Esophagus

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The esophagus , or gullet is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. In humans the esophagus is continuous with the laryngeal part of the pharynx at the level of the C6 vertebra. It is a 5cm tube which connects the mouth to the stomach. The trachea branches off the esophagus to the lungs.

Functioning

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 lined with mucous membrane, and is more deeply lined with muscle that acts with peristaltic action to move swallowed food down to the stomach.

The swallowing sound that we hear is the esophagus functioning.

Histology

The layers of the esophagus are as follows:

• mucosa
• nonkeratinized stratified squamous epithelium: is rapidly turned over, and serves a protective effect due to the high volume transit of food, saliva and mucous.
• lamina propria: sparse.
• muscularecreting 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

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.

Esophageal diseases and conditions

Many people experience a burning sensation in their chest occasionally, caused by stomach acids refluxing into the esophagus, normally called heartburn. Extended exposure to heartburn may erode the lining of the esophagus, leading potentially to Barrett's esophagus which is associated an increased risk of adenocarcinoma most commonly found in the distal one-third of the esophagus.

Some people also experience a sensation known as globus esophagus, where it feels as if a ball is lodged in the lower part of the esophagus.

The following are additional diseases and conditions that affect the oesophagus:

• Achalasia
• Chagas disease
• Caustic injury to the esophagus
• Esophageal atresia and Tracheoesophageal fistula
• Esophageal cancer
• Esophageal web
• Esophagitis
• GERD
• Hiatus hernia
• Mallory-Weiss syndrome
• Neurogenic dysphagia
• Schatzki's ring
• Zenker's Diverticulum
• Boerhaave syndrome

Additional images

References

External links

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Last updated on Thursday March 13, 2008 at 20:48:24 PDT (GMT -0700)
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