The heart consists of different layers. The innermost layer is the endocardium. As the innermost layer, it comes into direct contact with the blood that flows through the heart. The endocardium (from inside to outside) contains the myocardium (the layer of the heart muscle) and the epicardium (the outer skin of the heart). The pericardium, the so-called pericardium, lies on the very outside and encloses the entire heart.
Structure/Histology
The endocardium is also divided into different layers. It is about 0.5 to 1.0 millimeters thick. From the inside out, the layers consist of the innermost layer, the endothelium.
The endothelium is a continuous, single-layered squamous epithelium that forms the smooth surface of the inner skin of the heart. It is covered by the subendothelial stratum, which consists of loose connective tissue in which elastic fibers are embedded. This is followed by the stratium myoelasticum, which consists of smooth muscles and collagen fibers.
Here are also some blood vessels and nerve fibers. The outermost layer of the endocardium is the Tela subendocardiale, which maintains the connection to the myocardium (heart muscle tissue). It also consists of loose connective tissue.
Function
The endocardium lines the entire heart, i.e. the ventricles as well as the papillary muscles and tendon threads from the inside. It also forms the four heart valves (aortic valve, pulmonary valve, mitral valve, tricuspid valve), which are in a sense duplicates of the endocardium. The heart valves are in turn suspended from the cardiac skeleton.
Since the endocardium has a very smooth surface, this promotes the regular and efficient flow of blood through the heart. The formation of thrombi (=concentration of blood platelets) is thus prevented. As soon as the surface of the endocardium shows small irregularities, which can be caused by endocarditis, for example, the risk of a thrombus is increased, which can trigger a heart attack.
Blood supply
The endocardium itself has hardly any blood vessels of its own, since it is supplied by the blood that flows through the heart. However, there is still a subendocardial capillary network that helps.
