The normal oesophagus measures around 25 cm in length, commencing at the cricopharyngeus (inferior constrictor of the pharynx) at the level of the sixth cervical vertebra (C6). It ends at the gastro-oesophageal junction where it joins the cardia of the stomach at the level of the eleventh thoracic vertebra (T11). The gastro-oesophageal junction is normally found at 40 cm from the incisors on an oesophago-gastroduodenoscopy (OGD).
- Cervical oesophagus: the trachea is anterior, vertebral bodies posterior, thyroid and common carotids laterally
- Thoracic oesophagus: superiorly, trachea anterior and vertebral bodies posterior. In the mediastinum, it passes behind and to the right of the aortic arch (AA). Descending, it has the aorta to its left, the right pleura and azygos vein to its right, and passes behind the left main bronchus and left atrium. It passes through the diaphragm at T10, anterior to the aortic hiatus
- Abdominal oesophagus: a fibrous cuff (Laimer’s fascia) surrounds the oesophagus and provides a seal between thorax/abdomen. Left lobe of liver anteriorly
The normal oesophageal mucosa consists of squamous epithelium, with transition to columnar epithelium at the gastro-oesophageal junction. The transition is not straight but somewhat irregular and is known as the Z-line. Below this layer lies the muscularis mucosa, and beneath that is the submucosa. Within the connective tissue of this layer lie mucous glands, vessels and nerves.
Below the submucosa is the muscle layer of the wall – this consists of an outer layer with longitudinal fibres and an inner circular layer. There is a transition from striated (upper third) to smooth muscle (lower third). The external/adventitial layer is the outermost layer of the wall. These five layers can be seen on endoscopic ultrasound (EUS).
The barium swallow can demonstrate mucosal surface and lumen only, although intramural and extramural pathologies can be inferred where the mucosal surface is indented.