The Oesophagus

Anatomical Course

The oesophagus begins in the neck, at the level of C6. Here, it is continuous superiorly with the laryngeal part of the pharynx (the laryngopharynx).

It descends downward into the superior mediastinum of the thorax, positioned between the trachea and the vertebral bodies of T1 to T4. It then enters the abdomen via the oesophageal hiatus (an opening in the right crus of the diaphragm) at T10.

The abdominal portion of the oesophagus is approximately 1.25cm long – it terminates by joining the cardiac orifice of the stomach at level of T11.

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Anatomical Structure

The oesophagus shares a similar structure with many of the organs in the alimentary tract:

• Adventitia – outer layer of connective tissue.
  • Note: The very distal and intraperitoneal portion of the oesophagus has an outer covering of serosa, instead of adventitia.
• Muscle layer – external layer of longitudinal muscle and inner layer of circular muscle. The external layer is composed of different muscle types in each third:
  • Superior third – voluntary striated muscle
  • Middle third – voluntary striated and smooth muscle
  • Inferior third – smooth muscle
• Submucosa
• Mucosa – non-keratinised stratified squamous epithelium (contiguous with columnar epithelium of the stomach).

Food is transported through the oesophagus by peristalsis – rhythmic contractions of the muscles which propagate down the oesophagus.

Adapted from work by Cancer Research UK [CC BY-SA 4.0]

Fig 2
The layers of the oesophagus. The muscle layer is further divided into an outer longitudinal layer and inner circular layer.

Oesophageal Sphincters

There are two sphincters present in the oesophagus, known as the upper and lower oesophageal sphincters. They act to prevent the entry of air and the reflux of gastric contents respectively.

Upper Oesophageal Sphincter

The upper sphincter is an anatomical, striated muscle sphincter at the junction between the pharynx and oesophagus. It is produced by the cricopharyngeus muscle. Normally, it is constricted to prevent the entrance of air into the oesophagus.

Lower Oesophageal Sphincter

The lower oesophageal sphincter is located at the gastro-oesophageal junction (between the stomach and oesophagus). The gastro-oesophageal junction is situated to the left of the T11 vertebra, and is marked by the change from oesophageal to gastric mucosa.

The sphincter is classified as a physiological (or functional) sphincter, as it does not have any specific sphincteric muscle. Instead, the sphincter is maintained by four factors:

• Oesophagus enters the stomach at an acute angle.
• Walls of the intra-abdominal section of the oesophagus are compressed when there is a positive intra-abdominal pressure.
• Prominent mucosal folds at the gastro-oesophageal junction aid in occluding the lumen.
• Right crus of the diaphragm has a “pinch-valve” effect.

During oesophageal peristalsis, the sphincter is relaxed to allow food to enter the stomach. Otherwise at rest, the function of this sphincter is to prevent the reflux of acidic gastric contents into the oesophagus.

Anatomical Relations

The anatomical relations of the oesophagus give rise to four physiological constrictions in its lumen – it is these areas where food/foreign objects are most likely to become impacted. They can be remembered using the acronym ‘ABCD‘:

• Arch of aorta
• Bronchus (left main stem)
• Cricoid cartilage
• Diaphragmatic hiatus

The table below lists the anatomical relations of the oesophagus:

Vasculature

The vascular supply of the oesophagus is segmental – reflecting its division into cervical, thoracic, and abdominal parts.

Cervical 

The cervical oesophagus receives its arterial supply from branches of the inferior thyroid artery (arising from the thyrocervical trunk).

Venous drainage occurs via the inferior thyroid veins into the brachiocephalic veins.

Thoracic

The thoracic oesophagus is supplied primarily by oesophageal branches of the thoracic aorta, with additional contributions from the bronchial arteries.

Venous drainage is via the azygos and hemiazygos veins, which empty into the systemic circulation.

Abdominal

The abdominal oesophagus is supplied by branches of the left gastric artery (from the coeliac trunk) and the left inferior phrenic artery.

Venous drainage occurs via two routes:

• Into the portal circulation via left gastric vein
• Into the systemic circulation via the azygous vein.

These two routes form a porto-systemic anastomosis – a connection between the portal and systemic venous systems.

By TeachMeSeries Ltd (2026)

Fig 3
Posterior view of the oesophagus. Some of the thoracic vasculature is noted.

Innervation

The oesophagus is innervated by the oesophageal plexus, which is formed by a combination of the parasympathetic vagal trunks and sympathetic fibres from the cervical and thoracic sympathetic trunks.

Two different types of nerve fibre run in the vagal trunks. The upper oesophageal sphincter and upper striated muscle is supplied by fibres originating from the nucleus ambiguus. Fibres supplying the lower oesophageal sphincter and smooth muscle of the lower oesophagus arise from the dorsal motor nucleus.

Lymphatics

The lymphatic drainage of the oesophagus is divided into thirds:

• Superior third – deep cervical lymph nodes.
• Middle third – superior and posterior mediastinal nodes.
• Lower third – left gastric and celiac nodes.

Clinical Relevance

Disorders of the Oesophagus

Barrett’s Oesophagus

Barrett’s oesophagus refers to the metaplasia (reversible change from one differentiated cell type to another) of the lower oesophageal epithelium. In this condition, the normal non-keratinised stratified squamous epithelium is replaced by specialised intestinal-type columnar epithelium.

This change is most commonly caused by chronic gastro-oesophageal reflux, due to incompetence of the lower oesophageal sphincter. Repeated exposure to acidic gastric contents leads to epithelial injury and subsequent metaplastic adaptation.

Barrett’s oesophagus is diagnosed via endoscopy with biopsy. It is a premalignant condition, associated with an increased risk of developing oesophageal adenocarcinoma. Patients are therefore enrolled in surveillance programmes to monitor for dysplastic or malignant change.

Oesophageal Carcinoma

Oesophageal carcinoma accounts for a small proportion of malignancies in the UK. There are two major histological types of oesophageal carcinoma:

• Squamous cell carcinoma – can occur at any level of the oesophagus, but is more common in the upper and middle thirds. It is associated with risk factors such as smoking and alcohol use.
• Adenocarcinoma – usually arises in the lower third of the oesophagus and is associated with Barrett’s oesophagus and chronic gastro-oesophageal reflux. In Western populations, this is now the more common subtype.

The most common clinical features are:

• Dysphagia – typically progressive, initially to solids and later to liquids
• Weight loss
• Odynophagia (pain on swallowing)

Oesophageal carcinoma carries a poor prognosis, largely due to its late presentation.

Oesophageal Varices

The abdominal oesophagus drains into both the systemic and portal circulation, forming an anastomosis between the two.

Oesophageal varices are abnormally dilated sub-mucosal veins (in the wall of the oesophagus) that lie within this anastomosis. They are usually produced when the pressure in the portal system increases beyond normal, a state known as portal hypertension. Portal hypertension most commonly occurs secondary to chronic liver disease, such as cirrhosis or an obstruction in the portal vein.

The varices are predisposed to bleeding, with most patients presenting with haematemesis (vomiting of blood). Alcoholics are at a high risk of developing oesophageal varices.

By TeachMeSeries Ltd (2026)

Fig 4
Endoscopic view of oesophageal varices