Pericardial sinus

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 mesocardia—i.e., between the aorta and pulmonary artery in front and the atria behind—is termed the transverse sinus.