The esophagus is a dynamic tube that transports saliva, liquids, and solids from the mouth to the stomach. It accomplishes this task through the action of skeletal and smooth muscles that create waves of contraction known as peristalsis, which push food toward the anus and facilitate swallowing. In the esophagus, the mucosa provides lubrication to facilitate passage of these substances. The esophagus also secretes mucus that assists in digestion and absorption.
In embryology, the esophagus forms from primitive foregut endoderm during weeks 4 to 6 of gestation. By week 12, the esophagus begins to lengthen. At this time, the original cell lining of the embryonic esophagus transforms from a pseudostratified columnar epithelium to a stratified squamous epithelium. Residual islands of ciliated epithelium remain in the proximal and distal ends of the embryonic esophagus and give rise to esophageal glands.
When the esophagus is fully mature, it is segmentally vascularized with cranial arteries from the branchial arches and caudal ones from branches of the aorta. Its venous supply is segmental as well, with the proximal part draining into the azygos and hemiazygos veins and the distal part descending to the left gastric and short gastric veins.
As the esophagus courses through the thoracic cavity, it is anchored superiorly to the cricoid cartilage and pharynx by strips of collagen fibers interspersed with muscle fibers. It is tethered to the left and right pulmonary lobes by a strip of fibrous connective tissue, the pericardium, and the thoracic diaphragm by a strip of connective tissue containing muscle fibers. The esophagus is also tethered to the trachea by the esophageal fistula, a communication between the respiratory and digestive tracts that occurs in some premature infants with tracheoesophageal atresia.
The esophagus receives dual sensory innervation via the parasympathetic and sympathetic nerves, which are supplied by the recurrent laryngeal and cervical sympathetic trunks. The esophagus does not have conscious control; instead, it is under involuntary control by the autonomic nervous system.
Depending on the diagnosis, an esophageal stricture can be benign or malignant. Benign strictures are more likely to be caused by chronic dysphagia, while malignant strictures are more likely to be due to neoplasms or inflammatory diseases that involve the muscularis mucosa. A benign stricture is characterized by concentric narrowing of the lumen with associated nodularity, whereas a malignant one is often accompanied by difficulty swallowing.
When measured by water perfusion manometry, the esophageal pressure–time curve (dP/dt) is steeper in the proximal than distal esophagus. However, the difference in dP/dt is less when the esophageal lumen is distended by a bolus of liquid or a meal.
An abnormal esophageal pressure–time profile is a typical finding in patients with diffuse esophageal spasm (DES). It is important to note that, as a result of DES, the esophageal lumen expands as a bolus enters the distal esophagus, and the dP/dt decreases. Consequently, the esophageal pressure–time relationship may be normal during resting conditions but is markedly abnormal when the patient swallows.
