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Esophagus: Location, Structure & Function
Esophagus: Location, Structure & Function
Includes labeled diagrams, downloadable notes, anatomy quizzes, and interactive learning tools
The esophagus is a muscular tube about 23-25 cm long that connects the pharynx to the stomach. It begins at the level of the sixth cervical vertebra, continues through the neck and thorax, passes through the diaphragm via the esophageal hiatus, and ends at the cardiac orifice of the stomach near the eleventh thoracic vertebra. The esophagus is divided into three parts: cervical part, thoracic part, and abdominal part.
Cervical Part
The cervical portion begins where the pharynx ends. It lies directly behind the trachea and in front of the cervical vertebrae and neck muscles.
Although it descends almost vertically, it shows a slight deviation to the left, which becomes more obvious lower down.
Thoracic Part
The thoracic portion is the longest part of the esophagus. It extends through the posterior mediastinum from the superior thoracic aperture to the diaphragm. It generally follows a vertical course but gradually shifts to the left.
At first it lies close to the vertebral column, but lower down it becomes separated from it by the aorta. It passes behind the left bronchus, lies against the posterior wall of the pericardium, and eventually crosses in front of the aorta before reaching the diaphragm.
Important relations include:
Right side: azygos vein
Posteriorly: thoracic duct
Closely associated with: vagus (pneumogastric) nerves
Abdominal Part
The abdominal portion is very short, measuring about 1 cm in length. After passing through the diaphragm, it turns slightly to the left and opens into the stomach at the cardiac orifice.
The esophagus follows a mainly vertical path but is not perfectly straight. It shows slight curves as it descends: it begins in the midline, deviates to the left in the neck, returns closer to the midline in the thorax, and again shifts to the left before entering the stomach.
It also follows the natural curves of the cervical and thoracic vertebral column.
The esophagus is not the same diameter throughout its length. It has several natural narrowings: especially at its beginning, where it is crossed by the left bronchus (often), and where it passes through the diaphragm. Between these constrictions are slight dilatations.
Food moves from the pharynx into the esophagus through the upper esophageal sphincter, which is continuous with the inferior pharyngeal constrictor.
Once food enters the esophagus, peristaltic waves propel it toward the stomach. Secretions from the esophageal mucosa lubricate both the wall and the food bolus during its passage.
Food enters the stomach through the lower esophageal sphincter (gastroesophageal or cardiac sphincter). This sphincter relaxes to allow food to pass and then contracts to prevent stomach contents from flowing back into the esophagus.
The diaphragm surrounding this region helps maintain closure when swallowing is not occurring.
If the sphincter does not close properly, stomach contents may reflux into the esophagus, producing heartburn or gastroesophageal reflux disease (GERD).
Wall of the Esophagus
The wall of the esophagus consists of several layers: the mucosa, submucosa, muscular layer, and the adventitia.
The mucosa is lined by non-keratinized stratified squamous epithelium, which protects the esophagus from abrasion caused by food particles.
The mucosa and submucosa contain mucus-secreting glands, which help lubricate the passageway. When the esophagus is empty, the mucous membrane forms longitudinal folds, and the lumen becomes very narrow.
The muscular wall contains an inner circular layer and an outer longitudinal layer. The muscle composition actually changes along its length:
Upper third: skeletal muscle
Middle third: mixed skeletal and smooth muscle
Lower third: smooth muscle
Additional muscle fibers may join the esophagus in the posterior mediastinum from the mediastinal pleura and the wall of the left bronchus.
Unlike the stomach and intestines, the esophagus is covered mainly by an adventitia rather than a serosa. This outer layer consists of loose connective tissue and is not covered by visceral peritoneum.
Need a recap? Take a look at the esophagus anatomy notes here.
Need a recap? Take a look at the esophagus anatomy notes here.
Ready to test what you've learned?
Play through the games below to test your understanding and sharpen your skills.
References
References
Gray, H. (1918). Anatomy of the human body (W. H. Lewis, Ed.; 20th ed.). Lea & Febiger.
Sobotta, J. (1906). Atlas and text-book of human anatomy (J. P. McMurrich, Ed.; W. H. Thomas, Trans.). Vol. 2. W.B. Saunders Company.
J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. (2013, April 25). Anatomy and Physiology. OpenStax. https://openstax.org/books/anatomy-and-physiology-2e/pages/23-3-the-mouth-pharynx-and-esophagus.
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
Image Credis
Image Credis
Images used in this guide and games are by Dr. Johannes Sobotta. They are in the public domain; modifications have been made to the originals.
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