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.
The right and left lung are not symmetrical, since your right lung has three lobes and your left lung has two. The lobes on both sides of your lungs are separated by fissures. The oblique fissure separates the largest lobe, the left upper lobe, or superior lobe, from the one below it. The lower is called the left lower, or inferior, lobe.