muscle that can be identified histologically, and it does
at times permit the acidic contents of the stomach to
enter the esophagus. This can create a burning sensation
commonly called heartburn, although the heart is not involved.
In infants under a year of age, the lower esophageal
sphincter may function erratically, causing them to “spit up” following meals .
Certain mammals, such as rodents, have a true gastroesophageal
sphincter and thus cannot regurgitate. This is why
poison grains are effective in killing mice and rats.