endokardu

Endokard is the innermost lining of the heart, covering the interior surfaces of all four chambers and the heart valves. It is continuous with the endothelium of the great vessels and forms a smooth, non-thrombogenic surface that reduces turbulence as blood flows through the heart.

Anatomically, the endocardium consists mainly of endothelial cells supported by a thin subendothelial connective tissue. In the ventricular regions, the subendocardial layer contains specialized Purkinje fibers that are part of the cardiac conduction system. The thickness and specific composition of the endocardium vary by chamber and location.

The primary function of the endocardium is to provide a smooth interface between blood and the heart tissue, minimizing friction and protecting the underlying myocardium. It also acts as a barrier between circulating blood and the myocardium and participates in the regulation of local electrical conduction through its subendocardial components. The endocardium is best protected when the myocardium receives adequate blood flow, but it is prone to ischemic injury in conditions of reduced coronary perfusion.

Clinically, inflammation of the endocardium is known as endocarditis, typically affecting the heart valves and often caused by bacterial or fungal infections. Endocarditis can lead to valvular damage, regurgitation, and heart failure. Non-infective forms, such as nonbacterial thrombotic endocarditis, can occur in states of hypercoagulability. Embryologically, the endocardium originates from the heart tube endothelium, with endocardial cushions contributing to the formation of valves and portions of the septa.

Relation to other heart layers: the endocardium lies between the myocardium and the heart lumen, distinct from the outer epicardium (visceral pericardium) and the muscular myocardium.