The word "sphincter" refers to a circular muscle that acts like a gate or valve in our body. It helps control the opening and closing of certain body parts, like the ones in our digestive system or the muscles around our eyes. Full definition
The stomach acids and food that keeps coming up are often due to the underdeveloped lower esophageal sphincter muscle between the stomach and the esophagus. (myorganicformula.com)
In babies who have reflux, the lower esophageal sphincter muscle is not fully developed and lets the stomach contents back up the esophagus. (medlineplus.gov)
Ashwini Mudra is done by contracting the anal sphincter muscles in a rhythmic manner. (yogicwayoflife.com)