part of part of pericardial cavity anatomical cavity mesocardium pericardial sinus http://upload.wikimedia.org/wikipedia/commons/7/7e/Gray489.png There are two Pericardial sinuses: transverse and oblique. The cul-de-sac enclosed between the limbs of the inverted U of the venous mesocardium lies behind the left atrium and is known as the oblique sinus. The passage between the venous and arterial mesocardiabi.e. , between the aorta and pulmonary artery in front and the superior vena cava behindbis termed the transverse sinus. Also, the sinus that forms in the pericardial cavity where the dorso-mesentary pericardium reside. Can be used to pass ligature during cardiac surgery. pericardial sinuses transverse pericardial transverse pericardial sinus oblique sinus oblique pericardial sinus Wikipedia:Pericardial_sinus oblique pericardial SCTID:314273005 UBERON:0010279