The vascular supply of the heart includes a variety of vessel types. The coronary arteries give rise to arteries which penetrate the wall, branch to supply the epicardium, myocardium, and endocardium, and may empty into the cardiac chambers. Valve leaflets are composed of three layers. The fibrosa is dense collagen that extends up from the valve ring to the free edges, and in the case of the atrioventricular valves, into the chordae tendineae. It serves as the shock absorber.
All layers contain some fibroblasts.
There are nerves and lymphatics, but no blood vessels, in the leaflets. The chordae tendineae are tough fibrous bands, with cores composed sometimes of cardiac muscle, sometimes of fibrous tissue. The outside extends into the fibrous cap on the tips of the papillary muscles. The conduction system is myocardial fibers designed for rhythm rather than contraction. You can spot the sinoatrial node where the superior vena cave joins the crest of the right atrial appendage, just under where the fibrous pericardium takes off.