the stomach or esophagus is often referred to as simple achalasia. the lower esophageal sphincter does not relax, causing

achalasia acid anatomy animal background body causing diaphragm digestive disease does drawing endotracheal engraving esophageal esophagus expansion fundus gastric gastroenterology gastroesophageal health heartburn hernia herniation illness illustration indigestion inflammation intervention isolated junction larynx lower medical medicine not often organ paraesophageal pylorus referred reflux relax rings science simple sliding sphincter stomach swallowing system throat trachea tracheal tube type valve