H) Oesophagus

The oesophagus is a hollow viscous that connects the pharynx to the stomach.


The oesophagus is a muscular tube, about 25 cm in length, which is continuous with the laryngopharynx superiorly and the stomach inferiorly. It begins at the inferior border of the cricoid cartilage and C6; the gastro-oesophageal junction usually lies at T11. It is typically considered in three parts, based on the body cavities it runs through:

  • The cervical oesophagus, most superior of the three, begins at the junction with the laryngopharynx and passes inferiorly to enter the thorax through the thoracic inlet
  • The thoracic oesophagus, the longest part, descends from the thoracic inlet to the diaphragm, which it pierces (through the oesophageal hiatus) to enter the abdominal cavity.
  • The abdominal oespohagus is a short segment (1.5 - 2 cm) that unites with the stomach at the gastro-oesophageal junction

There are several narrowings of the oesophagus which are related to sphincters or neighbouring structures

  • The junction of the oesophagus and laryngopharynx (15 cm from incisor teeth)
  • As the aortic arch passes anteriorly (22.5 cm from incisor teeth)
  • As the left main bronchus passes anteriorly (27.5 cm from incisor teeth)
  • At the gastro-oesophageal junction (40 cm from incisor teeth)

These provide important landmarks on gastroscopy.


The cervical oesophagus is related:

  • Anteriorly with the trachea
  • Anterolaterally with the thyroid gland and recurrent laryngeal nerves
  • Laterally with the common carotid artery, with the internal jugular vein beyond this
  • Posteriorly with the pre-vertebral muscles (longus colli) and the vertebral bodies of C6 and C7

The thoracic oesophagus has numerous relations:

  • Above the roots of the lungs:
    • Anteriorly with the trachea; the oesophagus is crossed by the left main bronchus, brachiocephalic artery and left brachiocephalic vein
    • Anterior and right with the brachiocephalic artery and right common carotid.
    • Anterior and left with the aortic arch and left common carotid
    • Laterally with the pleura and lungs; the azygos vein passes across its right lateral surface to reach the superior vena cava
    • Posteriorly with the thoracic vertebral bodies T1-T4
  • Below the roots of the lungs:
    • The heart lies anteriorly, separated by the pericardium
    • The azygos vein lies posteriorly, often separated by a segment of pleura and lung. The vertebral bodies of T5-T10 are also posterior.
    • The descending thoracic aorta is left lateral
    • The vagus nerves descend laterally before becoming the oesophageal plexus; they accompany the oesophagus through the oesophageal hiatus to reach the abdomen

The abdominal oesophagus has few relations:

  • The left lobe of the liver lies anteriorly and right lateral
  • The left diaphragmatic crus and left inferior phrenic artery lie posteriorly; separating the oesophagus from the vertebral body of T11
  • The stomach is left lateral

Microscopic Structure

The oesophagus has four histologically distinct layers:

  • The mucosa lines the lumen of the oesophagus.
    • The epithelium is normally stratified squmaous of non-keratinising type. Metaplastic change to simple columnar epithelium can be seen in the distal oesophagus
    • The lamina propria contains numerous vessels and nerves in connective tissue
    • The boundary between epithelium and lamina propria is uneven, with papillae of connective tissue serving as anchors for the overlying mucosa.
    • The muscularis mucosae is a narrow band of smooth muscle that forms the outer component of the mucosa. The fibres are usually arranged longitudinally, except at the gastro-oesophageal junction.
  • The submucosa lies between the mucosa and muscularis externa; it is an elastic tissue and contains oesophageal glands. These glands are tubuloacinar and are found in greatest density adjacent to the gastro-oesophageal junction
  • The muscularis externa consists of two thick layers (total width ≈ 300 μm); the inner layer is circular and the outer layer longitudinal
    • The muscle coat is interesting as it is comprised of striated muscle for the upper third; mixed striated and smooth for the middle third, and smooth muscle only for the lower third of the oesophagus
  • The adventitia is thin and formed by loose connective tissue. In the abdominal oesophagus there is an additional serosal layer of peritoneum in the adventitia.