Which of the following statements about esophageal anatomy is correct?

C. The esophagus has two distinct muscle layers, an outer, longitudinal one and an inner, circular one, which are striated in the upper third and smooth in the distal two thirds.

DISCUSSION: Poor technique, not poor blood supply, explains most esophageal anastomotic leaks. While the major blood supply of the esophagus is from four to six segmental aortic esophageal arteries, there are extensive submucosal collaterals from the inferior thyroid, intercostal, bronchial, inferior phrenic, and left gastric arteries. The esophagus lacks serosa and instead is surrounded by mediastinal connective tissue (adventitia). There are two muscle layers in the esophagus, an outer longitudinal and an inner circular one. Both layers of the upper third of the esophagus consist of striated muscle, while in the lower two thirds they are (nonstriated) smooth muscle. The recurrent laryngeal branches of the vagus nerves provide both parasympathetic innervation to the cervical esophagus and innervation to the upper esophageal sphincter (UES). Injury to the recurrent laryngeal nerve therefore results in improved UES function with secondary aspiration on swallowing as well as vocal cord dysfunction and hoarseness. The esophagus has extensive lymphatic drainage, with lymphatic capillaries coursing longitudinally in the esophageal wall and communicating with paraesophageal, paratracheal and subcarinal, other mediastinal, perigastric, and internal jugular lymph nodes. This accounts for the biologically aggressive nature of esophageal carcinoma, which tends to metastasize early in its course.