The course of the esophagus is shown from the right. The blood supply to the upper esophagus is from the inferior thyroid artery, to the mid-esophagus from bronchial and aortic branches, and to the lower esophagus from phrenic and left gastric branches. The lack of serosa on the esophagus predisposes to lymphatic spread, and explains why most esophageal lesions are already advanced when detected. The lack of serosa also makes esophageal anastomoses more tenuous. The rich submucosal plexus of vessels and lymphatics predisposes to longitudinal spread. The esophagus is covered by the mediastinal portion of the parietal pleura.