part of part of adjacent to adjacent to heart cardiac atrium cardiac ventricle thoracic segment connective tissue cardiac skeleton http://upload.wikimedia.org/wikipedia/commons/5/50/Gray495.png trigonum fibrosum dextrum cordis EMAPA:36645 trigonum fibrosum sinistrum cordis Dense connective tissue that separates the atria from the ventricles and provides physical support for the heart. It is not a true skeleton, but it does provide structure and support for the heart, as well as isolating the atria from the ventricles. This allows the AV node and AV bundle to delay the wave of depolarisation such that the atria can contract and assist in ventricular filling before the ventricles themselves depolarise and contract (the AV bundle is the only part of the conduction system that passes from the atria to the ventricles in a normal heart). It also allows the valves (bicuspid, tricuspid, semilunar) to keep open by giving them structural support[WP] cardiac fibrous skeleton anulus fibrosus dexter cordis heart fibrous skeleton skeleton of heart trigona fibrosa Wikipedia:Cardiac_skeleton FMA:9496 anulus fibrosus sinister cordis fibrous skeleton of heart UBERON:0004292