The endothelium is a single-layered, non-cornifying squamous epithelium that lines the heart, blood and lymph vessels and acts as a selective barrier between the blood stream and the vessel wall for dissolved substances, macromolecules and cells. The endothelium actively controls the exchange between vascular lumen and interstitium. The endothelium has a superior function in the formation of thrombi.
The release of thrombogenic factors leads to the formation of a thrombus, initially consisting mainly of thrombocytes.
The endothelial factors that cause a thrombotic effect are:
Factor III (also called tissue factor or thromboplastin), an important activator of plasmatic coagulation from the subendothelium
The factor V
The platelet activator factor (PAF)
The "high-molecular-weight-kininogen" (HMWK), also called factor XIV or Fitzgerald factor
The collagen
The plasminogen activator inhibitor-1 (PAI-1) = inhibitor of fribrinolysis.
The endothelium expresses receptors for:
Tenase
Prothrombinase
Via these receptors, the corresponding factors bind to the endothelium at the site of the lesion. The endothelium also binds fibrinogen, fibronectin and thrombin.