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The esophagus (plural: esophagi or esophaguses) is a muscular tube that conveys food and fluids from the pharynx to the stomach. It forms part of the upper gastrointestinal tract.
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The esophagus 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 esophageal hiatus (T10) in the diaphragm which covers the inferior thoracic aperture
abdominal: from esophageal hiatus and is continuous with the cardia of the stomach at the gastro-esophageal junction
The cervical esophagus begins at the upper esophageal sphincter, which is formed by the cricopharyngeus muscle 6.
The esophagus 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 esophagus then curves anteriorly to pass through the diaphragm into the abdominal cavity.
The lower esophageal sphincter, a specialized region of the circular muscle of the distal esophagus, manifests itself radiographically as the phrenic ampulla (a.k.a. esophageal vestibule), a 2-4 cm long dilatation between the A-ring and B-ring 6.
There are three normal esophageal 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 esophageal hiatus at the level of T10/11
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-esophageal groove); left main bronchus; left atrium
left lateral: lung; pleura; aorta; left subclavian artery; thoracic duct
right lateral: lung; pleura; azygos vein
upper third: inferior thyroid artery
middle third: esophageal branches of the thoracic aorta and by the bronchial arteries
lower third: esophageal branches of the left gastric artery
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)
Follows arterial supply:
upper third: deep cervical lymph nodes
middle third: posterior mediastinal lymph nodes
lower third: left gastric and celiac group lymph nodes
However it is important to note that within the esophageal walls, there are lymphatic channels which enable lymph to pass for long distances. Therefore, drainage may not necessarily follow any strict pattern.
The esophagus is made up of five layers, noting there is no serosal layer. From outer to inner, these are:
outer longitudinal muscularis propria
inner circular muscularis propria (in the upper one-third of the esophagus this layer is composed of striated (voluntary) muscle while the lower two-thirds is smooth muscle)
stratified squamous epithelium that abruptly changes to columnar epithelium in the lower esophagus
Majority of the anatomical variations of the esophagus are congenital, typically occurring at time of separation from the trachea (around third to seventh weeks intrauterine)
esophageal diverticulum (congenital variant is typically rare)
aberrant right subclavian artery passing anterior or posterior to the esophagus
modified barium swallow is used to evaluate pharyngeal motility during swallowing; the procedure utilizes barium of varying consistencies given by mouth with video recording of swallowing
barium swallow is the main radiological method of assessing the esophagus; double contrast esophagogram using CO2 gas-forming crystals and barium contrast are used to distend the esophagus and coat the mucosa
Endoscopic ultrasonography is used for evaluation of the depth of the esophageal tumor.
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
T1: isointense to muscle
T2: hyperintense to muscle
Useful for the staging of esophageal cancer.
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