Anatomy of the Heart Epicardium: thin outer connective layer where coronary vessels travel through (Fat) Endocardium: thin connective layer that lines the interior of the heart (no fat) Myocardium: thick middle muscle layer that performs the work of the heart Fibrous skeleton: support and anchor

Chambers R atria: thin myocardium, receives blood from the three great veins L atria: thin myocardium, receives blood from pulmonary veins R ventricle: thicker myocardium, receives from tricuspid, pushes to pulmonary arteries L ventricle: thickest myocardium, receives from bicuspid, pushes to rest of body Chambers divided by septum's

Valves Valves ensure one-way flow Each valve is made of two to three fibrous flaps called cusps Chordae tendineae: fibrous strings that attach to cusps and papillary muscles of ventricles to reduce bulging Semilunar valves: each has three flaps regulated by pressure differences