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.
There isn't a valve between the right atrium and left ventricle. The valve between the right atrium and right ventricle is the tricuspid valve; the valve between the left atrium and left ventricle is the mitral valve. If your right atrium is connected to your left ventricle, you have a condition known as AVSD (atrioventricular septal defect). There isn't a valve between the right atrium and left ventricle.