The esophagus is a muscular tube about 25 cm long that runs behind the trachea and the heart. It carries food and liquid from the pharynx to the stomach.
Structure
The upper third has skeletal muscle and the lower part has smooth muscle. It passes through the diaphragm at the esophageal hiatus to join the stomach.
Peristalsis
Coordinated waves of muscle contraction push the bolus down, so swallowing works even when lying flat. A swallow reaches the stomach in about 5 to 10 seconds.
Two sphincters
The upper esophageal sphincter keeps air out of the esophagus during breathing. The lower esophageal sphincter relaxes to let food in, then closes to keep stomach acid from coming back up.
The lining
The esophagus is lined with stratified squamous epithelium, which resists wear but not acid. Repeated reflux inflames it and, over years, can change the lining (Barrett's esophagus).
At the bedside
Heartburn suggests a weak lower sphincter, and food sticking suggests a narrowing or a motility problem. The distance from nose to earlobe to xiphoid process guides the length of a nasogastric tube.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).