The esophagus is a muscular tube that serves as a conduit for the passage of food and fluids from the pharynx to the stomach. It originates at the level of the sixth cervical vertebra, posterior to the cricoid cartilage. In the thorax, the esophagus passes behind the aortic arch and the left main stem bronchus, enters the abdomen through the esophageal hiatus of the diaphragm, and terminates in the fundus of the stomach. Its muscle fibers originate from the cricoid cartilage and pharynx above and interdigitate with those of the stomach below. About 2-4 cm of esophagus is normally located below the diaphragm. The junction between the esophagus and stomach is maintained in its normal intra-abdominal position by the reflection of the peritoneum onto the stomach and of the phrenoesophageal ligament onto the esophagus. The latter is a fibroelastic membrane that lies beneath the peritoneum, on the inferior surface of the diaphragm. When it reaches the esophageal hiatus, the ligament is reflected in an orad direction onto the lower esophagus, where it inserts into the circular muscle layer above the gastroesophageal sphincter, 2-4 cm above the diaphragm (Figure 22–1).
Anatomy of the esophagus.
Three anatomic areas of narrowing occur in the esophagus: (1) at the level of the cricoid cartilage (pharyngoesophageal or upper esophageal sphincter); (2) in the mid thorax, from compression by the aortic arch and the left main stem bronchus; and (3) at the level of the esophageal hiatus of the diaphragm (gastroesophageal or lower esophageal sphincter).
In the adult, the distance as measured from the upper incisor teeth to the cricopharyngeus muscle is 15-20 cm; to the aortic arch, 20-25 cm; to the inferior pulmonary vein, 30-35 cm; and to the gastroesophageal junction, approximately 40-45 cm.
The mucosal lining of the esophagus consists of stratified squamous epithelium that contains scattered mucous glands throughout. The musculature of the pharynx and upper third of the esophagus is skeletal in type (striated muscle); the remainder is smooth muscle. Physiologically, the entire organ behaves as a single functioning unit, so that no distinction can be made between the upper and lower esophagus from the standpoint of propulsive activity. As in the intestinal tract, the muscle fibers are arranged into inner circular and outer longitudinal layers. The esophagus has no serosal layer.
The arterial supply to the esophagus is quite consistent. The upper end is supplied by branches from the inferior thyroid arteries. The thoracic portion receives blood from the bronchial arteries and from esophageal branches originating directly from the aorta. The intercostal arteries may also contribute. The diaphragmatic and abdominal segments are nourished by the left inferior phrenic artery and by the esophageal branches of the left gastric artery. The venous drainage is more ...