The complaints of dysphagia, odynophagia, and ingested foreign body immediately implicate the esophagus. The esophagus also is often the site of pathology in patients who present with chest pain, upper GI bleeding (see chapter 75, "Upper Gastrointestinal Bleeding"), malignancy, and mediastinitis. Many diseases of the esophagus can be evaluated over time in an outpatient setting, but several, such as esophageal foreign body and esophageal perforation, require emergent intervention.
ANATOMY AND PATHOPHYSIOLOGY
The esophagus is a muscular tube approximately 20 to 25 cm long, primarily located in the mediastinum, posterior and slightly lateral to the trachea, with smaller cervical and abdominal components, as shown in Figure 77–1. There is an outer longitudinal muscle layer and an inner circular muscle layer. The upper third of the esophagus is striated muscle, while the lower half is all smooth muscle (including the lower esophageal sphincter). The esophagus is lined with stratified squamous epithelial cells that have no secretory function.
Anatomic relations of the esophagus (seen from the left side). The distance from the upper incisor teeth to the beginning of the esophagus (cricoid cartilage) is about 15 cm (6 in); from the upper incisors to the level of the bronchi, 22 to 23 cm (9 in); and to the cardia, 40 cm (16 in). Structures contiguous to the esophagus that affect esophageal function are shown.
Two sphincters regulate the passage of material into and out of the esophagus. The upper esophageal sphincter prevents air from entering the esophagus and food from refluxing into the pharynx. The lower esophageal sphincter regulates the passage of food into the stomach and prevents stomach contents from refluxing into the esophagus. The upper sphincter is composed primarily of the cricopharyngeus muscle, with a resting pressure of around 100 mm Hg. The lower sphincter is not anatomically discrete. The smooth muscle of the lower 1 to 2 cm of the esophagus, in combination with the skeletal muscle of the diaphragmatic hiatus, functions as the sphincter, with a lower resting pressure around 25 mm Hg. An empty esophagus collapses, but three anatomic constrictions affect the adult esophagus:
At the cricopharyngeus muscle (C6)
At the level of the aortic arch (T4)
At the gastroesophageal junction (T10 to T11)
The pediatric esophagus gets two additional areas of constriction:
At the thoracic inlet (T1)
At the tracheal bifurcation (T6)
The innervation of the heart mirrors that of the esophagus, with visceral and somatic stimuli converging within the sympathetic system. This anatomy makes pain of esophageal and cardiac origin similar. The esophageal venous circulation includes a submucosal plexus of veins that drains into a separate plexus of veins surrounding the esophagus. Blood flows from this outer plexus in part to the gastric venous system, an ...