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Esophagus
Head and neck.
Digestive organs. (Esophagus is #1)
Latin	œsophagus
Gray's	subject #245 1144
Artery	esophageal arteries
Vein	esophageal veins
Nerve	celiac ganglia, vagus[1]
Precursor	Foregut
MeSH	oesophagus
Dorlands/Elsevier	Esophagus

The esophagus or oesophagus (see spelling differences), sometimes 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 (οισοφάγος), lit. "entrance for eating." In humans the esophagus is continuous with the laryngeal part of the pharynx at the level of the C6 vertebra. The esophagus passes through a hole in the level of the tenth thoracic vertebrae (T10). It is usually about 25–30 cm long and connects the mouth to the stomach. It is divided into abdominal parts.

[edit] Functions of the esophagus

Food is passed through the esophagus by using the process of peristalsis. Specifically, it connects the pharynx, which is the body cavity that is common to the digestive factory and respiratory system, with the stomach, where the second stage of digestion is initiated.

The esophagus is deeply lined with food down in the stomach. Due to the fact that the esophagus lacks mucus lining like that of the stomach, it can get irritated by stomach acid that passes the cardiac sphincter.

[edit] Histology

The layers of the esophagus are as follows:^[2]

• mucosa (mucus)
  • nonkeratinized stratified squamous epithelium: is rapidly turned over, and serves a protective effect due to the high volume transit of food, saliva and mucus.
  • lamina propria: sparse.
  • muscularis mucosae: smooth muscle
• submucosa: Contains the mucous secreting glands (esophageal glands), and connective structures termed papillae.
• muscularis externa (or "muscularis propria"): composition varies in different parts of the esophagus, to correspond with the conscious control over swallowing in the upper portions and the autonomic control in the lower portions:
  • upper third, or superior part: striated muscle
  • middle third, smooth muscle and striated muscle
  • inferior third: predominantly smooth muscle
• adventitia

[edit] Gastroesophageal junction

The junction between the esophagus and the stomach (the gastroesophageal junction or GE junction) is not actually considered a valve, although it is sometimes called the cardiac sphincter, cardia or cardias, but is actually more of a stricture.

[edit] In other animals

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 oesophagus effectively runs from the pharynx directly to the intestine, and is therefore somewhat longer.^[3]

In tetrapods, which have lost the gills, the pharynx is much shorter, and the oesophagus correspondingly longer, than in fish. In amphibians, sharks and rays, the oesophageal epithelium is ciliated, helping to wash food along, in addition to the action of muscular peristalsis. In the majority of vertebrates, the oesophagus 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.

[edit] See also

• Esophageal disease

[edit] Additional images

H&E stain of biopsy of normal esophagus showing the stratified squamous cell epithelium	Layers of the esophagus.	Mid-esophageal mass	Stomach
Accessory digestive system.	Organs of the digestive tract.	Esophagus	Section of the neck at about the level of the sixth cervical vertebra.
Transverse section of thorax, showing relations of pulmonary artery.	Sagittal section of nose mouth, pharynx, and larynx.	The position and relation of the esophagus in the cervical region and in the posterior mediastinum. Seen from behind. |	Section of the human esophagus. Moderately magnified.
Microscopic shot of a cross section of human gastroesophageal junction wall.

[edit] References

[edit] External links

Look up esophagus in Wiktionary, the free dictionary.

• Virtual Slidebox at Univ. Iowa Slide 449