esophagus

esophagus, portion of the digestive tube that conducts food from the mouth to the stomach. When food is swallowed it passes from the pharynx into the esophagus, initiating rhythmic contractions (peristalsis) of the esophageal wall, which propel the food along toward the stomach. The walls of the esophagus are lined with mucous glands that continue the lubrication of the food as it is conducted to the stomach. The human esophagus is about 10 in. (25 cm) long and 1 in. (2.5 cm) in diameter. See digestive system.

Muscular tube that conveys food by peristalsis from the pharynx to the stomach. Both ends are closed off by sphincters (muscular constrictions), which relax to let food through and close to keep it from backing up. Disorders include ulceration and bleeding, heartburn from stomach acid, achalasia (failure of one or both sphincters to open), and muscle spasms. Scleroderma may involve the esophagus.

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The esophagus or oesophagus (see American and British English 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 oesophagus, which derives from the Greek word oisophagos (οισοφάγος). 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 thoracic diaphragm called the esophageal hiatus. It is usually 25-30 cm long which connects the mouth to the stomach. It is divided into cervical, thoracic, and abdominal parts.

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

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 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

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.

See also

• Esophageal disease

Additional images

References

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