Oesophagus: Course, Constrictions and Gastro-oesophageal Junction

Course and structure

The oesophagus runs from the lower border of the cricoid cartilage at C6 to the cardia of the stomach at about T11, in three parts.

• Cervical: from C6 to the thoracic inlet, behind the trachea and slightly to the left of the midline.
• Thoracic: through the superior and posterior mediastinum. It returns towards the midline in the upper chest, then curves forward and to the left to reach the diaphragm.
• Abdominal: a short segment below the oesophageal hiatus, covered by peritoneum in front and on its left, lying in a groove on the back of the left lobe of the liver.

Its wall has mucosa of non-keratinised stratified squamous epithelium, a submucosa with mucous glands, and a muscular coat of inner circular and outer longitudinal layers. The muscle is skeletal in the upper third, mixed in the middle third and smooth in the lower third. There is no serosa above the diaphragm.

Constrictions

The lumen is narrowed at four points, which is where swallowed objects lodge and where strictures and tumours are looked for at endoscopy.

Gastro-oesophageal junction

The gastro-oesophageal junction lies to the left of the midline at about T11, behind the seventh left costal cartilage, where the tubular oesophagus opens into the cardia. On the inside the pale squamous lining meets the redder gastric columnar mucosa at an irregular line, the Z-line.

There is no thick anatomical sphincter. Reflux is prevented by several factors together:

• the lower oesophageal sphincter, a zone of tonically contracted circular smooth muscle;
• the right crus of the diaphragm, which encircles the hiatus and pinches it on inspiration;
• the acute angle of His between the oesophagus and the fundus;
• positive intra-abdominal pressure on the abdominal segment;
• the phreno-oesophageal ligament, which anchors the junction to the hiatus.

Beyond the junction the stomach is divided into the cardia, fundus (above the level of the junction), body, pyloric antrum, pyloric canal and pylorus, whose thickened circular muscle forms the pyloric sphincter.

Relations

Throughout its course the oesophagus lies in front of the vertebral column and behind the airway and then the heart.

• Neck: the trachea in front, with the recurrent laryngeal nerves in the grooves between trachea and oesophagus; the thyroid lobes and carotid sheaths at the sides; the prevertebral fascia behind.
• Superior mediastinum: the trachea in front, the aortic arch on the left and the azygos vein arching on the right, the thoracic duct behind and to the left.
• Posterior mediastinum: the left main bronchus, then the pericardium over the left atrium in front; the descending aorta behind and to the left below; the azygos vein and thoracic duct behind on the right.
• At the diaphragm: the vagal trunks lie on its surface as it passes through the right crus.

Blood supply and innervation

Each third of the oesophagus takes its blood from the nearest regional vessels. The upper third is supplied by the inferior thyroid arteries, the middle third by oesophageal branches of the thoracic aorta and bronchial arteries, and the lower third by oesophageal branches of the left gastric artery and the left inferior phrenic artery.

Venous drainage follows the same pattern: inferior thyroid veins above, azygos and hemiazygos veins in the thorax, and the left gastric vein, a portal tributary, at the lower end. This makes the lower oesophagus a portosystemic anastomosis.

Lymph drains to deep cervical nodes above, posterior mediastinal nodes in the middle, and left gastric and coeliac nodes below, although lymphatics in the submucosa run long distances.

The striated upper part is supplied by the recurrent laryngeal nerves. Below the lung roots the vagi form the oesophageal plexus, which regroups as the anterior vagal trunk, mainly from the left vagus, and the posterior vagal trunk, mainly from the right. Sympathetic fibres come from the sympathetic trunks and greater splanchnic nerves.

Clinical relevance

The constrictions, the lower-end venous anastomosis and the reflux barrier account for most oesophageal disease tested in the anatomy viva.

• Oesophageal varices: in portal hypertension the left gastric to azygos anastomosis dilates and can bleed torrentially.
• Hiatus hernia: in a sliding hernia the junction moves up into the chest; in a rolling (para-oesophageal) hernia the fundus rolls up beside a junction that stays in place.
• Carcinoma: squamous cell carcinoma is more frequent in the upper and middle thirds; adenocarcinoma arises in the lower third, often in Barrett's oesophagus, where columnar mucosa has replaced squamous.
• Boerhaave syndrome: spontaneous rupture after forceful vomiting, usually of the lower left posterolateral wall.
• Pharyngeal pouch: a pulsion diverticulum through Killian's dehiscence, between thyropharyngeus and cricopharyngeus, just above the oesophagus.
• Oesophageal web: a thin mucosal ring in the upper oesophagus, seen on barium swallow as a narrow filling defect.

On the specimen

This station shows the lower oesophagus opened in continuity with the stomach, and asks for each part from the gastro-oesophageal junction to the pyloric sphincter.

• Oesophagus: a narrow tube with pale, smooth mucosa and longitudinal folds.
• Gastro-oesophageal junction: the irregular line where pale oesophageal lining meets the redder, thicker gastric mucosa.
• Cardia: the small zone of stomach immediately around the junction.
• Fundus: the dome that rises above the level of the junction, under the left dome of the diaphragm.
• Body: the large central part, lined by prominent rugae.
• Pyloric antrum and canal: the antrum widens after the angular incisure and narrows into the short pyloric canal.
• Pyloric sphincter: the thick, palpable ring of circular muscle at the gastroduodenal junction.

The station also uses a barium swallow showing a circumferential ring in the upper oesophagus with dilatation above it, a partial obstruction such as a web.