Endothelial thrombotic functions

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:

• The von Willebrand factor

• 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:

• factor XIV

• Tenase

• Prothrombinase

• Factor IX

• factor X

• von Willebrand factor

• Fibrinogen

Via these receptors, the corresponding factors bind to the endothelium at the site of the lesion. The endothelium also binds fibrinogen, fibronectin and thrombin.