View source for Esophagus

{{short description|Vertebrate organ through which food passes to the stomach}}
{{Redirect|Gullet}}
{{Use American English|date=March 2021}}
{{Use dmy dates|date=March 2021}}
{{good article}}
{{Infobox anatomy
| Name      = Esophagus 
| Latin     = oesophagus
| Greek     = οἰσοφάγος
| Image     = Tractus intestinalis esophagus.svg
| Caption   = The [[digestive tract]], with the esophagus marked in red
| Width     =  150
| Image2    =
| Caption2  =
| Precursor = [[Foregut]]
| System    = [[Digestion|Digestive system]]
| Artery    = [[Esophageal arteries]]
| Vein      = [[Esophageal veins]]
| Nerve     = [[Sympathetic trunk]], [[vagus]]
| Lymph     =
}}
{{Gastrointestinal tract sidebar}}
{{Digestive system diagram}}

The '''esophagus''' ([[American English]]), '''oesophagus''' ([[British English]]), or œsophagus ([[Œ|archaic spelling]]) ([[American and British English spelling differences#ae and oe|see spelling difference]]) all {{IPAc-en|iː|ˈ|s|ɒ||f|ə|ɡ|ə|s|,_|ɪ|-|audio=LL-Q1860 (eng)-Flame, not lame-Esophagus.wav}};<ref>{{cite LPD|3}}</ref> {{plural form}}: '''((o)e)(œ)sophagi''' or ('''(o)e)(œ)sophaguses'''), colloquially known also as the '''food pipe''', '''food tube''', or '''gullet''', is an [[Organ (anatomy)|organ]] in [[vertebrate]]s through which [[food]] passes, aided by [[Peristalsis|peristaltic contractions]], from the [[Human pharynx|pharynx]] to the [[stomach]]. The esophagus is a [[:wiktionary:fibromuscular|fibromuscular]] tube, about {{convert|25|cm|in|abbr=on|sigfig=1}} long in adult humans, that travels behind the [[trachea]] and [[human heart|heart]], passes through the [[Thoracic diaphragm|diaphragm]], and empties into the uppermost region of the [[stomach]]. During swallowing, the [[epiglottis]] tilts backwards to prevent food from going down the [[larynx]] and lungs. The word ''esophagus'' is from Ancient Greek οἰσοφάγος (oisophágos), from οἴσω (oísō), future form of φέρω (phérō, "I carry") + ἔφαγον (éphagon, "I ate").

The wall of the esophagus from the [[Lumen (anatomy)|lumen]] outwards consists of [[mucosa]], [[submucosa]] (connective tissue), [[muscular layer|layers of muscle fibers]] between layers of [[fibrous tissue]], and an outer layer of connective tissue. The mucosa is a [[stratified squamous epithelium]] of around three layers of squamous cells, which contrasts to the [[simple columnar epithelia|single layer of columnar cells]] of the stomach. The transition between these two types of epithelium is visible as a zig-zag line. Most of the muscle is [[smooth muscle]] although [[striated muscle]] predominates in its upper third. It has two muscular rings or [[sphincter]]s in its wall, one at the top and one at the bottom. The lower sphincter helps to prevent reflux of acidic stomach content. The esophagus has a rich blood supply and venous drainage. Its smooth muscle is innervated by involuntary nerves ([[sympathetic nerve]]s via the [[sympathetic trunk]] and [[parasympathetic nerve]]s via the [[vagus nerve]]) and in addition voluntary nerves ([[lower motor neurons]]) which are carried in the vagus nerve to innervate its striated muscle.

The esophagus may be affected by [[GERD|gastric reflux]], [[esophageal cancer|cancer]], prominent dilated blood vessels called [[esophageal varices|varices]] that can bleed heavily, [[Mallory-Weiss Syndrome|tears]], constrictions, and disorders of motility. Diseases may cause difficulty swallowing ([[dysphagia]]), painful swallowing ([[odynophagia]]), [[chest pain]], or cause no symptoms at all. Clinical investigations include [[upper gastrointestinal series|X-rays]] when swallowing [[barium sulphate|barium sulfate]], [[endoscopy]], and [[CT scan]]s. Surgically, 
the esophagus is difficult to access in part due to its position between critical organs and directly between the sternum and spinal column.<ref>{{cite web|url=https://abcnews.go.com/Health/thanksgiving-tales-emergency-room/story?id=43746804|title=Thanksgiving Tales From the Emergency Room|first=Julia|last=Jacobo|date=24 November 2016|website=ABC News}}</ref>
{{TOC limit|3}}

==Structure==
The esophagus is one of the upper parts of the [[Digestion|digestive system]]. There are [[taste bud]]s on its upper part.<ref>{{cite book|last1=Purves|first1=Dale|title=Neuroscience|date=2011|publisher=Sinauer|location=Sunderland, MA|isbn=978-0-87893-695-3|page=341|edition=5th}}</ref> It begins at the back of the mouth, passing downward through the rear part of the [[mediastinum]], through the [[Thoracic diaphragm|diaphragm]], and into the stomach. In humans, the esophagus generally starts around the level of the sixth [[Cervical vertebrae|cervical vertebra]] behind the [[cricoid cartilage]] of the [[trachea]], enters the diaphragm at about the level of the [[tenth thoracic vertebra]], and ends at the [[cardia]] of the stomach, at the level of the [[eleventh thoracic vertebra]].<ref name=GRAYS2005>{{cite book|last1=Drake|first1=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|last2=Vogl|first2=Wayne|last3=Tibbitts|first3=Adam W.M. Mitchell|others=illustrations by Richard M. Tibbitts and Paul Richardson|pages=192–94}}</ref> The esophagus is usually about 25&nbsp;cm (10&nbsp;in) in length,<ref name=DAVIDSONS2010>{{cite book|editor-first=Nicki R.|editor-last=Colledge|editor-first2=Brian R.|editor-last2=Walker|editor-first3=Stuart H.|editor-last3=Ralston|others=illust. Robert Britton|title=Davidson's Principles and Practice of Medicine|url=https://archive.org/details/davidsonsprincip00frcp|url-access=limited|year=2010|publisher=Churchill Livingstone/Elsevier|location=Edinburgh|isbn=978-0-7020-3084-0|edition=21st|pages=[https://archive.org/details/davidsonsprincip00frcp/page/n854 838]–70}}</ref> with only around one centimeter of esophagus lying  in the abdominal cavity.<ref name="Chaurasia-2013b">{{Cite book|last=Chaurasia|first=B.D.|title=Human Anatomy|publisher=CBS Publishers and Distributors|year=2013|isbn=978-81-239-2331-4|edition=6th|volume=2|location=4819/XI, Prahlad Street, 24 Ansari Road, Daryganj, New Delhi 110002, India|page=248|chapter=19}}</ref>

Many [[blood vessel]]s serve the esophagus, with blood supply varying along its course. The upper parts of the esophagus and the upper esophageal sphincter receive blood from the [[inferior thyroid artery]], the parts of the esophagus in the thorax from the [[bronchial artery|bronchial arteries]] and branches directly from the [[thoracic aorta]], and the lower parts of the esophagus and the lower esophageal sphincter receive blood from the [[left gastric artery]] and the left [[inferior phrenic artery]].<ref name=KUO2006/><ref name=PATTI1997>{{cite journal|last=Patti|first=MG|author2=Gantert, W|author3=Way, LW|title=Surgery of the esophagus. Anatomy and physiology.|journal=The Surgical Clinics of North America|date=Oct 1997|volume=77|issue=5|pages=959–70|pmid=9347826|doi=10.1016/s0039-6109(05)70600-9}}</ref> The venous drainage also differs along the course of the esophagus. The upper and middle parts of the esophagus drain into the [[azygos vein|azygos]] and [[hemiazygos vein]]s, and blood from the lower part drains into the [[left gastric vein]]. All these veins drain into the [[superior vena cava]], with the exception of the left gastric vein, which is a branch of the [[portal vein]].<ref name=KUO2006/> Lymphatically, the upper third of the esophagus drains into the [[deep cervical lymph node]]s, the middle into the superior and posterior mediastinal lymph nodes, and the lower esophagus into the [[gastric lymph nodes|gastric]] and [[celiac lymph nodes]]. This is similar to the lymphatic drainage of the abdominal structures that arise from the [[foregut]], which all drain into the celiac nodes.<ref name=KUO2006/> 
;Position
{{multiple image
| align    = right

| image1   = Relations of the aorta, trachea, esophagus and other heart structures.png
| width1   = 200
| alt1     = Diagram showing the esophagus passing behind the human trachea and heart.
| caption1 = The esophagus (yellow) passes behind the [[human trachea|trachea]] and the [[human heart|heart]].

| image2   = Gray1032.png 
| width2   = 200
| alt2     = Diagram of thorax showing the esophagus and surrounding structures.
| caption2 = The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind.
}}
The upper esophagus lies at the back of the mediastinum behind the [[trachea]], adjoining along the [[tracheoesophageal stripe]], and in front of the [[erector spinae muscle]]s and the [[vertebral column]]. The lower esophagus lies behind the [[heart]] and curves in front of the [[thoracic aorta]]. From the [[Carina of trachea|bifurcation of the trachea]] downwards, the esophagus passes behind the right [[pulmonary artery]], [[left main bronchus]], and [[left atrium]]. At this point, it passes through the diaphragm.<ref name=GRAYS2005 />

The [[thoracic duct]], which drains the majority of the body's [[lymph]], passes behind the esophagus, curving from lying behind the esophagus on the right in the lower part of the esophagus, to lying behind the esophagus on the left in the upper esophagus. The esophagus also lies in front of parts of the [[hemiazygos vein]]s and the [[intercostal vein]]s on the right side. The [[vagus nerve]] divides and covers the esophagus in a [[plexus]].<ref name=GRAYS2005 />

;Constrictions
[[File:Illu esophagus.jpg|thumbnail|The esophagus is constricted in three places.{{Inconsistent|date= June 2020|reason= Constrictions subsection states 'four points'. Also, image does not show points of constriction}}|alt=Diagram showing the four constrictions of the esophagus.]]
The esophagus has four points of constriction. When a corrosive substance, or a solid object is swallowed, it is most likely to lodge and damage one of these four points. These constrictions arise from particular structures that compress the esophagus. These constrictions are:<ref name=GRAYS2009>{{cite book|last1=Drake|first1=Richard L.|title=Gray's anatomy for students|year=2009|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-443-06952-9|last2=Vogl|first2=Wayne|last3=Mitchell|first3=Adam W.M.|others=illustrations by Richard M. Tibbitts and Paul Richardson|page=215}}</ref>
* At the start of the esophagus, where the [[Pharynx#Laryngopharynx|laryngopharynx]] joins the esophagus, behind the [[cricoid cartilage]]
* Where it is crossed on the front by the [[aortic arch]] in the superior [[mediastinum]]
* Where the esophagus is compressed by the left main [[bronchus]] in the posterior mediastinum
* The [[esophageal hiatus]], where it passes through the [[Thoracic diaphragm|diaphragm]] in the posterior mediastinum

===Sphincters===<!-- Other articles link here -->
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[[esophageal sphincter]], 
[[esophageal sphincter, upper]], 
[[esophageal sphincter, lower]], 
[[upper esophageal sphincter]], 
[[lower esophageal sphincter]], and 
[[cardiac sphincter]]. 
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The esophagus is surrounded at the top and bottom by two muscular rings, known respectively as the upper esophageal sphincter and the lower esophageal sphincter.<ref name=GRAYS2005 /> These [[sphincter]]s act to close the esophagus when food is not being swallowed. The upper esophageal sphincter is an anatomical sphincter, which is formed by the lower portion of the inferior pharyngeal constrictor, also known as the cricopharyngeal sphincter due to its relation with [[cricoid cartilage]] of the [[larynx]] anteriorly. However, the lower esophageal sphincter is not an anatomical but rather a functional sphincter, meaning that it acts as a sphincter but does not have a distinct thickening like other sphincters.{{citation needed|date=October 2025}}

The upper esophageal sphincter surrounds the upper part of the esophagus. It consists of [[skeletal muscle]] but is not under [[muscle contraction|voluntary control]]. Opening of the upper esophageal sphincter is triggered by the [[Pharyngeal reflex|swallowing reflex]]. The primary muscle of the upper esophageal sphincter is the [[inferior pharyngeal constrictor muscle#Origin and insertion|cricopharyngeal part]] of the [[inferior pharyngeal constrictor]].<ref>{{Cite journal|last1=Mu|first1=L|last2=Wang|first2=J|last3=Su|first3=H|last4=Sanders|first4=I|title=Adult human upper esophageal sphincter contains specialized muscle fibers expressing unusual myosin heavy chain isoforms|journal=J. Histochem. Cytochem.|volume=55|issue=3|pages=199–207|date=March 2007|pmid=17074861|doi=10.1369/jhc.6A7084.2006|doi-access=free}}</ref>

The lower esophageal sphincter, or gastroesophageal sphincter, surrounds the lower part of the esophagus at the [[gastroesophageal junction]] between the esophagus and the stomach.<ref name=GUYTONHALL2005 /> It is also called the cardiac sphincter or cardioesophageal sphincter, named from the adjacent part of the stomach, the ''[[cardia]]''. Dysfunction of the gastroesophageal sphincter causes gastroesophageal [[wikt:reflux#Noun|reflux]], which causes [[heartburn]], and, if it happens often enough, can lead to [[gastroesophageal reflux disease]], with damage of the esophageal mucosa.<ref name="Kahrilas">{{cite journal|author=Kahrilas PJ|title=Gastroesophageal Reflux Disease|journal=[[The New England Journal of Medicine]]|volume=359|issue=16|pages=1700–07|year=2008|pmid=18923172|pmc=3058591|doi=10.1056/NEJMcp0804684}}</ref>

===Nerve supply===
The esophagus is innervated by the [[vagus nerve]] and the cervical and thoracic [[sympathetic trunk]].<ref name="KUO2006" /> The vagus nerve has a [[parasympathetic nerve|parasympathetic]] function, supplying the muscles of the esophagus and stimulating glandular contraction. Two sets of nerve fibers travel in the vagus nerve to supply the muscles. The upper striated muscle, and upper esophageal sphincter, are supplied by neurons with bodies in the [[nucleus ambiguus]], whereas fibers that supply the smooth muscle and lower esophageal sphincter have bodies situated in the [[dorsal motor nucleus]].<ref name="KUO2006" /> The vagus nerve plays the primary role in initiating [[peristalsis]].<ref>{{cite journal|last=Patterson|first=William G.|title=Esophageal peristalsis|journal=GI Motility Online|date=2006|doi=10.1038/gimo13|url=http://www.nature.com/gimo/contents/pt1/full/gimo13.html|access-date=24 May 2014|doi-broken-date=12 July 2025}}</ref> The sympathetic trunk has a [[sympathetic nerve|sympathetic]] function. It may enhance the function of the vagus nerve, increasing peristalsis and glandular activity, and causing sphincter contraction. In addition, sympathetic activation may relax the muscle wall and cause blood vessel constriction.<ref name="KUO2006" /> Sensation along the esophagus is supplied by both nerves, with gross sensation being passed in the vagus nerve and pain passed up the sympathetic trunk.<ref name="GRAYS2005" />

===Gastroesophageal junction===
The gastroesophageal junction (also known as the esophagogastric junction) is the junction between the esophagus and the stomach, at the lower end of the esophagus.<ref>{{Cite encyclopedia|title=Stedman's Concise Medical and Allied Health Dictionary|editor= John H. Dirckx|year=1997|isbn=978-0-683-23125-0|publisher=[[Williams and Wilkins]]|edition=3rd|page=463}}</ref> The pink color of the esophageal mucosa contrasts to the deeper red of the [[gastric mucosa]],<ref name=KUO2006/><ref name=GD2002>{{cite book|editor1= Anthony DiMarino, Jr.|editor2=Stanley B. Benjamin|others=section editors Firas H. Al-Kawas|title=Gastrointestinal disease: an endoscopic approach|year=2002|publisher=Slack|location=Thorofare, NJ|isbn=978-1-55642-511-0|page=166|edition=2nd}}</ref> and the mucosal transition can be seen as an irregular zig-zag line, which is often called the z-line.<ref>{{cite book|editor1=Richard M. Gore|editor2=Marc S. Levine|title=High-yield imaging|date=2010|publisher=Saunders/Elsevier|location=Philadelphia|isbn=978-1-4557-1144-4|page=151|edition=1st}}</ref> Histological examination reveals abrupt transition between the [[stratified squamous epithelium]] of the esophagus and the [[simple columnar epithelium]] of the [[stomach]].<ref name="Moore-Agur">{{cite book|title=Essential Clinical Anatomy|url=https://archive.org/details/essentialclinica02edmoor|url-access=registration|edition=2nd|first1=Keith L|last1=Moore|first2=Anne M.R|last2=Agur|publisher=[[Lippincott Williams & Wilkins]]|year=2002|isbn=978-0-7817-2830-0|page=[https://archive.org/details/essentialclinica02edmoor/page/145 145]}}</ref> Normally, the [[stomach#Sections|cardia]] of the stomach is immediately distal to the z-line<ref>{{cite book|last=Barrett|first=Kim E.|title=Gastrointestinal physiology|year=2014|publisher=Mc Graw Hill.|location=New York|isbn=978-0-07-177401-7|pages=Chapter 7: "Esophageal Motility"|edition=2nd}}</ref> and the z-line coincides with the upper limit of the gastric folds of the cardia; however, when the anatomy of the mucosa is distorted in [[Barrett's esophagus]] the true gastroesophageal junction can be identified by the upper limit of the gastric folds rather than the mucosal transition.<ref>{{cite book|title=Specialist Training in Gastroenterology and Liver Disease|editor1-first=Richard G|editor1-last=Long|editor2-first=Brian B|editor2-last=Scott|isbn=978-0-7234-3252-4|publisher=Elsevier Mosby|year=2005|pages=25–26}}</ref> The functional location of the lower oesophageal sphincter is generally situated about {{convert|3|cm|in|abbr=on|frac=4}} below the z-line.<ref name=KUO2006>{{cite journal|last1=Kuo|first1=Braden|last2=Urma|first2=Daniela|url=http://www.nature.com/gimo/contents/pt1/full/gimo6.html|title=Esophagus – anatomy and development|journal=GI Motility Online|date=2006|doi=10.1038/gimo6|doi-broken-date=12 July 2025}}</ref>

===Microanatomy===
{{Main|Gastrointestinal wall}}
{{multiple image
| align       = right
| image1      = Tinción hematoxilina-eosina.jpg
| width1      = 250
| alt1        = Histological section of the esophageal wall.
| caption1    = [[H&E]] stain of a [[biopsy]] of the normal esophageal wall, showing the wall's [[stratified squamous epithelium]] 
| image2      = Gastro-esophageal jxn.JPG
| width2      = 120
| alt2        = Histological section showing the gastroesophageal junction, with a black arrow pointing to the junction.
| caption2    = [[Histology|Histological]] section of the gastroesophageal junction, with a black arrow indicating the junction
| image3      = Histology of Esophagus.svg
| width3      = 130
| alt3        = Schematic diagram showing all the four layers of the wall of the Esophagus
| caption3    = [[Schematic]] diagram showing all the four layers of the wall of the Esophagus
| link3       = https://commons.wikimedia.org/wiki/File:Histology of Esophagus.svg
| perrow      = 1/2
| total_width = 400
}}
{{Gastrointestinal wall series}}
The human esophagus has a [[mucous membrane]] consisting of a tough [[stratified squamous epithelium]] without [[keratin]], a smooth [[lamina propria]], and a [[muscularis mucosae]].<ref name=KUO2006 /> The epithelium of the esophagus has a relatively rapid turnover and serves a protective function against the abrasive effects of food. In many animals, the epithelium contains a layer of keratin, representing a coarser diet.<ref name="ross">{{cite book|title=Histology: A Text and Atlas|url=https://archive.org/details/histologytextatl00ross|url-access=limited|publisher=Lippincott Williams & Wilkins|vauthors=Ross M, Pawlina W|year=2011|isbn=978-0-7817-7200-6|pages=[https://archive.org/details/histologytextatl00ross/page/n590 571]–73|edition=6th}}</ref> 

The [[muscular layer]] of the esophagus has two types of muscle. The upper third of the esophagus contains [[striated muscle]], the lower third contains [[smooth muscle]], and the middle third contains a mixture of both.<ref name=KUO2006 /> Muscle is arranged in two layers: one in which the muscle fibers run longitudinal to the esophagus, and the other in which the fibers encircle the esophagus. These are separated by the [[myenteric plexus]], a tangled network of nerve fibers involved in the secretion of mucus and in peristalsis of the smooth muscle of the esophagus. The outermost layer of the esophagus is the [[adventitia]] in most of its length, with the abdominal part being covered in [[serosa]]. This makes it distinct from many other structures in the gastrointestinal tract that only have a serosa.<ref name=KUO2006 />

====Glands====
There are two types of glands, with mucus-secreting [[esophageal gland]]s being found in the [[submucosa]] and esophageal cardiac glands, similar to [[cardiac glands]] of the stomach, located in the lamina propria and most frequent in the terminal part of the organ.<ref name="ross"/><ref>{{cite book|last=Takubo|first=Kaiyo|title=Pathology of the esophagus an .|date=2007|publisher=Springer Verlag|location=Tokyo|isbn=978-4-431-68616-3|page=28|edition=2nd}}</ref> The [[mucus]] from the glands gives a good protection to the lining.<ref>{{cite book|editor-first=Barbara|editor-last=Young|title=Wheater's functional histology: a text and colour atlas|url=https://archive.org/details/wheatersfunction00youn|url-access=limited|date=2006|publisher=Churchill Livingstone/Elsevier|isbn=978-0-443-06850-8|page=[https://archive.org/details/wheatersfunction00youn/page/n169 86]|edition=5th}}</ref> The submucosa also contains the [[submucosal plexus]], a network of [[neuron|nerve cells]] that is part of the [[enteric nervous system]].<ref name=ross />

==Development==
In early [[human embryogenesis|embryogenesis]], the esophagus develops from the [[endoderm]]al [[Primitive gut|primitive gut tube]]. The ventral part of the embryo abuts the [[yolk sac]]. It is very small in the beginning, but it lengthens due to descent of lungs and heart.<ref name="Chaurasia-2013a">{{Cite book|last=Chaurasia|first=B.D.|title=Human Anatomy|publisher=CBS Publishers and Distributors|year=2013|isbn=978-81-239-2331-4|edition=6th|volume=2|location=4819/XI, Prahlad Street, 24 Ansari Road, Daryaganj, New Delhi 110002, India|page=255|chapter=19}}</ref> During the second week of embryological development, as the embryo grows, it begins to surround parts of the sac. The enveloped portions form the basis for the adult gastrointestinal tract.<ref name=LARSEN2009 /> The sac is surrounded by a network of [[vitelline arteries]]. Over time, these arteries consolidate into the three main arteries that supply the developing gastrointestinal tract: the [[celiac artery]], [[superior mesenteric artery]], and [[inferior mesenteric artery]]. The areas supplied by these arteries are used to define the [[midgut]], [[hindgut]] and [[foregut]].<ref name=LARSEN2009 />

The surrounded sac becomes the primitive gut. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, such as the esophagus, [[stomach]], and [[intestine]]s.<ref name=LARSEN2009 /> The esophagus develops as part of the foregut tube.<ref name=LARSEN2009>{{cite book|author=Gary C. Schoenwolf|title=Larsen's human embryology|year=2009|publisher=Churchill Livingstone/Elsevier|location=Philadelphia|isbn=978-0-443-06811-9|chapter=Development of the Gastrointestinal Tract|edition=4th}}</ref> The esophagus develops as a tube, lined with [[smooth muscle]] but continues development [[craniocaudal]]ly into different proportions of [[striated muscle]]. Both types of muscle have been demonstrated to be of different precursor cells.<ref name="Rishniw">{{cite journal |last1=Rishniw |first1=M |last2=Rodriguez |first2=P |last3=Que |first3=J |last4=Burke |first4=ZD |last5=Tosh |first5=D |last6=Chen |first6=H |last7=Chen |first7=X |title=Molecular aspects of esophageal development. |journal=Annals of the New York Academy of Sciences |date=September 2011 |volume=1232 |issue=1 |pages=309–15 |doi=10.1111/j.1749-6632.2011.06071.x |pmid=21950820|pmc=3568516 |bibcode=2011NYASA1232..309R }}</ref>    The innervation of the esophagus develops from the [[pharyngeal arch]]es.<ref name=GRAYS2005 />

==Function==
===Swallowing===
Food is [[ingestion|ingested]] through the [[mouth]] and when [[swallowed]] passes first into the [[pharynx]] and then into the esophagus. The esophagus is thus one of the first components of the [[Digestion|digestive system]] and the [[human gastrointestinal tract|gastrointestinal tract]]. After food passes through the esophagus, it enters the stomach.<ref name=GUYTONHALL2005>{{cite book|last=Hall|first=Arthur C. Guyton, John E.|title=Textbook of medical physiology|year=2005|publisher=W.B. Saunders|location=Philadelphia|isbn=978-0-7216-0240-0|pages=782–784|edition=11th}}</ref> When food is being swallowed, the [[epiglottis]] moves backward to cover the [[larynx]], preventing food from entering the [[trachea]]. At the same time, the upper esophageal sphincter relaxes, allowing a [[Bolus (digestion)|bolus]] of [[food]] to enter. [[Peristalsis|Peristaltic]] contractions of the esophageal muscle push the food down the esophagus. These rhythmic contractions occur both as a reflex response to food that is in the mouth, and also as a response to the sensation of food within the esophagus itself. Along with peristalsis, the lower esophageal sphincter relaxes.<ref name=GUYTONHALL2005 />

===Reducing gastric reflux===
The stomach produces [[gastric juice]], a  mixture consisting of [[gastric acid]] (mainly [[hydrochloric acid]]), lipase, and pepsin to enable food [[digestion]].<ref name="Martinsen2019">{{cite journal |last1=Martinsen |first1=TC |last2=Fossmark |first2=R |last3=Waldum |first3=HL |title=The Phylogeny and Biological Function of Gastric Juice-Microbiological Consequences of Removing Gastric Acid. |journal=International Journal of Molecular Sciences |date=29 November 2019 |volume=20 |issue=23 |page=6031 |doi=10.3390/ijms20236031 |doi-access=free |pmid=31795477|pmc=6928904 }}</ref> Constriction of the lower esophageal sphincter protects the esophageal mucosa by preventing ''reflux'', the backflow of acid and gastric contents into the esophagus. The acute [[angle of His]] and the lower [[crura of the diaphragm]] also help this sphincteric action.<ref name=GUYTONHALL2005 /><ref>{{cite web|url=https://www.ncbi.nlm.nih.gov/books/NBK54272/|title=Neuromuscular Anatomy of Esophagus and Lower Esophageal Sphincter - Motor Function of the Pharynx, Esophagus, and its Sphincters - NCBI Bookshelf|publisher=Ncbi.nlm.nih.gov|date=2013-03-25|access-date=2013-04-24}}</ref>

==Gene and protein expression==
About 20,000 protein-coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal esophagus.<ref>{{Cite web|url=https://www.proteinatlas.org/humanproteome/esophagus|title=The human proteome in esophagus - The Human Protein Atlas|website=www.proteinatlas.org|access-date=2017-09-22}}</ref><ref>{{Cite journal|last1=Uhlén|first1=Mathias|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Lindskog|first4=Cecilia|last5=Oksvold|first5=Per|last6=Mardinoglu|first6=Adil|last7=Sivertsson|first7=Åsa|last8=Kampf|first8=Caroline|last9=Sjöstedt|first9=Evelina|date=2015-01-23|title=Tissue-based map of the human proteome|journal=Science|language=en|volume=347|issue=6220|article-number=1260419|doi=10.1126/science.1260419|issn=0036-8075|pmid=25613900|s2cid=802377}}</ref> Some 250 of these genes are more specifically expressed in the esophagus with less than 50 genes being highly specific. The corresponding esophagus-specific proteins are mainly involved in squamous differentiation such as [[keratin]]s [[Keratin 13|KRT13]], [[Keratin 4|KRT4]] and [[Keratin 6C|KRT6C]]. Other specific proteins that help lubricate the inner surface of esophagus are [[mucin]]s such as [[Mucin 21, cell surface associated|MUC21]] and MUC22. Many genes with elevated expression are also shared with skin and other organs that are composed of [[Epithelium|squamous epithelia]].<ref>{{Cite journal|last1=Edqvist|first1=Per-Henrik D.|last2=Fagerberg|first2=Linn|last3=Hallström|first3=Björn M.|last4=Danielsson|first4=Angelika|last5=Edlund|first5=Karolina|last6=Uhlén|first6=Mathias|last7=Pontén|first7=Fredrik|date=2014-11-19|title=Expression of Human Skin-Specific Genes Defined by Transcriptomics and Antibody-Based Profiling|journal=Journal of Histochemistry & Cytochemistry|language=en|volume=63|issue=2|pages=129–141|doi=10.1369/0022155414562646|pmid=25411189|pmc=4305515}}</ref>

==Clinical significance==
The main conditions affecting the esophagus are described here. For a more complete list, see [[esophageal disease]].

===Inflammation===
{{Main|Esophagitis}}
Inflammation of the esophagus is known as [[esophagitis]]. [[GERD|Reflux]] of [[gastric acid]]s from the stomach, infection, substances ingested (for example, [[corrosive substance|corrosives]]), some [[pharmaceutical drug|medications]] (such as [[bisphosphonate]]s), and [[food allergies]] can all lead to esophagitis. [[Esophageal candidiasis]] is an infection of the yeast ''[[Candida albicans]]'' that may occur when a person is [[immunocompromised]]. {{As of|2021}} the causes of some forms of esophagitis, such as [[eosinophilic esophagitis]], are not well-characterized, but may include [[Th2]]-mediated [[Atopy|atopies]] or genetic factors. There appear to be correlations between eosinophilic esophagitis, [[asthma]] (itself with an [[eosinophilic]] component), [[eczema]], and [[allergic rhinitis]], though it is not clear whether these conditions contribute to eosinophilic esophagitis or vice versa, or if they are symptoms of mutual underlying factors.<ref>{{Cite journal|last1=Arias|first1=Ángel|last2=Lucendo|first2=Alfredo J.|date=November 2020|title=Epidemiology and risk factors for eosinophilic esophagitis: lessons for clinicians|journal=Expert Review of Gastroenterology & Hepatology|volume=14|issue=11|pages=1069–1082|doi=10.1080/17474124.2020.1806054|issn=1747-4132|pmid=32749898|s2cid=220976044}}</ref> Esophagitis can cause [[Odynophagia|painful swallowing]] and is usually treated by managing the cause of the esophagitis - such as managing reflux or treating infection.<ref name=DAVIDSONS2010/>

===Barrett's esophagus===
{{Main|Barrett's esophagus}}
Prolonged esophagitis, particularly from gastric reflux, is one factor thought to play a role in the development of [[Barrett's esophagus]]. In this condition, there is [[metaplasia]] of the lining of the lower esophagus, which changes from [[stratified squamous epithelia]] to [[simple columnar epithelia]]. Barrett's esophagus is thought to be one of the main contributors to the development of [[esophageal cancer]].<ref name="DAVIDSONS2010" />

===Cancer===
{{Main|Esophageal cancer}}
There are two main types of [[Esophageal cancer|cancer of the esophagus]]. [[Squamous cell carcinoma]] is a [[carcinoma]] that can occur in the squamous cells lining the esophagus. This type is much more common in [[China]] and [[Iran]]. The other main type is an [[adenocarcinoma]] that occurs in the glands or columnar tissue of the esophagus. This is most common in [[developed countries]] in those with Barrett's esophagus, and occurs in the cuboidal cells.<ref name=DAVIDSONS2010 />

In its early stages, esophageal cancer may not have any symptoms at all. When severe, esophageal cancer may eventually cause obstruction of the esophagus, making swallowing of any solid foods very difficult and causing weight loss. The progress of the cancer is [[TNM staging|staged using a system]] that measures how far into the esophageal wall the cancer has invaded, how many [[lymph node]]s are affected, and whether there are any [[metastases]] in different parts of the body. Esophageal cancer is often managed with radiotherapy, chemotherapy, and may also be managed by [[esophagectomy|partial surgical removal of the esophagus]]. Inserting a [[esophageal stent|stent]] into the esophagus, or inserting a [[nasogastric tube]], may also be used to ensure that a person is able to digest enough food and water. {{As of|2014}}, the prognosis for esophageal cancer is still poor, so [[palliative therapy]] may also be a focus of treatment.<ref name=DAVIDSONS2010/>

===Varices===
{{Main|Esophageal varices}}
[[Esophageal varices]] are swollen twisted branches of the [[azygous vein]] in the lower third of the esophagus. These blood vessels [[anastomose]] (join up) with those of the [[portal vein]] when [[portal hypertension]] develops.<ref>{{cite book|last1=Albert|first1=Daniel|title=Dorland's illustrated medical dictionary|date=2012|publisher=Saunders/Elsevier|location=Philadelphia, PA|isbn=978-1-4160-6257-8|page=2025|edition=32nd}}</ref> These blood vessels are engorged more than normal, and in the worst cases may partially obstruct the esophagus. These blood vessels develop as part of a collateral circulation that occurs to drain blood from the [[abdomen]] as a result of [[portal hypertension]], usually as a result of [[liver disease]]s such as [[cirrhosis]].<ref name=DAVIDSONS2010/>{{rp|941–42}} This collateral circulation occurs because the lower part of the esophagus drains into the left gastric vein, which is a branch of the portal vein. Because of the extensive venous plexus that exists between this vein and other veins, if portal hypertension occurs, the direction of blood drainage in this vein may reverse, with blood draining from the portal venous system, through the plexus. Veins in the plexus may engorge and lead to varices.<ref name=KUO2006/><ref name=PATTI1997/>

Esophageal varices often do not have symptoms until they rupture. A ruptured varix is considered a medical emergency because varices can bleed a lot. A bleeding varix may cause a person [[haematemesis|to vomit blood]], or suffer [[shock (circulatory)|shock]]. To deal with a ruptured varix, a band may be placed around the bleeding blood vessel, or a small amount of a clotting agent may be injected near the bleed. A surgeon may also try to use a small inflatable balloon to apply pressure to stop the wound. [[IV fluids]] and [[blood product]]s may be given in order to prevent [[hypovolemia]] from excess blood loss.<ref name=DAVIDSONS2010 />

===Motility disorders===
Several disorders affect the motility of food as it travels down the esophagus. This can cause difficult swallowing, called [[dysphagia]], or painful swallowing, called [[odynophagia]]. [[Achalasia]] refers to a failure of the lower esophageal sphincter to relax properly, and generally develops later in life. This leads to progressive enlargement of the esophagus, and possibly eventual [[megaesophagus]]. A [[nutcracker esophagus]] refers to swallowing that can be extremely painful. [[Diffuse esophageal spasm]] is a spasm of the esophagus that can be one cause of chest pain. Such [[referred pain]] to the wall of the upper chest is quite common in esophageal conditions.<ref>{{cite book|last1=Purves|first1=Dale|title=Neuroscience|date=2011|publisher=Sinauer|location=Sunderland, Mass.|isbn=978-0-87893-695-3|page=214|edition=5.}}</ref> Sclerosis of the esophagus, such as with [[systemic sclerosis]] or in [[CREST syndrome]] may cause hardening of the walls of the esophagus and interfere with peristalsis.<ref name=DAVIDSONS2010 />

===Malformations===
[[Esophageal stricture]]s are usually benign and typically develop after a person has had [[GERD|reflux]] for many years. Other strictures may include [[esophageal web]]s (which can also be congenital) and damage to the esophagus by radiotherapy, corrosive ingestion, or eosinophilic esophagitis. A [[Schatzki ring]] is fibrosis at the gastroesophageal junction. Strictures may also develop in chronic [[anemia]], and [[Plummer-Vinson]] syndrome.<ref name=DAVIDSONS2010 />

Two of the most common [[congenital disorder|congenital]] malformations affecting the esophagus are an [[esophageal atresia]] where the esophagus ends in a blind sac instead of connecting to the stomach; and an [[tracheoesophageal fistula|esophageal fistula]] – an abnormal connection between the esophagus and the trachea.<ref name="Larsen">{{cite book|last1=Larsen|first1=William J.|title=Human embryology|date=2001|publisher=Churchill Livingstone|location=Philadelphia, Pa.|isbn=978-0-443-06583-5|pages=148–149|edition=3.}}</ref> Both of these conditions usually occur together.<ref name="Larsen"/> These are found in about 1 in 3500 births.<ref>{{cite journal|last=Shaw-Smith|first=C|title=esophageal atresia, tracheo-esophageal fistula, and the VACTERL association: review of genetics and epidemiology|journal=Journal of Medical Genetics|date=18 November 2005|volume=43|issue=7|pages=545–54|doi=10.1136/jmg.2005.038158|pmid=16299066|pmc=2564549}}</ref> Half of these cases may be part of a [[syndrome]] where other abnormalities are also present, particularly of the [[heart]] or [[limb (anatomy)|limb]]s. The other cases occur singly.<ref>{{cite journal|last1=Geneviève|first1=D|last2=de Pontual|first2=L|last3=Amiel|first3=J|last4=Sarnacki|first4=S|last5=Lyonnet|first5=S|title=An overview of isolated and syndromic oesophageal atresia.|journal=Clinical Genetics|date=May 2007|volume=71|issue=5|pages=392–9|pmid=17489843|doi=10.1111/j.1399-0004.2007.00798.x|s2cid=43782279}}</ref>

===Imaging===
[[File:Mid esophageal mass.jpg|thumbnail|A mass seen during an [[endoscopy]] and an [[medical ultrasound|ultrasound]] of the mass conducted during the endoscopy session]]
An [[X-ray]] of [[Barium swallow|swallowed barium]] may be used to reveal the size and shape of the esophagus, and the presence of any masses. The esophagus may also be [[medical imaging|imaged]] using a flexible camera inserted into the esophagus, in a procedure called an [[endoscopy]]. If an endoscopy is used on the stomach, the camera will also have to pass through the esophagus. During an endoscopy, a [[biopsy]] may be taken. If cancer of the esophagus is being investigated, other methods, including a [[CT scan]], may also be used.<ref name=DAVIDSONS2010 />

==History==
The word ''esophagus'' ([[British English]]: ''oesophagus''), comes from the {{langx|el|οἰσοφάγος}} ({{lang|grc-Latn|oisophagos}}) meaning ''gullet''. It derives from [[List of Greek and Latin roots in English#Oesophag-|two roots]] ''(eosin)'' to carry and ({{lang|grc-Latn|phagos}}) to eat.<ref name=Harper2014>{{cite web|last=Harper|first=Douglas|title=Esophagus|url=http://www.etymonline.com/index.php?term=esophagus&allowed_in_frame=0|work=Etymology Online|access-date=19 March 2014}}</ref> The use of the word esophagus, has been documented in anatomical literature since at least the time of [[Hippocrates]], who noted that "the oesophagus&nbsp;... receives the greatest amount of what we consume."<ref>{{cite book|author=Hippocrates|author-link=Hippocrates|title=Coan prenotions.|year=2010|publisher=Harvard University Press|location=Cambridge, Massachusetts|isbn=978-0-674-99640-3|edition=1. publ.|translator-last=Jones|translator-first=William Henry Samuel|page=[https://archive.org/details/hippocrates01hipp_0/page/59 59]|url=https://archive.org/details/hippocrates01hipp_0/page/59}}</ref> Its existence in other animals and its relationship with the [[stomach]] was documented by the [[Roman Empire|Roman]] [[naturalist]] [[Pliny the Elder]] (AD23–AD79),<ref>{{cite book|last=Bostock|first=John; Riley, Henry T.; Pliny the Elder|title=The natural history of Pliny|year=1855|publisher=H. G. Bohn|location=London|page=[https://archive.org/details/naturalhistoryof03plin/page/64 64]|url=https://archive.org/details/naturalhistoryof03plin}}</ref> and the [[peristalsis|peristaltic]] contractions of the esophagus have been documented since at least the time of [[Galen]].<ref>{{cite book|last=Brock|first=Galen; with an English translation by Arthur John|title=On the natural faculties|year=1916|publisher=W. Heinemann|location=London|isbn=978-0-674-99078-4|page="Book 3" S8|edition=Repr.|url=http://classics.mit.edu/Galen/natfac.3.three.html}}</ref>

The first attempt at surgery on the esophagus focused in the neck, and was conducted in dogs by [[Theodore Billroth]] in 1871. In 1877 [[Vincenz Czerny|Czerny]] carried out surgery in people. By 1908, an operation had been performed by Voeckler to remove the esophagus, and in 1933 the first surgical removal of parts of the lower esophagus, (to control [[esophageal cancer]]), had been conducted.<ref name=NORTON2008>{{cite book|editor-first=Jeffrey A.|editor-last=Norton|title=Surgery: basic science and clinical evidence|url=https://archive.org/details/surgerybasicscie00nort|url-access=limited|year=2008|publisher=Springer|location=New York, NY|isbn=978-0-387-30800-5|edition=2nd|pages=[https://archive.org/details/surgerybasicscie00nort/page/n757 744]–746}}</ref>

The [[Nissen fundoplication]], in which the stomach is wrapped around the lower [[esophageal sphincter]] to stimulate its function and control [[GERD|reflux]], was first conducted by [[Rudolph Nissen]] in 1955.<ref name=NORTON2008 />

==Other animals==
===Vertebrates===
{{Snake anatomy imagemap}}
{{Bile ducts and pancreas}}
In [[tetrapod]]s, the pharynx is much shorter, and the esophagus correspondingly longer, than in fish. In the majority of vertebrates, the esophagus is simply a connecting tube, but in some [[Bird anatomy|birds]], which regurgitate components to feed their young, it is extended towards the lower end to form a [[crop (anatomy)|crop]] for storing food before it enters the true stomach.<ref name=VB/><ref name=CA>{{cite book|last1=Hume|first2=C. Edward|last2=Stevens|first1=Ian D.|title=Comparative physiology of the vertebrate digestive system|year=2005|publisher=Cambridge University Press|location=Cambridge|isbn=978-0-521-61714-7|page=15|edition=1st pbk.}}</ref> In [[ruminant]]s, animals with four chambered stomachs, a groove called the ''sulcus reticuli'' is often found in the esophagus, allowing milk to drain directly into the hind stomach, the [[abomasum]].<ref>{{cite journal|last=Mackie|first=R. I.|title=Mutualistic Fermentative Digestion in the Gastrointestinal Tract: Diversity and Evolution|journal=Integrative and Comparative Biology|date=1 April 2002|volume=42|issue=2|pages=319–326|doi=10.1093/icb/42.2.319|pmid=21708724|doi-access=free}}</ref> In the [[horse]] the esophagus is about {{convert|4|to|5|ft|m|1|abbr=on|order=flip}} in length, and carries food to the stomach. A muscular ring, called the cardiac sphincter, connects the stomach to the esophagus. This sphincter is very well developed in horses. This and the oblique angle at which the esophagus connects to the stomach explains why horses cannot [[vomiting|vomit]].<ref name="Vet handbook">{{cite book|last1=Giffen|first1=James M.|first2=Tom|last2=Gore|title=Horse Owner's Veterinary Handbook|edition=2nd|location=New York|publisher=Howell Book House|orig-date=1989|year=1998|isbn=978-0-87605-606-6|url-access=registration|url=https://archive.org/details/horseownersveter0002giff}}</ref> The esophagus is also the area of the digestive tract where horses may have the condition known as [[choke (horse)|choke]].

The esophagus of [[snake]]s is remarkable for the distension it undergoes when swallowing prey.<ref>{{Cite journal|doi=10.1002/ar.22860|pmid=24482367|journal=Anat Rec|date=Mar 2014|volume=297|issue=3|pages=586–98|title=A model of the anterior esophagus in snakes, with functional and developmental implications|last1=Cundall|first1=D.|last2=Tuttman|first2=C.|last3=Close|first3=M.|s2cid=10921118|doi-access=free}}</ref>

In most fish, the esophagus is extremely short, primarily due to the length of the pharynx (which is associated with the [[gill]]s). However, some fish, including [[lamprey]]s, [[chimaera]]s, and [[lungfish]], have no true stomach, so that the esophagus effectively runs from the pharynx directly to the [[intestine]], and is therefore somewhat longer.<ref name=VB>{{cite book|author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977|title=The Vertebrate Body|publisher=Holt-Saunders International|location= Philadelphia, PA|pages= 344–345|isbn= 978-0-03-910284-5}}</ref>

In many vertebrates, the esophagus is lined by [[stratified squamous epithelium]] without glands. In fish, the esophagus is often lined with [[columnar epithelium]],<ref name=CA /> and in [[amphibian]]s, [[shark]]s and [[ray (fish)|rays]], the esophageal epithelium is [[cilia]]ted, helping to wash food along, in addition to the action of muscular peristalsis.<ref name=VB/> In addition, in the [[bat]] ''[[Plecotus auritus]]'', fish and some amphibians, glands secreting [[pepsinogen]] or [[hydrochloric acid]] have been found.<ref name=CA />

The muscle of the esophagus in many mammals is initially striated but then becomes smooth muscle in the caudal third or so. In [[canidae|canines]] and [[ruminant]]s, however, it is entirely striated to allow regurgitation to feed young (canines) or regurgitation to chew cud (ruminants). It is entirely smooth muscle in amphibians, reptiles and birds.<ref name=CA/>

Contrary to popular belief,<ref>{{cite news|last=Eveleth|first=Rose|author-link=Rose Eveleth|title=Could a Whale Accidentally Swallow You? It Is Possible|url=http://www.smithsonianmag.com/smart-news/could-a-whale-accidentally-swallow-you-it-is-possible-26353362/?no-ist|access-date=12 April 2014|newspaper=Smithsonian|date=20 February 2013}}</ref> an adult [[human body]] would not be able to pass through the esophagus of a [[whale]], which generally measures less than {{Convert|10|cm|in|sigfig=1|abbr=on|sp=us}} in diameter, although in larger [[baleen whale]]s it may be up to {{Convert|25|cm|in|sigfig=1|abbr=on|sp=us}} when fully distended.<ref>{{cite book|last=Tinker|first=Spencer Wilkie|title=Whales of the world|year=1988|publisher=E.J. Brill|location=Leiden|isbn=978-0-935848-47-2|page=60|url=https://books.google.com/books?id=ASIVAAAAIAAJ&q=how+long+is+a+whale%27s+esophagus&pg=PA60}}</ref>

===Invertebrates===
A structure with the same name is often found in invertebrates, including [[mollusc]]s and [[arthropod]]s, connecting the oral cavity with the stomach.<ref>{{cite journal|last=Hartenstein|first=Volker|title=Development of the insect stomatogastric nervous system|journal=Trends in Neurosciences|date=September 1997|volume=20|issue=9|pages=421–427|doi=10.1016/S0166-2236(97)01066-7|pmid=9292972|s2cid=22477083}}</ref> In terms of the [[Digestive system of gastropods|digestive system of snails and slugs]], the mouth opens into an esophagus, which connects to the stomach. Because of [[Torsion (gastropod)|torsion]], which is the rotation of the main body of the animal during larval development, the esophagus usually passes around the stomach, and opens into its back, furthest from the mouth. In species that have undergone de-torsion, however, the esophagus may open into the anterior of the stomach, which is the reverse of the usual gastropod arrangement.<ref name="Barnes1982">{{cite book|author= Barnes, Robert D.|year=1982|title= Invertebrate Zoology|publisher= Holt-Saunders International|location= Philadelphia, PA|isbn= 978-0-03-056747-6}}</ref> There is an extensive [[rostrum (anatomy)|rostrum]] at the front of the esophagus in all carnivorous snails and slugs.<ref name="Gerlach 1998">{{Cite journal|doi=10.1093/mollus/64.2.249|title=A first record of a terrestrial mollusc without a radula|year=1998|last1=Gerlach|first1=J.|last2=Van Bruggen|first2=A.C.|journal=Journal of Molluscan Studies|volume=64|issue=2|pages=249–250|doi-access=free}}</ref> In the freshwater snail species ''[[Tarebia granifera]]'', the brood pouch is above the esophagus.<ref name="Appleton 2009">Appleton C. C., Forbes A. T.& Demetriades N. T. (2009). [http://www.zoologischemededelingen.nl/83/nr03/a04 "The occurrence, bionomics and potential impacts of the invasive freshwater snail ''Tarebia granifera'' (Lamarck, 1822) (Gastropoda: Thiaridae) in South Africa"] {{Webarchive|url=https://web.archive.org/web/20140416180451/http://www.zoologischemededelingen.nl/83/nr03/a04|date=2014-04-16}}. ''Zoologische Mededelingen'' '''83'''.</ref>

In the [[cephalopod]]s, the brain often surrounds the esophagus.<ref>{{cite book|last1=Kutsch|first1=W|last2=Breidbach|first2=O|title=The nervous systems of invertebrates: an evolutionary and comparative approach|year=1994|publisher=Birkhäuser|location=Basel|isbn=978-3-7643-5076-5|page=117}}</ref>

==See also==
{{Anatomy-terms}}
{{Clear}}
==References==
{{Reflist}}

==External links==
{{Commons}}
{{Wiktionary|esophagus}}
{{Gastrointestinal tract}}
{{Human systems and organs}}
{{Viral systemic diseases}}
{{Digestive system procedures}}
{{Procedure templates}}
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