The lines of reflection between visceral and parietal pericardium form two pericardial sinuses, the transverse pericardial sinus and the oblique pericardial sinus. The transverse pericardial sinus lies anterior to the superior vena cava and posterior to the ascending aorta and pulmonary trunk. Place your finger in the transverse pericardial sinus and examine the relationships of the structures.
The oblique pericardial sinus lies posterior to the heart in the pericardial sac. Lift the apex of the heart and place your fingers posterior to the heart to identify the oblique pericardial sinus and examine its borders. On the right side, the oblique sinus is bounded by the lines of reflection of the serous pericardium onto the inferior vena cava and the right pulmonary veins. On the left, the sinus is bounded only by the lines of reflection of serous pericardium onto the left pulmonary veins. Observe that the two sinuses are not continuous with one another.
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