The only secretion of the esophagus is mucus, for lubrication. The esophagus does not secrete any digestive chemicals because its role is to deliver boluses of food from the pharynx to the stomach.
The mucus is produced by mucous glands located in the mucosa, the lining of the esophagus. This lining is composed of stratified squamous epithelium, which is resistant to trauma from abrasive foods. During swallowing, boluses of food distend the esophagus, causing mucus to be expressed from the mucous glands. Peristaltic contractions then propel the food into the stomach. In humans, it takes four to five seconds for a bolus of food to go through the esophagus.