fibrous skeleton of heart

fi·brous skel·e·ton of heart

a complex framework of dense collagen forming four fibrous rings (anuli fibrosi), which surround the ostia of the valves, a right and left fibrous trigone, formed by connecting the rings, and the membranous portions of the interatrial and interventricular septa; it is found in association with the base of the ventricles, that is, at the level of the coronary sulcus; its functions include: contributing reinforcement of the valvular ostia while providing attachment for the leaflets and cusps of the valves; providing origin and insertion for the myocardium; and serving as a sort of electrical "insulator," separating the electrically conducted impulses of the atria and ventricles and providing passage for the common atrioventricular bundle of conductive tissue through the right fibrous trigone and membranous interventricular septum.