It is a closed sac having two layers: the visceral layer (epicardium), immediately surrounding the heart, and the outer parietal layer, forming the sac, composed of strong fibrous tissue, the fibrous pericardium, lined with a serous membrane, the serous pericardium. Synonym(s): heart sac, theca cordis.
The right and left cavernous sinuses are interconnected by the anterior and posterior intercavernous sinuses. Tributaries of the cavernous sinus include the superior ophthalmic, superficial middle cerebral, and inferior cerebral veins and the sphenoparietal sinus.
blood from the body enters the right atrium via the superior vena cava (upper body) and inferior vena cava (lower body). A coronary sinus also drains into the right atrium bringing blood from the heart itself. The right atrium squeezes blood through the atrioventricular (AV) opening into the muscular right ventricle.