Oesophagus

The oesophagus (plural: oesophagi or oesophaguses) is a muscular tube that conveys food and fluids from the pharynx to the stomach. It forms part of the upper gastrointestinal tract.

Gross anatomy

The oesophagus is 23-37 cm long with a diameter of 1-2 cm and is divided into three parts:

• cervical: continuous with the hypopharynx, commences at the lower border of cricoid cartilage (at level of C5/6) or cricopharyngeus muscle

• thoracic: from superior thoracic aperture (T1) to the oesophageal hiatus (T10) in the diaphragm which covers the inferior thoracic aperture

• abdominal: from oesophageal hiatus and is continuous with the cardia of the stomach at the gastro-oesophageal junction

The cervical oesophagus begins at the upper oesophageal sphincter, which is formed by the cricopharyngeus muscle ⁶.

The oesophagus then descends to the left of the midline through the neck and superior mediastinum, returning to the midline at T5, before coursing to the left of the midline once more, in the posterior mediastinum. The distal thoracic oesophagus then curves anteriorly to pass through the diaphragm into the abdominal cavity. 

The lower oesophageal sphincter, a specialised region of the circular muscle of the distal oesophagus, manifests itself radiographically as the phrenic ampulla (a.k.a. oesophageal vestibule), a 2-4 cm long dilatation between the A-ring and B-ring ⁶.

There are three normal oesophageal constrictions that should not be confused for pathological constrictions:

• cervical constriction (narrowest point): due to the cricoid cartilage at the level of C5/6

• thoracic constriction: due to the aortic arch at the level of T4/5

• abdominal constriction: at the oesophageal hiatus at the level of T10/11

Relations

• posteriorly: vertebral column; pre-vertebral fascia; descending aorta; thoracic duct (at thoracic plane); accessory hemiazygos and hemiazygos veins (at T8/9)

• anteriorly: trachea (to T4/5); recurrent laryngeal nerves (in tracheo-oesophageal groove); left main bronchus; left atrium

• left lateral: lung; pleura; aorta; left subclavian artery; thoracic duct

• right lateral: lung; pleura; azygos vein

Arterial supply

• upper third: inferior thyroid artery

• middle third: oesophageal branches of the thoracic aorta and by the bronchial arteries

• lower third: oesophageal branches of the left gastric artery

Venous drainage

• upper third: inferior thyroid veins to brachiocephalic veins

• middle third: azygos vein to SVC

• lower third: left gastric vein to portal vein (site of portal-systemic collateral pathway)

Lymphatic drainage

Follows arterial supply:

• upper third: deep cervical lymph nodes

• middle third: posterior mediastinal lymph nodes

• lower third: left gastric and coeliac group lymph nodes

However it is important to note that within the oesophageal walls, there are lymphatic channels which enable lymph to pass for long distances. Therefore, drainage may not necessarily follow any strict pattern.

Innervation

• sympathetic trunk (sympathetic fibres)

• vagal trunk (parasympathetic fibres)

Histology

The oesophagus is made up of five layers, noting there is no serosal layer. From outer to inner, these are:

• adventitia

• muscularis propria

  • outer longitudinal muscularis propria

  • inner circular muscularis propria (in the upper one-third of the oesophagus this layer is composed of striated (voluntary) muscle while the lower two-thirds is smooth muscle)

• submucosa

• mucosa

  • stratified squamous epithelium that abruptly changes to columnar epithelium in the lower oesophagus

Variant anatomy

Majority of the anatomical variations of the oesophagus are congenital, typically occurring at time of separation from the trachea (around third to seventh weeks intrauterine)

• oesophageal bronchus

• oesophageal atresia

• oesophageal diverticulum (congenital variant is typically rare)

• aberrant right subclavian artery passing anterior or posterior to the oesophagus

Radiographic appearance

Fluoroscopy

• modified barium swallow is used to evaluate pharyngeal motility during swallowing; the procedure utilises barium of varying consistencies given by mouth with video recording of swallowing

• barium swallow is the main radiological method of assessing the oesophagus; double contrast oesophagogram using CO₂ gas-forming crystals and barium contrast are used to distend the oesophagus and coat the mucosa

Ultrasound

Endoscopic ultrasonography is used for evaluation of the depth of the oesophageal tumour.

CT

• 80% will contain gas allowing for appreciation of the wall if there is enough surrounding mediastinal fat

• if collapsed will appear as round or ovoid

MRI

• T1: isointense to muscle

• T2: hyperintense to muscle

Nuclear medicine

PET-CT

Useful for the staging of oesophageal cancer.

Related pathology

• neoplastic

  • oesophageal cancer

  • benign oesophageal neoplasms

• non-neoplastic

  • presbyoesophagus

  • hiatus hernia

  • achalasia

    • corkscrew oesophagus

  • gastro-oesophageal reflux disease

    • feline oesophagus

  • oesophageal rupture

    • Boerhaave syndrome

  • oesophageal stricture

    • oesophageal web

    • Schatzki ring

see also

• Oesophageal duplication

• Oesophageal diverticulum

• A ring (oesophagus)