia
română: Trahee
Runa Simi: Hatun tunqur
русский: Трахея
Scots: Trachea
Simple English: Trachea
slovenčina: Priedušnica
slovenščina: Sapnik
Soomaaliga: Hunguriga neefta
کوردی: تراشە
српски / srpski: Душник
srpskohrvatski / српскохрватски: Dušnik
suomi: Henkitorvi
svenska: Luftstrupe
татарча/tatarça: Трахея
Türkçe: Soluk borusu
українська: Трахея
ئۇيغۇرچە / Uyghurche: كاناي
Vahcuengh: Hozgyongx
Tiếng Việt: Khí quản
ייִדיש: לופטרער
粵語: 氣管
中文: 氣管