| 1 | Some people are born with a naturally weak sphincter (LES). | |
| 2 | If the sphincter does not work properly, stomach acid flows into the oesophagus. | |
| 3 | It is conversely true that Leonardo drew many highly detailed studies of the anal sphincter. | |
| 4 | When you' re comfortable enough to begin probing, you should keep things slow and gentle, taking care to relax your sphincter during the process. | |
| 5 | At the lower end of the esophagus is a small ring of muscle called the lower esophageal sphincter (LES). |