Esophagus

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Esophagus
Illu01 head neck.jpg
The esophagus relations to pharynx and mouth
BauchOrgane wn.png
Digestive organs (esophagus is #1)
LatinEsophagus
Gray'ssubject #245 1144
SystemPart of the digestive System
ArteryEsophageal arteries
VeinEsophageal veins
NerveCeliac ganglia, vagus[1]
PrecursorForegut
MeSHEsophagus
Dorlands/ElsevierEsophagus
 
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Esophagus
Illu01 head neck.jpg
The esophagus relations to pharynx and mouth
BauchOrgane wn.png
Digestive organs (esophagus is #1)
LatinEsophagus
Gray'ssubject #245 1144
SystemPart of the digestive System
ArteryEsophageal arteries
VeinEsophageal veins
NerveCeliac ganglia, vagus[1]
PrecursorForegut
MeSHEsophagus
Dorlands/ElsevierEsophagus

The esophagus (oesophagus, commonly known as the gullet) is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. The word esophagus is derived from the Latin œsophagus, which derives from the Greek word oisophagos, lit. "entrance for eating."

In animals, food is ingested through the mouth. During swallowing, food passes from the mouth through the pharynx into the esophagus. The epiglottis folds down to a more horizontal position so as to prevent food from going into the trachea, instead directing it to the esophagus. Once in the esophagus, the bolus travels down to the stomach via rhythmic contraction and relaxation of muscles known as peristalsis.

In humans the esophagus is continuous with the laryngeal part of the pharynx at the level of the C6 vertebra. The esophagus passes through posterior mediastinum in the thorax and enters abdomen through a hole in the diaphragm at the level of the tenth thoracic vertebrae (T10). It is usually about 25cm, but extreme variations have been recorded ranging 10–50 cm long depending on individual height. It is divided into cervical, thoracic and abdominal parts. Due to the inferior pharyngeal constrictor muscle, the entry to the esophagus opens only when swallowing or vomiting.

Histology[edit]

Course of the esophagus (anterior view), showing it passing posteriorly to the trachea and the heart.

The layers of the oesophagus are as follows:[2]

Similar to rectum, it lacks serosa

Esophageal constrictions[edit]

Normally, the esophagus has three anatomic constrictions at the following levels:

The distances from the incisor teeth are important as is useful for diagnostic endoscopic procedures.

Esophageal sphincters[edit]

At rest, the esophagus is closed at both ends by the upper esophageal sphincter (UES) at the top, and the lower esophageal sphincter (LES) at the bottom.

The junction between the esophagus and the stomach (the gastroesophageal junction or GE junction) is controlled by the lower esophageal sphincter (LES), which remains constricted at all times other than during swallowing and vomiting to prevent the contents of the stomach from entering the esophagus. As the esophagus does not have the same protection from acid as the stomach, any failure of the LES can lead to heartburn.

Peristalsis[edit]

In the esophagus, as in much of the gastrointestinal tract, smooth muscles contract in sequence to produce a peristaltic wave which forces a ball of food (called a bolus) down and through the LES into the stomach.

In other animals[edit]

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.[3]

In tetrapods, the pharynx is much shorter, and the esophagus correspondingly longer, than in fish. In amphibians, sharks and rays, the esophageal epithelium is ciliated, helping to wash food along, in addition to the action of muscular peristalsis. In the majority of vertebrates, the esophagus is simply a connecting tube, but in birds, it is extended towards the lower end to form a crop for storing food before it enters the true stomach.[3]

A structure with the same name is often found in invertebrates, including molluscs and arthropods, connecting the oral cavity with the stomach.

See also[edit]

Additional images[edit]

References[edit]

  1. ^ Physiology at MCG 6/6ch2/s6ch2_30
  2. ^ BU Histology Learning System: 10801loa
  3. ^ a b Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 344–345. ISBN 0-03-910284-X. 

External links[edit]