Editing Trachea

{{short description|Cartilaginous tube that connects the pharynx and larynx to the lungs}}
{{About||the genus of moth|Trachea (moth){{!}}''Trachea'' (moth)|the cup-shaped Byzantine coins|Trachy (currency)}}
{{Use dmy dates|date=April 2017}}
{{Infobox anatomy
| Name        = Trachea
| Latin       = trachea
| pronunciation = {{IPAc-en|t|r|ə|ˈ|k|iː|ə|,_|ˈ|t|r|eɪ|k|i|ə}}<ref>{{cite web |title=Trachea {{!}} Definition of Trachea by Lexico |url=https://www.lexico.com/en/definition/trachea |archive-url=https://web.archive.org/web/20200707001255/https://www.lexico.com/en/definition/trachea |url-status=dead |archive-date=7 July 2020 |website=Lexico Dictionaries {{!}} English |access-date=27 October 2019 |language=en}}</ref>
| Image      = Illu_conducting_passages.svg
| Caption     = Human trachea
| Width       = 
| Image2      =
| Caption2    =
| Precursor   = 
| System      = 
| Artery      = [[Tracheal branches of inferior thyroid artery]]
| Vein        = [[Brachiocephalic vein]], [[azygos vein]] [[accessory hemiazygos vein]]
| Nerve       = 
| PartOf      = [[Respiratory tract]]
| Lymph       = 
}}
The '''trachea''' ({{plural form}}: '''tracheae''' or '''tracheas'''), also known as the '''windpipe''', is a [[cartilaginous]] tube that connects the [[larynx]] to the [[bronchi]] of the [[lung]]s, allowing the passage of [[air]], and so is present in almost all [[animal]]s' 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. The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying [[annular ligaments of trachea|ligaments]], and by the [[trachealis muscle]] at their ends. The [[epiglottis]] closes the opening to the larynx during swallowing.

The trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time. Its [[epithelium]] is lined with [[columnar epithelium|column-shaped cells]] that have hair-like extensions called [[cilia]], with scattered [[goblet cell]]s that produce protective [[mucin]]s. The trachea can be affected by inflammation or infection, usually as a result of a viral illness affecting other parts of the [[respiratory tract]], such as the larynx and bronchi, called [[croup]], that can result in a cough. Infection with [[bacteria]] usually affects the trachea only and can cause narrowing or even obstruction. As a major part of the respiratory tract, the trachea, when obstructed, prevents air from entering the lungs; thus, a [[tracheostomy]] may be required. Additionally, during surgery, if [[mechanical ventilation]] is required during anaesthesia, [[tracheal tube|a&nbsp;tube]] is inserted into the trachea: this is called [[tracheal intubation]].

The word ''trachea'' is used to define a very different organ in [[invertebrate]]s than in [[vertebrate]]s. [[Insect]]s have an open [[respiratory system of insects|respiratory system]] made up of [[Spiracle (arthropods)|spiracles]], tracheae, and [[tracheole]]s to transport [[metabolic]] gases to and from tissues.

== Structure ==
[[File:Blausen 0865 TracheaAnatomy.png|thumb]]

An adult's trachea has an inner diameter of about {{convert|1.5|to|2|cm|frac=4}} and a length of about {{convert|10|to|11|cm|frac=4|abbr=on}}, wider in males than females.<ref name=GA2016>{{Cite book|title=Gray's anatomy : the anatomical basis of clinical practice| veditors = Standring S |isbn=9780702052309|edition=41st|location=Philadelphia|oclc=920806541|year=2016|pages=965–969|section=Trachea and bronchi| last1 = Standring | first1 = Susan }}</ref> The trachea begins at the lower edge of the [[cricoid cartilage]] of the larynx<ref name="Furlow2018">{{cite journal |vauthors=Furlow PW, Mathisen DJ |date=March 2018 |title=Surgical anatomy of the trachea |journal=Annals of Cardiothoracic Surgery |volume=7 |issue=2 |pages=255–260 |doi=10.21037/acs.2018.03.01 |pmc=5900092 |pmid=29707503 |doi-access=free}}</ref> at the level of sixth [[cervical vertebra]] (C6)<ref name=GA2016 /> and ends at the carina, the point where the trachea branches into left and right main bronchi.,<ref name="GA2016" /> at the level of the fourth [[thoracic vertebra]] (T4),<ref name=GA2016 /> although its position may change with [[breathing]].<ref name="Furlow2018" /> The trachea is surrounded by 16–20 rings of [[hyaline cartilage]]; these 'rings' are 4 millimetres high in the adult, incomplete and C-shaped.<ref name="GA2016" /> Ligaments connect the rings.<ref name="Furlow2018" /> The [[trachealis muscle]] connects the ends of the incomplete rings and runs along the back wall of the trachea.<ref name="Furlow2018" /> Also adventitia, which is the outermost layer of connective tissue that surrounds the hyaline cartilage, contributes to the trachea's ability to bend and stretch with movement.<ref>{{cite journal | vauthors = Ohkimoto K, Mouri M, Amatsu M, Teraoka M | title = [Histological study of the tracheal adventitia, perichondrium and annular ligament] | journal = Nihon Jibiinkoka Gakkai Kaiho | volume = 100 | issue = 11 | pages = 1394–1400 | date = November 1997 | pmid = 9423323 | doi = 10.3950/jibiinkoka.100.1394 | doi-access = free }}</ref>

Although trachea is a midline structure, it can be  displaced normally to the right by the aortic arch.<ref name="pmid8462036">{{cite journal | vauthors = Dennie CJ, Coblentz CL | title = The trachea: normal anatomic features, imaging and causes of displacement | journal = Canadian Association of Radiologists Journal | volume = 44 | issue = 2 | pages = 81–9 | date = April 1993 | pmid = 8462036 | doi = | url = }}</ref>

=== Nearby structures ===
The trachea passes by many structures of the [[neck]] and chest ([[thorax]]) along its course.

In front of the upper trachea lies connective tissue and skin.<ref name="GA2016" /> Several other structures pass over or sit on the trachea; the [[Jugular venous arch|jugular arch]], which joins the two [[anterior jugular vein]]s, sits in front of the upper part of the trachea. The [[Sternohyoid muscle|sternohyoid]] and [[sternothyroid muscle]]s stretch along its length. The thyroid gland also stretches across the upper trachea, with the isthmus overlying the second to fourth rings, and the lobes stretching to the level of the fifth or sixth cartilage.<ref name="GA2016" /> The blood vessels of the thyroid rest on the trachea next to the isthmus; [[superior thyroid arteries]] join just above it, and the [[inferior thyroid veins]] below it.<ref name="GA2016" /> In front of the lower trachea lies the manubrium of the [[sternum]], the [[Thymus#Involution|remnants]] of the [[thymus]] in adults. To the front left lie the large blood vessels the [[aortic arch]] and its branches the left [[common carotid artery]] and the [[Brachiocephalic artery|brachiocephalic trunk]]; and the left [[brachiocephalic vein]]. The deep [[cardiac plexus]] and lymph nodes are also positioned in front of the lower trachea.<ref name="GA2016" />

Behind the trachea, along its length, sits the [[Esophagus|oesophagus]], followed by connective tissue and the [[vertebral column]].<ref name=GA2016 /> To its sides run the [[carotid arteries]] and inferior thyroid arteries; and to its sides on its back surface run the [[recurrent laryngeal nerve]]s in the upper trachea, and the [[vagus nerve]]s in the lower trachea.<ref name=GA2016 />

The trachealis muscle contracts during [[cough]]ing, reducing the size of the [[lumen (anatomy)|lumen]] of the trachea.<ref name="Furlow2018" />

<gallery>
File:CT-Thorax-5.0-B70f.ogg|CT scan of the thorax (axial lung window)
File:COR-2-STND-CHEST.ogg|CT scan of the thorax (coronal lung window) 
File:COR-2-STND-CHEST-MEDIASTINUM.ogg|CT scan of the thorax (coronal mediastinal window) 
File:Cross section of a trachea and esophagus.svg|Cross section of a trachea and esophagus
File:Sternohyoid muscle.PNG|The [[sternohyoid muscle|sternohyoid]] and [[sternothyroid muscle]]s lie on top of the upper part of the trachea
File:Blausen 0534 Goiter.png|The thyroid gland also lies on top of the trachea, and lies below the cricoid cartilage. 
</gallery>

===Blood and lymphatic supply===
[[File:Gray622.png|thumb|[[Lymph node]]s of the trachea]]

The upper part of trachea receives and drains [[blood]] through the [[inferior thyroid arteries]] and veins;<ref name=GA2016 /> the lower trachea receives blood from bronchial arteries.<ref name="Furlow2018" /> Arteries that supply the trachea do so via small branches that supply the trachea from the sides. As the branches approach the wall of the trachea, they split into [[Anatomical terms of location#Superior and inferior|inferior and superior]] branches, which join with the branches of the arteries above and below; these then split into branches that supply the anterior and posterior parts of the trachea.<ref name="Furlow2018" /> The inferior thyroid arteries arise just below the isthmus of the thyroid, which sits atop the trachea. These arteries join ({{wt|en|anastamoses}}) with ascending branches of the [[bronchial artery|bronchial arteries]], which are direct branches from the [[aorta]], to supply blood to the trachea.<ref name=GA2016 /> The [[lymphatic vessel]]s of the trachea drain into the [[pretracheal lymph nodes|pretracheal nodes]] that lie in front of the trachea, and [[paratracheal lymph nodes]] that lie beside it.<ref name=GA2016 />

===Development===
In the fourth week of [[human embryogenesis|development of the human embryo]] as the [[respiratory bud]] grows, the trachea separates from the [[foregut]] through the formation of ridges which eventually separate the trachea from the oesophagus, the [[tracheoesophageal septum]]. This separates the future trachea from the oesophagus and divides the foregut tube into the laryngotracheal tube.<ref name=Langmans2019 >{{cite book | vauthors = Sadley TW |title=Langman's medical embryology |date=2019|location=Philadelphia|publisher=Wolters Kluwer |isbn=9781496383907 |edition=14th|pages=223–229}}</ref> By the start of the fifth week, the left and right main bronchi have begun to form, initially as buds at the terminal end of the trachea.<ref name=Langmans2019 />

The trachea is no more than 4&nbsp;mm in diameter during the first year of life, expanding to its adult diameter of approximately 2&nbsp;cm by late childhood.<ref name=GA2016 /><ref name="Furlow2018" /> The trachea is more circular and more vertical in children compared to adults,<ref name="Furlow2018" /> varies more in size, and also varies more in its position in relation to its surrounding structures.<ref name="GA2016" />

===Microanatomy===
The trachea is lined with a layer of [[pseudostratified ciliated columnar epithelium|interspersed layers of column-shaped cells with cilia]].<ref name="Furlow2018" /> The [[epithelium]] contains [[goblet cell]]s,  which are [[gland]]ular, column-shaped cells that produce [[mucins]], the main component of [[mucus]]. Mucus helps to moisten and protect the airways.<ref>{{cite book | vauthors = Mescher AL | chapter = Chapter 17. The Respiratory System | veditors = Mescher AL | title = Junqueira's Basic Histology: Text & Atlas | date = 28 August 2009 | publisher = McGraw Hill Professional | edition = 12th | url = http://www.accessmedicine.com/content.aspx?aID=6182422 |access-date=2015-02-24 |url-status=dead |archive-url=https://web.archive.org/web/20130603013209/http://www.accessmedicine.com/content.aspx?aid=6182422 |archive-date=3 June 2013 | isbn = 978-0-07-163020-7 }}</ref> 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]].<ref>{{cite journal | vauthors = Antunes MB, Cohen NA | title = Mucociliary clearance--a critical upper airway host defense mechanism and methods of assessment | journal = Current Opinion in Allergy and Clinical Immunology | volume = 7 | issue = 1 | pages = 5–10 | date = February 2007 | pmid = 17218804 | doi = 10.1097/aci.0b013e3280114eef | s2cid = 9551913 }}</ref> Directly beneath this mucus layer lies the submucosa layer which is composed primarily of fibrous connective tissue and connects the mucosa to the rings of hyaline cartilage beneath.<ref>Ayyalasomayajula, Venkat, and Bjørn Skallerud. “Microstructure and Mechanics of the Bovine Trachea: Layer Specific Investigations through SHG Imaging and Biaxial Testing.” Journal of the Mechanical Behavior of Biomedical Materials, vol. 134, 1 Oct. 2022, p. 5, https://doi.org/10.1016/j.jmbbm.2022.105371.</ref>

The trachea is surrounded by 16 to 20 rings of hyaline cartilage; these 'rings' are incomplete and C-shaped.<ref name=GA2016 /> 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 [[calcification|calcify]] with [[ageing|age]].
{{Clear left}}
<gallery>
File:Gray964.png|Cross-section
File:2308 The Trachea-b.jpg|Cross-section of the trachea, with pseudostratified ciliated columnar epithelium and goblet cells labelled
File:Cartilage01.JPG|Magnified cross-section of the cartilage of the trachea 
</gallery>

== Function ==
The trachea's main function is to transport air to and from the lungs. It also helps to warm, humidify, and filter the air before it reaches the lungs.

The trachea is made up of rings of cartilage, which help to keep it open and prevent it from collapsing. The inside of the trachea is lined with a mucous membrane, which produces mucus to help trap dirt and dust particles. The cilia, which are tiny hairs that line the mucous membrane, help to move the mucus and trapped particles up and out of the trachea.

==Clinical significance==
===Inflammation and infection===
<!--Intro and causes-->
[[Inflammation]] of the trachea is known as [[tracheitis]], usually due to an infection. It is usually caused by [[viral infection]]s,<ref name="Tristam2019">{{cite book | vauthors = Tristram D |title=Introduction to Clinical Infectious Diseases |chapter=Laryngitis, Tracheitis, Epiglottitis, and Bronchiolitis: Sore Throat, Change in Voice, Feverora Wheezing Infant in Respiratory Distress |date=2019 |publisher=Springer International Publishing |isbn=978-3-319-91080-2 |pages=75–85 |language=en |doi=10.1007/978-3-319-91080-2_7 |s2cid=86826724 }}</ref> with bacterial infections occurring almost entirely in children.<ref name=":1" /> Most commonly, infections occur with inflammation of other parts of the respiratory tract, such as the larynx and bronchi, known as [[croup]],<ref name=":1">{{cite journal | vauthors = Kuo CY, Parikh SR | title = Bacterial tracheitis | journal = Pediatrics in Review | volume = 35 | issue = 11 | pages = 497–499 | date = November 2014 | pmid = 25361911 | doi = 10.1542/pir.35-11-497 | s2cid = 42828725 }}</ref><ref name=Tristam2019/> however bacterial infections may also affect the trachea alone, although they are often associated with a recent viral infection.<ref name=Tristam2019/> Viruses that cause croup are generally the [[parainfluenza virus]]es 1–3, with [[influenza virus]]es A and B also causing croup, but usually causing more serious infections; bacteria may also cause croup and include ''[[Staphylococcus aureus]]'', ''[[Haemophilus influenzae]]'', ''[[Streptococcus pneumoniae]]'' and ''[[Moraxella catarrhalis]]''.<ref name=Tristam2019/> Causes of bacterial infection of the trachea are most commonly ''[[Staphylococcus aureus]]'' and ''[[Streptococcus pneumoniae]]''.<ref>{{cite web | vauthors = Bhatia R |title=Bacterial Tracheitis - Pediatrics |url=https://www.merckmanuals.com/professional/pediatrics/respiratory-disorders-in-young-children/bacterial-tracheitis |website=Merck Manuals Professional Edition |access-date=21 May 2020}}</ref> In patients who are in hospital, additional bacteria that may cause tracheitis include ''[[Escherichia coli]]'', ''[[Klebsiella pneumoniae]]'', and ''[[Pseudomonas aeruginosa]]''.<ref name=Tristam2019/>

<!--Symptoms and management-->
A person affected with tracheitis may start with symptoms that suggest an [[upper respiratory tract infection]] such as a cough, [[sore throat]], or [[Coryza|coryzal symptoms]] such as a [[runny nose]]. Fevers may develop and an affected child may develop [[respiratory distress|difficulty breathing]] and [[sepsis]].<ref name=Tristam2019/><ref name=":1" /> Swelling of the airway can cause narrowing of the airway, causing a hoarse breathing sound called [[stridor]], or even cause complete blockage.<ref name=":1" /> Up to 80% of people affected by bacterial tracheitis require [[intubation|the use of mechanical ventilation]], and treatment may include [[endoscopy]] for the purposes of acquiring microbiological specimens for [[culture and sensitivity]], as well as removal of any dead tissue associated with the infection. Treatment in such situations usually includes [[antibiotic]]s.<ref name=":1" />

===Narrowing===
[[File:Stridor NP OGG 2.ogg|thumb|An example of [[stridor]], which develops when the trachea is narrowed or obstructed]]

A trachea may be [[tracheal stenosis|narrowed or compressed]], usually a result of enlarged nearby lymph nodes; cancers of the trachea or nearby structures; large thyroid [[goitre]]s; or rarely as a result of other processes such as [[aneurysm|unusually swollen blood vessel]]s.<ref name=Davidsons2018 /> Scarring from [[tracheobronchial injury]] or intubation; or inflammation associated with [[granulomatosis with polyangiitis]] may also cause a narrowing of the trachea ([[tracheal stenosis]]).<ref name=Davidsons2018 /> Obstruction invariably causes a harsh breathing sound known as [[stridor]].<ref name=Davidsons2018 /> A camera inserted via the mouth down into the trachea, called [[bronchoscopy]], may be performed to investigate the cause of an obstruction.<ref name=Davidsons2018 /> Management of obstructions depends on the cause. Obstructions as a result of malignancy may be managed with surgery, [[chemotherapy]] or [[radiotherapy]].<ref name=Davidsons2018 />  A stent may be inserted over the obstruction. Benign lesions, such as narrowing resulting from scarring, are likely to be surgically excised.<ref name=Davidsons2018 />

One cause of narrowing is [[tracheomalacia]], which is the tendency for the trachea to collapse when there is increased external pressure, such as when airflow is increased during breathing in or out, due to decreased [[Compliance (physiology)|compliance]].<ref name="Hysinger2016">{{cite journal | vauthors = Hysinger EB, Panitch HB | title = Paediatric Tracheomalacia | journal = Paediatric Respiratory Reviews | volume = 17 | pages = 9–15 | date = January 2016 | pmid = 25962857 | doi = 10.1016/j.prrv.2015.03.002 }}</ref> It can be due to congenital causes, or due to things that develop after birth, such as compression from nearby masses or swelling, or trauma.<ref name="Hysinger2016" /> Congenital tracheomalacia can occur by itself or in association with other abnormalities such as [[bronchomalacia]] or [[laryngomalacia]], and [[tracheoesophageal fistula|abnormal connections between the trachea and the oesophagus]], amongst others.<ref name="Hysinger2016" /> Congenital tracheomalacia often improves without specific intervention; when required, interventions may include [[beta agonist]]s and [[muscarinic agonists]], which enhance the tone of the smooth muscle surrounding the trachea; [[positive pressure ventilation]], or surgery, which may include the placement of a [[stent]], or the removal of the affected part of the trachea.<ref name="Hysinger2016" /> In dogs, particularly miniature dogs and [[toy dogs]], tracheomalacia, as well as [[bronchomalacia]],<ref>{{cite journal | vauthors = Johnson LR, Pollard RE | title = Tracheal collapse and bronchomalacia in dogs: 58 cases (7 /2001-1 /2008) | journal = Journal of Veterinary Internal Medicine | volume = 24 | issue = 2 | pages = 298–305 | date = March 2010 | pmid = 20051001 | doi = 10.1111/j.1939-1676.2009.0451.x | doi-access = free }}</ref> can lead to [[tracheal collapse]], which often presents with a honking goose-like cough.<ref>{{cite journal | vauthors = Maggiore AD | title = Tracheal and airway collapse in dogs | journal = The Veterinary Clinics of North America. Small Animal Practice | volume = 44 | issue = 1 | pages = 117–127 | date = January 2014 | pmid = 24268337 | doi = 10.1016/j.cvsm.2013.09.004 }}</ref>

===Injury===
The trachea may be injured by trauma such as in a vehicle accident, or intentionally by another wilfully inflicting damage for example as practiced in some [[martial arts]].<ref name="Santiago-Rosado">{{cite journal |last1=Santiago-Rosado |first1=Livia M. |last2=Sigmon |first2=David F. |last3=Lewison |first3=Cheryl S. |title=Tracheal Trauma |url=https://www.ncbi.nlm.nih.gov/books/NBK500015/ |website=StatPearls |publisher=StatPearls Publishing |access-date=23 October 2022 |date=2022|pmid=29763191 }}</ref>

===Intubation===
{{Main|Tracheal intubation |Airway management}}

Tracheal intubation refers to the insertion of a [[tracheal tube|tube]] down the trachea.<ref>{{cite web |title=Definition of INTUBATION |url=https://www.merriam-webster.com/dictionary/intubation |website=www.merriam-webster.com |publisher=Merriam Webster |access-date=25 May 2020 |language=en}}</ref> This procedure is commonly performed during [[surgery]], in order to ensure a person receives enough oxygen when sedated. The catheter is connected to a machine that monitors the airflow, oxygenation and several other metrics. This is often one of the responsibilities of an [[anaesthetist]] during surgery.

In an emergency, or when tracheal intubation is deemed impossible, a [[tracheotomy]] is often performed to insert a tube for ventilation, usually when needed for particular types of surgery to be carried out so that the airway can be kept open. The provision of the opening via a tracheotomy is called a [[tracheostomy]].<ref>{{cite web| vauthors = Molnar H |title=Types of Tracheostomy Tubes |date=11 April 2023 |url= http://www.hopkinsmedicine.org/tracheostomy/about/types.html|language=en}}</ref> Another method procedure can be carried, in an emergency situation, and this is a [[cricothyrotomy]].<ref>{{cite web |title=Medical Definition of CRICOTHYROTOMY |url=https://www.merriam-webster.com/medical/cricothyrotomy |website=www.merriam-webster.com |publisher=Merriam Webster |access-date=25 May 2020 |language=en}}</ref>

===Congenital disorders===
[[File:Tracheal diverticulum.png|thumb|Tracheal diverticulum as seen on axial CT imaging]]

[[Tracheal agenesis]]<ref>{{cite journal | vauthors = Chiu T, Cuevas D, Cuevas L, Monteiro C | title = Tracheal agenesis | journal = Southern Medical Journal | volume = 83 | issue = 8 | pages = 925–930 | date = August 1990 | pmid = 2200137 | doi = 10.1097/00007611-199008000-00018 | s2cid = 21260092 }}</ref> is a rare [[birth defect]] in which the trachea fails to develop. The defect is usually fatal though sometimes surgical intervention has been successful.

A [[tracheoesophageal fistula]] is a congenital defect in which the trachea and esophagus are abnormally connected (a {{wt|en|fistula}}). This is because of abnormalities in the separation between the trachea and oesophagus during development.<ref name=Langmans2019 /> This occurs in approximately 1 in 3,000 births, and the most common abnormalities is a separation of the upper and lower ends of the oesophagus, with the upper end finishing in a closed pouch.<ref name=Langmans2019 /> Other abnormalities may be associated with this, including cardiac abnormalities, or [[VACTERL syndrome]].<ref name=Langmans2019 /> Such fistulas may be detected before a baby is born because of [[polyhydramnios|excess amniotic fluid]]; after birth, they are often associated with pneumonitis and pneumonia because of {{wt|en|aspiration}} of food contents.<ref name=Langmans2019 /> Congenital fistulas are often treated by surgical repair.<ref name=Davidsons2018>{{cite book|title=Davidson's principles and practice of medicine| veditors = Ralston SH, Penman ID, Strachan MW, Hobson RP |date=2018 |publisher=Elsevier |isbn=978-0-7020-7028-0 |edition=23rd}}</ref> In adults, fistulas may occur because of erosion into the trachea from nearby malignant tumours, which erode into both the trachea and the oesophagus. Initially, these often result in coughing from swallowed contents of the oesophagus that are aspirated through the trachea, often progressing to fatal pneumonia; there is rarely a curative treatment.<ref name=Davidsons2018 /> A [[tracheo-oesophageal puncture]] is a surgically created hole between the trachea and the esophagus in a person who has had their larynx removed. Air travels upwards from the surgical connection to the upper oesophagus and the pharynx, creating vibrations that create sound that can be used for speech. The purpose of the puncture is to restore a person's ability to speak after the vocal cords have been removed.<ref>{{cite web |title=Evaluation and Treatment for Tracheoesophageal Puncture and Prosthesis: Technical Report |url=https://www.asha.org/policy/TR2004-00138/ |website=American Speech-Language-Hearing Association |publisher=American Speech-Language-Hearing Association (ASHA) |access-date=26 May 2020 |language=en |date=2004}}</ref>

Sometimes as an [[anatomical variation]] one or more of the tracheal rings are formed as complete rings, rather than horseshoe shaped rings. These ''O'' rings are smaller than the normal C-shaped rings and can cause narrowing ({{wt|en|stenosis}}) of the trachea, resulting in breathing difficulties. An operation called a ''slide tracheoplasty'' can open up the rings and rejoin them as wider rings, shortening the length of the trachea.<ref>{{cite web|title=Slide tracheoplasty|url=http://www.cincinnatichildrens.org/health/s/slide-tracheoplasty/|access-date=2 October 2015}}</ref> Slide tracheoplasty is said to be the best option in treating tracheal stenosis.<ref>{{cite journal | vauthors = Xue B, Liang B, Wang S, Zhu L, Lu Z, Xu Z | title = One-stage surgical correction of congenital tracheal stenosis complicated with congenital heart disease in infants and young children | journal = Journal of Cardiac Surgery | volume = 30 | issue = 1 | pages = 97–103 | date = January 2015 | pmid = 25109422 | doi = 10.1111/jocs.12418 | s2cid = 25335958 | doi-access = free }}</ref>

[[Mounier-Kuhn syndrome]] is a rare congenital disorder of an abnormally enlarged trachea, characterised by absent elastic fibres, smooth muscle thinning, and a tendency to get recurrent respiratory tract infections.<ref>{{cite journal | vauthors = Menon B, Aggarwal B, Iqbal A | title = Mounier-Kuhn syndrome: report of 8 cases of tracheobronchomegaly with associated complications | journal = Southern Medical Journal | volume = 101 | issue = 1 | pages = 83–87 | date = January 2008 | pmid = 18176298 | doi = 10.1097/SMJ.0b013e31815d4259 }}</ref>

===Replacement===
From 2008, operations have experimentally replaced tracheas, with those grown from [[stem cell]]s, or with synthetic substitutes, however this is regarded as experimental and there is no standardised method.<ref name="Tracheal replacement">{{cite journal | vauthors = Delaere P, Van Raemdonck D | title = Tracheal replacement | journal = Journal of Thoracic Disease | volume = 8 | issue = Suppl 2 | pages = S186–S196 | date = March 2016 | pmid = 26981270 | pmc = 4775267 | doi = 10.3978/j.issn.2072-1439.2016.01.85 }}</ref> Difficulties with ensuring adequate blood supply to the replaced trachea is considered a major challenge to any replacement. Additionally, no evidence has been found to support the placement of stem cells taken from [[bone marrow]] on the trachea as a way of stimulating tissue regeneration, and such a method remains hypothetical.<ref name="Tracheal replacement" />

In January 2021, surgeons at [[Mount Sinai Hospital (Manhattan)|Mount Sinai Hospital]] in New York performed the first complete trachea transplantation. The 18-hour procedure included harvesting a trachea from a donor and implanting it in the patient, connecting numerous veins and arteries to provide sufficient blood flow to the organ.<ref>{{cite news|url=https://www.npr.org/sections/health-shots/2021/04/06/981735718/woman-gets-new-windpipe-in-groundbreaking-transplant-surgery| title=Woman Gets New Windpipe In Groundbreaking Transplant Surgery| date=6 April 2021| access-date=6 April 2021| vauthors = Harris R | work=NPR}}</ref>

==Other animals==
Allowing for variations in the length of the neck, the trachea in other [[mammal]]s is, in general, similar to that in humans. Generally, it is also similar to the [[reptile|reptilian]] trachea.<ref name=VB>{{cite book | vauthors = Romer AS, Parsons TS |year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|pages= 336–337|isbn= 978-0-03-910284-5}}</ref>

===Vertebrates===
In [[bird]]s, the trachea runs from the [[pharynx]] to the [[syrinx (biology)|syrinx]], from which the primary bronchi diverge. [[Swan]]s 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 tracheal rings are complete, and may even be [[ossification|ossified]].<ref name=VB/>

In [[amphibian]]s, 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 [[salamander]]s, and in [[caecilian]]s. While there are irregular cartilagenous nodules on the amphibian trachea, these do not form the rings found in [[amniote]]s.<ref name=VB/>

The only [[vertebrate]]s to have lungs, but no trachea, are the [[lungfish]] and the ''[[Polypterus]]'', in which the lungs arise directly from the pharynx.<ref name=VB/>

===Invertebrates===
[[File:Tracheal system of dissected cockroach.tif|thumb|left|Tracheal system of dissected [[cockroach]].  The largest tracheae run across the width of the body of the cockroach and are horizontal in this image. Scale bar, 2 mm.]]
[[File:Cockroach tracheae supplying crop.tiff|thumb|The tracheal system branches into progressively smaller tubes, here supplying the [[Crop (anatomy)|crop]] of the cockroach.  Scale bar, 2 mm.]]

The word ''trachea'' is used to define a very different organ in [[invertebrate]]s than in vertebrates. Insects have an open [[respiratory system of insects|respiratory system]] made up of spiracles, tracheae, and [[tracheole]]s to transport [[metabolism|metabolic]] gases to and from tissues.<ref>Wasserthal, Lutz T. (1998). Chapter 25: The Open Hemolymph System of Holometabola and Its Relation to the Tracheal Space. In "Microscopic Anatomy of Invertebrates". Wiley-Liss, Inc. {{ISBN|0-471-15955-7}}.</ref> The distribution of spiracles can vary greatly among the many [[order (biology)|orders]] of [[insect]]s, but in general each segment of the body can have only one pair of spiracles, each of which connects to an atrium and has a relatively large tracheal tube behind it. The tracheae are invaginations of the cuticular [[exoskeleton]] that branch ([[anastomosis|anastomose]]) throughout the body with diameters from only a few micrometres up to 0.8&nbsp;mm. [[Diffusion]] of oxygen and [[carbon dioxide]] takes place across the walls of the smallest tubes, called tracheoles, which penetrate tissues and even indent individual cells.<ref name=":0">{{Cite book|title=Borror and DeLong's introduction to the study of insects| vauthors = Triplehorn C, Johnson NF, Borror DJ |publisher=Thompson Brooks/Cole |year=2005|isbn=978-0030968358|edition= 7th |location=Belmont, CA|pages=28–29|oclc=55793895}}</ref> Gas may be conducted through the respiratory system by means of active [[Ventilation (physiology)|ventilation]] or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their [[hemolymph]].<ref>{{cite journal | vauthors = Westneat MW, Betz O, Blob RW, Fezzaa K, Cooper WJ, Lee WK | title = Tracheal respiration in insects visualized with synchrotron x-ray imaging | journal = Science | volume = 299 | issue = 5606 | pages = 558–560 | date = January 2003 | pmid = 12543973 | doi = 10.1126/science.1078008 | s2cid = 43634044 | bibcode = 2003Sci...299..558W }}</ref>
This is one of the factors that may limit their size.

A tracheal tube may contain ridge-like circumferential rings of [[taenidia]] in various [[geometry|geometries]] such as loops or [[helix|helices]]. Taenidia provide strength and flexibility to the trachea. In the head, thorax, or [[abdomen]], tracheae may also be connected to air sacs. Many insects, such as [[grasshopper]]s and [[bee]]s, which actively pump the air sacs in their abdomen, are able to control the flow of air through their body. In some aquatic insects, the tracheae exchange gas through the body wall directly, in the form of a [[gill]], or function essentially as normal, via a [[Gill#Plastron|plastron]]. Note that despite being internal, the tracheae of arthropods are lined with cuticular tissue and are shed during moulting ([[ecdysis]]).<ref name=":0" />

==Additional images==
<gallery>
File:Trachea (mammal) histology cross-section.png|alt=Trachea (mammal) cross-section high resolution|Trachea (mammal) cross-section high resolution
File:Trachea (mammal) histology cross-section low mag.png|alt=Trachea (mammal) cross-section low resolution|Trachea (mammal) cross-section low resolution
File:Larynx detailed.jpg|Trachea
File:Gray954.png|Coronal section of larynx and upper part of trachea
</gallery>
[[File:3d-vh-m-trachea.stl|thumb|The graph representation of the 3D Reference Organ for Trachea, Male dataset.]]

== References ==
{{Reflist|30em}}

{{Human systems and organs}}
{{Lower respiratory system anatomy}}

{{Authority control}}

{{good article}}

[[Category:Trachea| ]]
[[Category:Arthropod anatomy]]
[[Category:Invertebrate respiratory system]]
[[Category:Human head and neck]]
[[Category:Thorax (human anatomy)]]
[[Category:Respiratory system anatomy]]