Cardiac histology defines the heart wall as three concentric layers—epicardium, myocardium, and endocardium (the latter lined by endothelium)—with the myocardium composed of striated, branched, mononucleated cardiac muscle fibers joined end-to-end by intercalated discs. These discs contain adherent junctions for mechanical coupling and gap junctions that permit ion/signal passage between cells, enabling coordinated contraction. The conduction system, distinct from contractile cardiac muscle, originates impulses at the sinoatrial node and propagates them via specialized, non-contractile Purkinje fibers to the ventricular myocardium.
Cardiac histology defines the heart wall as three concentric layers—epicardium, myocardium, and endocardium (the latter lined by endothelium)—with the myocardium composed of striated, branched, monon…