Esophagus

 

Esophagus

Thoracic Part

The esophagus is a tubular structure about 10 in. (25 cm) long that is continuous above with the laryngeal part of the pharynx opposite the sixth cervical vertebra. It passes through the diaphragm at the level of the 10th thoracic vertebra to join the stomach. In the neck, the esophagus lies in front of the vertebral column; laterally, it is related to the lobes of the thyroid gland; and anteriorly, it is in contact with the trachea and the recurrent laryngeal nerves. In the thorax, it passes downward and to the left through the superior and then the posterior mediastinum. At the level of the sternal angle, the aortic arch pushes the esophagus over to the midline.

Relations

The relations of the thoracic part of the esophagus from above downward are as follows-

Anteriorly- The trachea and the left recurrent laryngeal nerve the left principal bronchus which constricts it and the pericardium which separates the esophagus from the left atrium

Posteriorly- The bodies of the thoracic vertebrae; the thoracic duct; the azygos veins; the right posterior intercostals arteries; and, at its lower end, the descending thoracic aorta

Right side: The mediastinal pleura and the terminal part of the azygos vein

Left side: The left subclavian artery, the aortic arch, the thoracic duct, and the mediastinal pleura inferiorly to the level of the roots of the lungs, the vagus nerves leave the pulmonary plexus and join with sympathetic nerves to form the esophageal plexus.

The left vagus lies anterior to the esophagus, and the right vagus lies posterior. At the opening in the diaphragm, the esophagus is accompanied by the two vagi, branches of the left gastric blood vessels, and lymphatic vessels. Fibers from the right crus of the diaphragm pass around the esophagus in the form of a sling.

In the abdomen, the esophagus descends for about 0.5 in. (1.3 cm) and then enters the stomach. It is related to the left lobe of the liver anteriorly and to the left crus of the diaphragm posteriorly.

 

Blood Supply

Arteries-The upper third of the esophagus is supplied by the inferior thyroid artery, the middle third by branches from the descending thoracic aorta, and the lower third by branches from the left gastric artery.

Veins- The veins from the upper third drain into the inferior thyroid veins, from the middle third into the azygos veins, and from the lower third into the left gastric vein, a tributary of the portal vein

Nerve Supply

The esophagus is supplied by parasympathetic and sympathetic efferent and afferent fibers via the vagi and sympathetic trunks. In the lower part of its thoracic course, the esophagus is surrounded by the esophageal nerve plexus.

Esophagus

Abdominal Part

The esophagus enters the abdomen through an opening in the right crus of the diaphragm. After a course of about 0.5 in. (1.25 cm), it enters the stomach on its right side.

Relations- The esophagus is related anteriorly to the posterior surface of the left lobe of the liver and posteriorly to the left crus of the diaphragm. The left and right vagi lie on its anterior and posterior surfaces, respectively.

Blood Supply

Arteries- The arteries are branches from the left gastric artery.

Veins-The veins drain into the left gastric vein, a tributary of the portal vein.

Nerve Supply- The nerve supply is the anterior and posterior gastric nerves (vagi) and sympathetic branches of the thoracic part of the sympathetic trunk.

Functions

The esophagus conducts food from the pharynx into the stomach. Wave like contractions of the muscular coat, called peristalsis, propel the food onward.

Gastroesophageal Sphincter

No anatomic sphincter exists at the lower end of the esophagus. However, the circular layer of smooth muscle in this region serves as a physiologic sphincter. As the food descends through the esophagus, relaxation of the muscle at the lower end occurs ahead of the peristaltic wave so that the food enters the stomach. The tonic contraction of this sphincter prevents the stomach contents from regurgitating into the esophagus. The closure of the sphincter is under vagal control and this can be augmented by the hormone gastrin and reduced in response to secretin, cholecystokinin, and glucagon.