esophagus
Meaning of esophagus: A valve at each end keeps traffic moving one way, and it is failure of the lower one that causes most trouble.
Definition of esophagus
The esophagus is the muscular tube that carries swallowed food and liquid from the throat to the stomach. Roughly the length of a forearm, it runs behind the windpipe, down through the chest, and passes through an opening in the diaphragm to reach the stomach just below. It performs no digestion of its own.
How does it move food?
Swallowing begins voluntarily, then hands over. The upper portion of the wall is made of striated muscle, the same kind found in a limb, while further down it becomes smooth muscle beyond conscious control. Once a mouthful passes the throat, a coordinated wave of contraction called peristalsis travels the length of the tube, tightening behind the material and relaxing ahead of it. The wave is strong enough to work against gravity, which is why swallowing succeeds while lying flat or upside down. If some residue remains behind, stretching of the wall triggers a second wave to clear it.
What keeps stomach contents from coming back up?
| Upper sphincter | Lower sphincter | |
|---|---|---|
| Position | Where the throat meets the tube | Where the tube meets the stomach |
| Muscle type | Striated | Smooth, reinforced by the diaphragm around it |
| Job | Keeps swallowed air out and protects the airway | Opens for a swallow, otherwise stays shut |
The lower ring is not a true valve but a zone of sustained tension, helped by the muscular pinch of the diaphragm at the same level. When a portion of the stomach slides up through that opening, the two components separate and the barrier weakens. Acid then reaches a lining with none of the stomach's protection, producing the burning of acid reflux.
What goes wrong with it?
Repeated acid exposure inflames the lining and, over years, can replace it with a different cell type better able to withstand acid, a change known as Barrett esophagus that is followed because it carries an increased cancer risk. Scarring from the same process narrows the tube and makes solid food stick. Coordination can fail instead, leaving the lower ring unable to relax so that food collects above it. In advanced liver disease, veins in the wall swell under back pressure and can bleed heavily. Endoscopy, passing a flexible camera down the tube, is the standard way to look at the lining directly.
Also known as
Used in a sentence
Endoscopy was performed to examine the lining of the esophagus for evidence of inflammation.
Good to know
Backward movement of stomach acid into the esophagus happens when the lower sphincter and the diaphragm around it fail to hold, a mechanism distinct from inflammation caused by an infection or a swallowed irritant.
Word origin
Where “esophagus” comes from
From Greek oisophagos, a term formed from a root related to carrying and phagein, meaning to eat, together describing the passage that carries what is eaten toward the stomach.