The lower esophageal sphincter (LES) and crural diaphragm (CD) provide the closure mechanism at esophago-gastric junction (EGJ). We used CT imaging in combination with 3D EGJ pressure recordings to determine the functional morphology of the LES and CD and its relationship to the EGJ anatomy. A 3D-HRM catheter recorded the EGJ pressure in 10 healthy subjects. A 0.5 mm diameter metal ball (BB) was taped to the catheter, adjacent to transducer #1. The EGJ pressure was recorded under following conditions; 1) end-expiration (LES pressure) a) before swallow, b) after swallow, and 2) peak inspiration (CD contraction) c) tidal inspiration and d) forced inspiration. A CT scan was performed to localize the circumferential orientation of the BB. The LES pressure varied under different conditions but the shape of pressure profile was not different with the LES length longer towards the lesser as compared to greater curvature of stomach. The LES pressure profile revealed circular pressure asymmetry, with greatest pressure and shortest cranio-caudal length on the left. The CD contraction with inspiration increased pressure in the cranial half of the LES pressure profile and it was placed horizontally. The CT images revealed that the hiatus is placed obliquely across the esophagus, however, due to the bend of the esophagus to the left the two are placed at right angle to each other. Our observations suggest a unique shape of the LOS, CD and the anatomical relationship between the two, which provides explanation as to why the LOS pressure is circumferentially asymmetric.