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The heart’s apex lies at the fifth left intercostal space near the midclavicular line, while its base faces posteriorly. Fibrous and serous pericardial layers enclose it; the heart wall consists of endocardium, myocardium, and epicardium. Four chambers are separated by septa, and atrioventricular and semilunar valves direct blood through the heart. The cardiac skeleton supports valve attachment and electrically separates atria from ventricles. Coronary arteries supply the heart, with dominance defined by which artery gives rise to the posterior descending artery. Venous blood returns mainly through the coronary sinus. The intrinsic conduction pathway runs from the sinoatrial node through the atrioventricular node and His–Purkinje system, while autonomic input influences heart rate and contractility.