subsequently the nature of the serosa tissue is used to advantage for its ability to bond to like serosa tissue the fundus 46 of the greater curvature 44 forms the superior portion of the stomach 43 and traps gas and air bubbles for burping the esophageal tract 41 enters the stomach 43 at an esophageal orifice below the superior portion of the fundus 46 forming a cardiac notch 47 and an acute angle with respect to the fundus 46 known as the angle of his 57 the lower esophageal sphincter les 48 is a discriminating sphincter able to distinguish between burping gas liquids and solids and works in conjunction with the fundus 46 to burp the gastroesophageal flap valve gefv 49 includes a moveable portion and an opposing more stationary portion the moveable portion of the gefv 49 is an approximately 180 degree semicircular gastroesophageal flap 50 alternatively referred to as a u201c normal moveable flap u201d or u201c moveable flap u201d formed of tissue at the intersection between the esophagus 41 and the stomach 43 the opposing more stationary portion of the gefv 49 comprises a portion of the lesser curvature 45 of the stomach 43 adjacent to its junction with the esophagus 41 the gastroesophageal flap 50 of the gefv 49 principally comprises tissue adjacent to the fundus 46 portion of the stomach 43 it is about 4 to 5 cm long 51 at it longest portion and its length may taper at its anterior and posterior ends the gastroesophageal flap 50 is partially held against the lesser curvature 45 portion of the stomach 43 by the pressure differential between the stomach 43 and.