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Esophagus

Surgical Anatomy:

The esophagus is a muscular tube that starts as the continuation of pharynx. It is about 25cm in length and at the cardia of the stomach. It begins from the 6th cervical vertebrae laterally and anteriorly from the cricoid cartilage. The cervical part is about 5.6 cm in length and lies in front of the vertebral column, laterally it is related to the lobes of thyroid cartilage. Anteriorly it is in contact with trachea and recurrent laryngeal nerve.
After, anterior to the thoracic cavity where it is about 20-21 cm in length, it passes downwards and to the left through the superior and then posterior mediastinum. At the level of the sternal angle, the aortic arch pushes the esophagus over to the midline. Relations in the thoracic cavity are:

Anterior: trachea, left recurrent laryngeal nerve, left bronchus, pericardium that separates it from the left atrium.
Posterior: the bodies of thoracic vertebrae, the thoracic duct, the azygos veins, descending thoracic aorta.
Right: mediastinal pleura and terminal part of the azygos veins.
Left: subclavian artery, aortic arch and thoracic duct.

The esophagus lies in the midline, with a deviation to the left side in the lower portion of neck and upper portion of the thorax, returns to the midline in the midportion of thorax near the bifurcation of the trachea, while entering the diaphragm it again deviates to the left side anterior to the thoracic duct.
The third part is the abdominal part, which is about 1-2 cm.

Narrowings:
There are three narrowings of esophagus:
  1. First narrowing is located at the entrance into esophagus caused by the cricopharyngeal muscles. Its diameter is about 1.5 cm and is upper narrowing of esophagus.
  2. Second narrowing is due to an indentation of the anterior and left lateral esophageal wall caused by crossing of left main stem bronchus and aortic arch. Lumen diameter is about 1.5 to 1.6 cm.
  3. 3rd narrowing is at the level of diaphragm, which is caused by gastro esophageal sphincter mechanism. Lumen diameter is about 1.6 to 1.9 cm.
Muscles:
Muscular layer of esophagus contains two types of muscles:
  1. Striated muscles: the upper 2-6 cm of esophagus contains only striated muscle fibers, where shutter mechanism occur and it has V shape.
  2. Smooth muscles which are of two types: inner circular and outer longitudinal. By stretching and relaxing of these muscles there is worm like propulsion of food.
The longitudinal muscle fibers originate from a cricopharyngeal tendon arising from the dorsal upper edge of anteriorly located cricoid cartilage. The circular muscular layer of esophagus is thicker than the outer longitudinal layer.

Before entering the diaphragm, distal portion of esophagus is covered with phrenoesophageal membrane (2-3 cm), which has the greatest importance in the action of cardiac sphincter. Phrenoesophageal membrane is the fibroelastic ligament arising from subdiaphragmatic fascia as a continuation of the fascia transversalis lining the abdomen.

Mucous membrane of esophagus (3/4) is represented with flat epithelium but the little dorsal part is represented with glandular or columnar epithelium.

Blood Supply:
Despite of other blood supply, esophagus has segmental character, blood enters to the sub mucous layer and they form T-shaped connection between them.

The upper part receives blood from inferior thyroid artery i.e. surgical interventions in patients who has gone under thyroidectomy is quite difficult and complicated. The thoracic portion is aggregated from bronchial branches of thoracic aorta and the inferior portion from esophageal branches of thoracic aorta but the lowermost portion is supplied by phrenic branches and left gastric arteries.

Venous Drainage:
In the upper portion, the blood drains into the inferior thyroid veins. In the thoracic portion blood drains into bronchial and esophageal veins, azygos and hemiazygos veins on the anterior surface of vertebral column (Between them passes thoracic duct). From the distal part blood drains into phrenic and left gastric veins. In the distal part of esophagus so called portal anastomosis occur. In the submucosal layer we have quite important portal caval anastomosis. (Black Moore’s tube is used to stop the bleeding from this site).

Lymph Drainage:
There are several groups of lymphatics. Paraesophageal nodes and internal jugular nodes, then distally paratracheal nodes. In the thoracic cavity are pulmonary Hilar nodes and subcarinal nodes. Lymph vessels from upper third of the esophagus drain into deep cervical nodes. From thoracic portion drain into superior and posterior mediastinal nodes. From distal portion drain into the left gastric nodes, splenic nodes which are connected with the celiac nodes and hepatic nodes. Malignancy produced can be spread via these lymph nodes through the whole length of esophagus. That is why it is important that when the malignant tumor occurs, resection may be performed in quite a large area.

Nerve Supply:
Esophagus receives vagal nerve (parasympathetic) but sympathetic from thoracic sympathetic chain

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This article has been written by Dr. M. Javed Abbas.
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20:59 21/12/2002