Changes in mucosal cross sectional area at gastroesophageal junction during swallowing. This graph shows the changes in the cross sectional area of the mucosa during swallowing in non-GERD subjects and in patients with GERD. The cross-sectional areas were measured by using endoluminal ultrasound placed in the gastroesophageal junction during swallowing. The x axis represents the time from the initiation of swallow, and the y axis represents the cross-sectional areas of the mucosa relative to baseline cross-sectional area at the beginning of swallow. The graph shows that there is less change in the cross-sectional area of the gastric mucosa in GERD patients when compared with non-GERD subjects.