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The esophagus (
American English American English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. English is the most widely spoken language in the United States and in most circumstances ...
) or oesophagus (
British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, "English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in England, or, more broadl ...
; both ), non-technically known also as the food pipe or gullet, is an
organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an electronic keyboard instrument ** Hammond ...
in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the stomach. The esophagus is a fibromuscular tube, about long in adults, that travels behind the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
and
heart The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
, passes through the
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
, and empties into the uppermost region of the stomach. During swallowing, the
epiglottis The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
tilts backwards to prevent food from going down the larynx and lungs. The word ''oesophagus'' 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 outwards consists of mucosa,
submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and j ...
(connective tissue), 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 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 sphincters 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 nerves via the sympathetic trunk and parasympathetic nerves 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 passes through the thoracic cavity into the
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
into the stomach. The esophagus may be affected by gastric reflux,
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
, prominent dilated blood vessels called varices that can bleed heavily, 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 X-rays when swallowing barium sulfate, endoscopy, and CT scans. Surgically, the esophagus is difficult to access in part due to its position between critical organs and directly between the sternum and spinal column.


Structure

The esophagus is one of the upper parts of the digestive system. There are taste buds on its upper part. It begins at the back of the mouth, passing downward through the rear part of the mediastinum, through the
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
, and into the stomach. In humans, the esophagus generally starts around the level of the sixth cervical vertebra behind the
cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
of the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
, enters the diaphragm at about the level of the
tenth thoracic vertebra In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
, and ends at the
cardia The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach is ...
of the stomach, at the level of the
eleventh thoracic vertebra In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
. The esophagus is usually about 25 cm (10 in) in length. Many
blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide awa ...
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 arteries In human anatomy, the bronchial arteries supply the lungs with nutrition and oxygenated blood. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung and are a vital part ...
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 The inferior phrenic arteries are two small vessels which supply the diaphragm. They present much variety in their origin. Structure Origin The inferior phrenic arteries usually arise between T12 and L2 vertebrae. They may arise separately ...
. The venous drainage also differs along the course of the esophagus. The upper and middle parts of the esophagus drain into the azygos and hemiazygos veins, 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. Lymphatically, the upper third of the esophagus drains into the deep cervical lymph nodes, the middle into the superior and posterior mediastinal lymph nodes, and the lower esophagus into the 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. ;Position The upper esophagus lies at the back of the mediastinum behind the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
, adjoining along the
tracheoesophageal stripe The tracheoesophageal stripe is formed by the posterior wall of the trachea and the anterior wall of the esophagus. This line is best identified on the lateral chest x-ray. When this line is greater than 5 mm it is considered abnormal. The m ...
, and in front of the erector spinae muscles and the vertebral column. The lower esophagus lies behind the
heart The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
and curves in front of the thoracic aorta. From the 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. 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 veins and the intercostal veins on the right side. The vagus nerve divides and covers the esophagus in a
plexus In neuroanatomy, a plexus (from the Latin term for "braid") is a branching network of vessels or nerves. The vessels may be blood vessels (veins, capillaries) or lymphatic vessels. The nerves are typically axons outside the central nervous system ...
. ;Constrictions 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: * At the start of the esophagus, where the laryngopharynx joins the esophagus, behind the
cricoid cartilage The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
* 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
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
in the posterior mediastinum


Sphincters

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. These sphincters 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 The cricoid cartilage , or simply cricoid (from the Greek ''krikoeides'' meaning "ring-shaped") or cricoid ring, is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment si ...
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. The upper esophageal sphincter surrounds the upper part of the esophagus. It consists of skeletal muscle but is not under voluntary control. Opening of the upper esophageal sphincter is triggered by the
swallowing reflex Swallowing, sometimes called deglutition in scientific contexts, is the process in the human or animal body that allows for a substance to pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. Swallowing is ...
. The primary muscle of the upper esophageal sphincter is the cricopharyngeal part of the inferior pharyngeal constrictor. The lower esophageal sphincter, or gastroesophageal sphincter, surrounds the lower part of the esophagus at the junction between the esophagus and the stomach. It is also called the cardiac sphincter or cardioesophageal sphincter, named from the adjacent part of the stomach, the ''
cardia The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach is ...
''. Dysfunction of the gastroesophageal sphincter causes gastroesophageal reflux, which causes heartburn, and, if it happens often enough, can lead to gastroesophageal reflux disease, with damage of the esophageal mucosa.


Nerve supply

The esophagus is innervated by the vagus nerve and the cervical and thoracic sympathetic trunk. The vagus nerve has a 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 The nucleus ambiguus ("ambiguous nucleus" in English) is a group of large motor neurons, situated deep in the medullary reticular formation named by Jacob Clarke. The nucleus ambiguus contains the cell bodies of neurons that innervate the muscle ...
, whereas fibers that supply the smooth muscle and lower esophageal sphincter have bodies situated in the
dorsal motor nucleus The dorsal nucleus of vagus nerve (or posterior nucleus of vagus nerve or dorsal vagal nucleus or nucleus dorsalis nervi vagi or nucleus posterior nervi vagi) is a cranial nerve nucleus for the vagus nerve in the medulla that lies ventral to the fl ...
. The vagus nerve plays the primary role in initiating peristalsis. The sympathetic trunk has a 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. 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.


Gastro-esophageal junction

The gastro-esophageal junction (also known as the esophagogastric junction) is the junction between the esophagus and the stomach, at the lower end of the esophagus. The pink color of the esophageal mucosa contrasts to the deeper red of the gastric mucosa, and the mucosal transition can be seen as an irregular zig-zag line, which is often called the z-line. Histological examination reveals abrupt transition between the stratified squamous epithelium of the esophagus and the simple columnar epithelium of the stomach. Normally, the
cardia The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach is ...
of the stomach is immediately distal to the z-line 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 Barrett's esophagus is a condition in which there is an abnormal ( metaplastic) change in the mucosal cells lining the lower portion of the esophagus, from stratified squamous epithelium to simple columnar epithelium with interspersed goblet cells ...
the true gastro-eshophageal junction can be identified by the upper limit of the gastric folds rather than the mucosal transition. The functional location of the lower oesophageal sphincter is generally situated about below the z-line.


Microanatomy

The human esophagus has a mucous membrane consisting of a tough stratified squamous epithelium without
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up Scale (anatomy), scales, hair, Nail ...
, a smooth lamina propria, and a
muscularis mucosae The lamina muscularis mucosae (or muscularis mucosae) is a thin layer ( lamina) of muscle of the gastrointestinal tract, located outside the lamina propria, and separating it from the submucosa. It is present in a continuous fashion from the e ...
. 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. There are two types of glands, with mucus-secreting esophageal glands being found in the
submucosa The submucosa (or tela submucosa) is a thin layer of tissue in various organs of the gastrointestinal, respiratory, and genitourinary tracts. It is the layer of dense irregular connective tissue that supports the mucosa (mucous membrane) and j ...
and esophageal cardiac glands, similar to
cardiac glands The gastric glands are glands in the lining of the stomach that play an essential role in the process of digestion. All of the glands have mucus-secreting foveolar cells. Mucus lines the entire stomach, and protects the stomach lining from the ef ...
of the stomach, located in the lamina propria and most frequent in the terminal part of the organ. The
mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...
from the glands gives a good protection to the lining. The submucosa also contains the submucosal plexus, a network of
nerve cells A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...
that is part of the enteric nervous system. 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. 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.


Development

In early embryogenesis, the esophagus develops from the endodermal primitive gut tube. The ventral part of the embryo abuts the
yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...
. 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. 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. 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 intestines. The esophagus develops as part of the foregut tube. The innervation of the esophagus develops from the pharyngeal arches.


Function


Swallowing

Food is 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 digestive system and the gastrointestinal tract. After food passes through the esophagus, it enters the stomach. When food is being swallowed, the
epiglottis The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food in ...
moves backward to cover the larynx, preventing food from entering the
trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...
. At the same time, the upper esophageal sphincter relaxes, allowing a bolus of food to enter.
Peristaltic Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whic ...
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.


Reducing gastric reflux

The stomach produces gastric acid, a strongly acidic mixture consisting of hydrochloric acid (HCl) and
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
and
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
salts to enable food digestion. Constriction of the upper and lower esophageal sphincters helps to prevent reflux (backflow) of gastric contents and acid into the esophagus, protecting the esophageal mucosa. The acute angle of His and the lower
crura of the diaphragm The crus of diaphragm (pl. crura), refers to one of two tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction. They take their ...
also help this sphincteric action.


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. 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 Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up Scale (anatomy), scales, hair, Nail ...
s KRT13, KRT4 and
KRT6C Keratin 6C (protein name K6C; gene name ''KRT6C''), is a type II cytokeratin, one of a number of isoforms of keratin 6 encoded by separate genes located within the type II keratin gene cluster on human chromosome 12q. This gene was uncovered recent ...
. Other specific proteins that help lubricate the inner surface of esophagus are mucins such as MUC21 and MUC22. Many genes with elevated expression are also shared with skin and other organs that are composed of
squamous epithelia Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
.


Clinical significance

The main conditions affecting the esophagus are described here. For a more complete list, see esophageal disease.


Inflammation

Inflammation of the esophagus is known as
esophagitis Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stomach; ...
. Reflux of gastric acids from the stomach, infection, substances ingested (for example, corrosives), some medications (such as bisphosphonates), 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. the causes of some forms of esophagitis, such as eosinophilic esophagitis, are not well-characterized, but may include
Th2 The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are considere ...
-mediated atopies or genetic factors. There appear to be correlations between eosinophilic esophagitis,
asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...
(itself with an eosinophilic component),
eczema Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved c ...
, and
allergic rhinitis Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, ...
, though it is not clear whether these conditions contribute to eosinophilic esophagitis or vice versa, or if they are symptoms of mutual underlying factors. Esophagitis can cause painful swallowing and is usually treated by managing the cause of the esophagitis - such as managing reflux or treating infection.


Barrett's esophagus

Prolonged esophagitis, particularly from gastric reflux, is one factor thought to play a role in the development of
Barrett's esophagus Barrett's esophagus is a condition in which there is an abnormal ( metaplastic) change in the mucosal cells lining the lower portion of the esophagus, from stratified squamous epithelium to simple columnar epithelium with interspersed goblet cells ...
. In this condition, there is metaplasia of the lining of the lower esophagus, which changes from
stratified squamous epithelia A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural i ...
to simple columnar epithelia. Barrett's esophagus is thought to be one of the main contributors to the development of esophageal cancer.


Cancer

There are two main types of 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 China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
and
Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
. 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. 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 staged using a system that measures how far into the esophageal wall the cancer has invaded, how many lymph nodes are affected, and whether there are any
metastases Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...
in different parts of the body. Esophageal cancer is often managed with radiotherapy, chemotherapy, and may also be managed by partial surgical removal of the esophagus. Inserting a stent into the esophagus, or inserting a
nasogastric tube Nasogastric intubation is a medical process involving the insertion of a plastic tube (nasogastric tube or NG tube) through the nose, down the oesophagus, and down into the stomach. Orogastric intubation is a similar process involving the inserti ...
, may also be used to ensure that a person is able to digest enough food and water. , the prognosis for esophageal cancer is still poor, so
palliative therapy Palliative care (derived from the Latin root , or 'to cloak') is an interdisciplinary medical caregiving approach aimed at optimizing quality of life and mitigating suffering among people with serious, complex, and often terminal illnesses. Wit ...
may also be a focus of treatment.


Varices

Esophageal varices are swollen twisted branches of the
azygous vein The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for bloo ...
in the lower third of the esophagus. These blood vessels anastomose (join up) with those of the portal vein when portal hypertension develops. 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 diseases such as cirrhosis. 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. 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 to vomit blood, or suffer
shock Shock may refer to: Common uses Collective noun *Shock, a historic commercial term for a group of 60, see English numerals#Special names * Stook, or shock of grain, stacked sheaves Healthcare * Shock (circulatory), circulatory medical emerge ...
. 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 Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...
and blood products may be given in order to prevent hypovolemia from excess blood loss.


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 Diffuse esophageal spasm (DES), also known as distal esophageal spasm, is a condition characterized by uncoordinated contractions of the esophagus, which may cause difficulty swallowing (dysphagia) or regurgitation. In some cases, it may cause sym ...
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. 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.


Malformations

Esophageal stricture A benign esophageal stricture, or peptic stricture, is a narrowing or tightening of the esophagus that causes swallowing difficulties. Signs and symptoms Symptoms of esophageal strictures include heartburn, bitter or acid taste in the mouth, chok ...
s are usually benign and typically develop after a person has had reflux for many years. Other strictures may include esophageal webs (which can also be congenital) and damage to the esophagus by radiotherapy, corrosive ingestion, or eosinophilic esophagitis. A Schatzki ring is fibrosis at the gastro-esophageal junction. Strictures may also develop in chronic anemia, and Plummer-Vinson syndrome. Two of the most common 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 esophageal fistula – an abnormal connection between the esophagus and the trachea. Both of these conditions usually occur together. These are found in about 1 in 3500 births. Half of these cases may be part of a syndrome where other abnormalities are also present, particularly of the
heart The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
or
limb Limb may refer to: Science and technology * Limb (anatomy), an appendage of a human or animal *Limb, a large or main branch of a tree *Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb *Limb, in botany, ...
s. The other cases occur singly.


Imaging

An X-ray of 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 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.


History

The word ''esophagus'' (
British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, "English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in England, or, more broadl ...
: ''oesophagus''), comes from the el, οἰσοφάγος () meaning ''gullet''. It derives from two roots ''(eosin)'' to carry and () to eat. The use of the word oesophagus, has been documented in anatomical literature since at least the time of
Hippocrates Hippocrates of Kos (; grc-gre, Ἱπποκράτης ὁ Κῷος, Hippokrátēs ho Kôios; ), also known as Hippocrates II, was a Greek physician of the classical period who is considered one of the most outstanding figures in the history o ...
, who noted that "the oesophagus ... receives the greatest amount of what we consume." Its existence in other animals and its relationship with the stomach was documented by the
Roman Roman or Romans most often refers to: * Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lett ...
naturalist Pliny the Elder (AD23–AD79), and the
peristaltic Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, whic ...
contractions of the esophagus have been documented since at least the time of Galen. The first attempt at surgery on the esophagus focused in the neck, and was conducted in dogs by
Theodore Billroth Christian Albert Theodor Billroth (26 April 18296 February 1894) was a German surgeon and amateur musician. As a surgeon, he is generally regarded as the founding father of modern abdominal surgery. As a musician, he was a close friend and conf ...
in 1871. In 1877 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. The Nissen fundoplication, in which the stomach is wrapped around the lower
esophageal sphincter The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...
to stimulate its function and control reflux, was first conducted by Rudolph Nissen in 1955.


Other animals


Vertebrates

In tetrapods, 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 birds, which regurgitate components to feed their young, it is extended towards the lower end to form a crop for storing food before it enters the true stomach. In ruminants, animals with four stomachs, a groove called the ''sulcus reticuli'' is often found in the esophagus, allowing milk to drain directly into the hind stomach, the abomasum. In the horse the esophagus is about 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 vomit. The esophagus is also the area of the digestive tract where horses may have the condition known as choke. The esophagus of snakes is remarkable for the distension it undergoes when swallowing prey. In most fish, the esophagus is extremely short, primarily due to the length of the pharynx (which is associated with the gills). However, some fish, including lampreys, chimaeras, and lungfish, have no true stomach, so that the esophagus effectively runs from the pharynx directly to the intestine, and is therefore somewhat longer. In many vertebrates, the esophagus is lined by stratified squamous epithelium without glands. In fish, the esophagus is often lined with columnar epithelium, and in amphibians,
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...
s and rays, the esophageal epithelium is ciliated, helping to wash food along, in addition to the action of muscular peristalsis. In addition, in the bat '' Plecotus auritus'', fish and some amphibians, glands secreting pepsinogen or hydrochloric acid have been found. The muscle of the esophagus in many mammals is initially striated but then becomes smooth muscle in the caudal third or so. In canines and ruminants, 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. Contrary to popular belief, an adult human body would not be able to pass through the esophagus of a whale, which generally measures less than in diameter, although in larger baleen whales it may be up to when fully distended.


Invertebrates

A structure with the same name is often found in invertebrates, including molluscs and
arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s, connecting the oral cavity with the stomach. In terms of the digestive system of snails and slugs, the mouth opens into an esophagus, which connects to the stomach. Because of 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. There is an extensive rostrum at the front of the esophagus in all carnivorous snails and slugs. In the freshwater snail species '' Tarebia granifera'', the brood pouch is above the esophagus.Appleton C. C., Forbes A. T.& Demetriades N. T. (2009)
"The occurrence, bionomics and potential impacts of the invasive freshwater snail ''Tarebia granifera'' (Lamarck, 1822) (Gastropoda: Thiaridae) in South Africa"
. ''Zoologische Mededelingen'' 83.
In the cephalopods, the brain often surrounds the esophagus.


See also


References


External links

{{Authority control Digestive system Thorax (human anatomy) Organs (anatomy) Human head and neck Abdomen