The esophagus is the muscular tube that carries food and water from the mouth to the stomach, running a course of roughly 125 to 150 centimeters in the adult horse — longer than in most domestic species — descending through the neck along the left side of the trachea before passing through the thorax and entering the stomach at the cardiac sphincter.
Its equine significance is defined by two anatomical facts that shape clinical reality. First, the horse cannot vomit. The cardiac sphincter is so powerful, and the stomach wall so resistant to distension, that retrograde movement of ingesta is mechanically blocked under almost all conditions; material entering the stomach stays there, which is why gastric rupture is a catastrophic and rapidly fatal event when impaction or gas accumulation overwhelms the organ. Second, the esophageal wall in the horse contains striated muscle along most of its length — unlike the smooth-muscle-dominant esophagus of many other species — giving it relatively strong peristaltic force, yet that same structure makes it vulnerable to injury when a bolus is forced against an obstruction.
The defining clinical condition of the equine esophagus is choke: esophageal obstruction. Choke occurs when poorly chewed feed — dried beet pulp, large pieces of carrot, unchewed hay — lodges in the esophagus, most commonly at the thoracic inlet or at the base of the neck. The horse shows nasal discharge of feed material and saliva, repeated swallowing attempts, neck extension, and distress. Unlike gastric colic, choke is rarely immediately life-threatening, but prolonged obstruction risks aspiration pneumonia from material overflowing the nares, and pressure necrosis of the esophageal wall. Treatment is nasogastric intubation with gentle lavage; severe or recurrent cases may indicate stricture, a narrowed segment of healed scar tissue that predisposes the horse to repeat obstruction and may require endoscopic or surgical management.
Because the esophagus is left-sided in its cervical course, a large bolus obstruction is sometimes palpable or visible as a firm swelling low on the left side of the neck — a clinical sign unique to the species and a reliable field indicator before diagnostics are available.