Figure 42-2. Posterior view of cervical esophagus.

Abdominal Esophagus

The abdominal portion of the esophagus is approximately 3 to 6 cm long and consists of the abdominal

portion of the LES. It begins as the esophagus passes through the diaphragmatic hiatus and is

surrounded by the phrenoesophageal membrane, a fibroelastic ligament that arises from the

subdiaphragmatic fascia as a continuation of the transversalis fascia lining the abdomen (Fig. 42-3). The

upper leaf of the membrane attaches in a circumferential fashion around the esophagus about 1 to 2 cm

above the level of the hiatus. The lower leaf of the phrenoesophageal membrane blends with the serosa

of the stomach, and its end is marked anteriorly by a prominent fat pad, which corresponds

approximately with the gastroesophageal junction. The lower esophageal sphincter is a zone of high

pressure 3 to 4 cm long at the lower end of the esophagus

1 and does not correspond to any visible

macroscopic anatomic landmark either on the external surface of the esophagus, nor in the endoscopic

appearance of the mucosa. Its function is derived from the microscopic architecture of the muscle fibers.

The esophageal hiatus is surrounded by the right and left crura, which together form a sling of

diaphragmatic skeletal muscle around the esophagus that originates from tendinous bands attached to

the anterolateral surface of the first lumbar vertebra (Fig. 42-4). The relative contribution of the right

and left crura to this sling is variable. Posterior to the esophagus, the crura are united by a tendinous

arch, the median arcuate ligament, which lies just anterior to the aorta.

Figure 42-3. Anatomy of the esophageal hiatus and relationship to the phrenoesophageal membrane.

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Figure 42-4. Inferior view of diaphragm and anatomy of the esophageal hiatus.

Structure of the Esophageal Wall and Mucosa

The esophagus is composed of three primary layers – mucosa, submucosa, and muscularis propria. The

mucosal layer is normally composed of nonkeratinized stratified squamous epithelium, as opposed to

the stomach where columnar epithelium is present. In the distal aspect of the esophagus within the

lower esophageal sphincter, repeated exposure of the squamous epithelium to gastric contents can result

in metaplasia of esophageal squamous mucosa to a columnar epithelium called cardiac mucosa. This

nomenclature was originally used to describe what was mistakenly thought to be the proximal stomach

or cardia, but there is now convincing evidence that this is in fact metaplastic esophageal mucosa.2 With

further injury and exposure to refluxed gastric juice such as bile acids, cardiac mucosa may further

transform into intestinal metaplasia or Barrett esophagus, characterized by the presence of goblet cells

within cardiac mucosa. Alternatively, cardiac mucosa can also differentiate further to acquire parietal

cells and is known as oxyntocardiac mucosa.3

A critical layer within the mucosa for determining the biologic behavior of a superficial cancer is the

muscularis mucosa. This thin, poorly developed layer lies below the basement membrane and above the

submucosa. It is often duplicated in patients with Barrett esophagus, and can lead to confusion during

pathologic evaluation of the depth of tumor invasion in endoscopic resection (ER) specimens.4 The

significance of the muscularis mucosa is that tumors confined to this layer rarely are associated with

lymph node metastases, but once tumors penetrate through this layer into the submucosa the frequency

of lymph node metastases increases substantially.

The submucosa is characterized by a rich lymphatic plexus that extends throughout the esophagus.

Lymphatic collecting branches arise from within the submucosa and pierce the muscularis propria to

communicate with regional lymph nodes and the thoracic duct outside of the esophagus. This network

of lymphatics allow for significant longitudinal spread of esophageal cancers and a high rate of skip

metastases. Clinically, tumor invasion beyond the muscularis mucosa into the submucosa is significant

due to this lymphatic system, with the rate of regional lymph node metastases increasing from <5%

with intramucosal tumors to 20% to 50% for submucosal tumors.5 Finally, the submucosa of the

esophagus also harbors mucous glands that drain into the lumen. These glands are helpful for

determining the true extent of the esophagus when metaplasia of the mucosa occurs.

The muscularis propria is composed of an inner circular layer and an outer longitudinal layer. The

muscles are striated in the upper portion and transition to completely smooth muscle near the upper

third of the esophagus. The longitudinal muscle layer courses down in an elongated spiral pattern,

turning approximately 90 degrees as it descends to the stomach. The circular muscle layer is thicker

than the longitudinal layer, which also takes on an elliptical or spiral orientation (Fig. 42-5). This

arrangement of muscle is responsible for the wormlike drive of peristalsis.

Blood Supply, Lymphatics, and Innervation

The cervical portion of the esophagus receives its main blood supply from the inferior thyroid artery.

The thoracic portion receives blood from the bronchial and esophageal arteries. Seventy-five percent of

individuals have one right-sided and two left-sided bronchial arteries, and usually two esophageal

branches arise directly from the aorta. There are rarely aortic branches directly to the esophagus in the

lower half of the esophagus in the chest, allowing the surgeon to perform an en bloc dissection of all of

the periesophageal tissue directly off the plane of the aortic adventitia from the right to the left pleural

spaces. The blood supply of the abdominal portion of the esophagus comes from the ascending branch of

the left gastric artery and from the right and left inferior phrenic arteries (Fig. 42-6). After the vessels

have entered the muscular wall of the esophagus, branching occurs at right angles to provide an

extensive longitudinal vascular plexus. The rich blood supply provided by this vascular plexus allows

mobilization of the esophagus from the stomach to the aortic arch without causing ischemic injury.6

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Figure 42-5. Endoscopic view of esophageal muscle layers during a peroral endoscopic myotomy (POEM) for achalasia. The

endoscopic knife is lifting and cutting the circumferential circular muscle fibers, leaving the longitudinal muscle fibers intact.

Figure 42-6. Arterial anatomy of the esophagus.

The capillaries of the esophagus drain into a submucosal and periesophageal venous plexus, from

which the esophageal veins originate. In the cervical region, the esophageal veins empty into the

inferior thyroid vein; in the thoracic region, they empty into the bronchial, azygos, or hemiazygos

veins; and in the abdominal region, they empty into the coronary vein (Fig. 42-7).

The lymphatic channels are located almost exclusively below the muscularis mucosa in the submucosa

of the esophagus, constituting a dense and interconnected plexus with more lymph vessels than blood

capillaries (Fig. 42-8). Lymph flow in the submucosal plexus runs in a longitudinal direction, and after

the injection of a contrast medium, the longitudinal spread is six times that of the transverse spread. In

the upper two-thirds of the esophagus, the lymphatic flow is mostly cephalad; in the lower third, it is

mostly caudal. In the thoracic portion of the esophagus, the submucosal lymph plexus extends over a

long distance in a longitudinal direction before penetrating the muscle layer to enter lymph vessels in

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the adventitia. As a consequence of this nonsegmental lymph drainage, the lymphatic spread of tumor

cells can extend for a considerable distance superiorly and inferiorly within the submucosal lymphatics

before the cells pass through lymphatic channels in the muscularis and on into the regional lymph

nodes. There is a high rate of skip metastases in esophageal cancer due to this arrangement. By contrast,

the cervical esophagus has a more segmental lymph drainage into the regional lymph nodes, and as a

result, tumors in this portion of the esophagus have less submucosal extension.

Lymph from the cervical esophagus drains into the paratracheal and deep cervical lymph nodes,

whereas lymph from the upper thoracic esophagus flows mainly into the paratracheal lymph nodes. The

lymph from the lower thoracic esophagus drains into the subcarinal and inferior pulmonary nodes.

Lymph from the distal thoracic and abdominal portion of the esophagus drains into the parahiatal and

perigastric nodes.7

Figure 42-7. Venous anatomy of the esophagus.

The parasympathetic innervation of the pharynx and esophagus is provided mainly by cranial nerve X

or the vagus nerves. The constrictor muscles of the pharynx receive branches from the pharyngeal

plexus, which is located on the posterior lateral surface of the middle constrictor muscle and is formed

by pharyngeal branches of the vagus nerve, with a small contribution from cranial nerves IX and XI.

The cricopharyngeal sphincter and the cervical portion of the esophagus receive branches from both the

right and left recurrent laryngeal nerves originating from the vagus nerves (Fig. 42-9). Damage to these

recurrent nerves interferes not only with the movement of the vocal cords but also with the function of

the cricopharyngeal sphincter and the motility of the cervical esophagus, predisposing the patient to

pulmonary aspiration on swallowing. The upper thoracic esophagus receives innervation from the left

recurrent laryngeal nerve and both vagus nerves. As the right and left vagus nerves descend into the

mediastinum, they join the outer surface of the esophagus. The esophageal plexus, which is formed by

the branches of the right and left vagus nerves and thoracic sympathetic chain, lies on the anterior and

posterior walls of the esophagus and innervates the lower thoracic portion.8 The branches of the plexus

coalesce into the left (anterior) and right (posterior) vagal trunks.

Afferent visceral sensory fibers from the esophagus end without synapse in the first four segments of

the thoracic spinal cord by a combination of sympathetic and vagal pathways. These pathways are also

occupied by afferent visceral sensory fibers from the heart, which explains the similarity of symptoms in

esophageal and cardiac diseases.

PHYSIOLOGY

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