Page 59 - Clinical Anatomy

ECA1 7/18/06 6:31 PM Page 44

44 The Thorax

constricts it), the pericardium (separating it from the left atrium) and the
diaphragm.
Posteriorly lie the thoracic vertebrae, the thoracic duct, the azygos vein
and its tributaries and, near the diaphragm, the descending aorta.
On the left side it is related to the left subclavian artery, the terminal part
of the aortic arch, the left recurrent laryngeal nerve, the thoracic duct and
the left pleura. In the posterior mediastinum it relates to the descending
thoracic aorta before this passes posteriorly to the oesophagus above the
diaphragm.
On the right side there is the pleura and the azygos vein.
Below the root of the lung the vagi form a plexus on the oesophagus, the
left vagus lying anteriorly, the right posteriorly.
In the abdomen, passing forwards through the opening in the right
crus of the diaphragm, the oesophagus comes to lie in the oesophageal
groove on the posterior surface of the left lobe of the liver, covered by peri-
toneum on its anterior and left aspects. Behind it is the left crus of the
diaphragm.

Structure

The oesophagus is made of:
1◊◊an outer connective tissue sheath of areolar tissue;
2◊◊a muscular layer of external longitudinal and internal circular
fibres which are striated in the upper two-thirds and smooth in the lower
one-third;
3◊◊a submucous layer containing mucous glands;
4◊◊a mucosa of stratified epithelium passing abruptly into the columnar
epithelium of the stomach.
Blood supply is from the inferior thyroid artery, branches of the descend-
ing thoracic aorta and the left gastric artery. The veins from the cervical part
drain into the inferior thyroid veins, from the thoracic portion into the
azygos vein and from the abdominal portion partly into the azygos and
partly into the left gastric veins.
The lymphatic drainage is from a peri-oesophageal lymph plexus into the
posterior mediastinal nodes, which drain both into the supraclavicular
nodes and into nodes around the left gastric vessels. It is not uncommon to
be able to palpate hard, fixed supraclavicular nodes in patients with
advanced oesophageal cancer.
Radiographically, the oesophagus is studied by X-rays taken after a
barium swallow, in which it is seen lying in the retrocardiac space just in
front of the vertebral column. Anteriorly, the normal oesophagus is
indented from above downwards by the three most important structures
that cross it, the arch of the aorta, the left bronchus and the left atrium.

Clinical features

1◊◊For oesophagoscopy, measurements are made from the upper incisor