Gerinnungssystem/en

Hemostasis; the ability of the blood to close a wound.

The blood taken from the blood vessels "coagulates" spontaneously in the test tube within a few minutes. The blood changes from a liquid state to a gelatinous state with the participation of formed elements. The property of blood to coagulate outside the vascular system is an extremely vital process whose importance lies in protecting the body from loss of its blood fluid.

The wound plug, initially composed solely of thrombocytes, is not capable of permanently closing the injured vascular site. This is also a good thing, because otherwise such grafts could sometimes be formed too quickly. The complex coagulation system ensures that coagulation only takes place when it is really needed.

It is activated at the site of the injury at the same time as the complex platelet processes take place. Its clearly slower process ends in the formation of fibrin threads, which spin through the wound graft in a net-like manner and usually also deposit in the immediate vicinity of the graft, whereby abundant erythrocytes are included.

The final strength of the closure plug is achieved by the contraction of the platelets, which are "felted" with their pseudopodia and fibrin threads.

This process, which normally takes 5 - 7 minutes (coagulation time), involves platelets as well as a large number of plasmatic factors.

The actual coagulation process - like primary haemostasis - is triggered by the vessel and tissue injury and activated in two different ways: *exogenous or extravascular way (Extrinsic System) *endogenous or intravascular way (Intrinsic System)

Auf dem exogenen Weg erfolgt die Aktivierung sehr schnell (innerhalb von Sekunden), während der Aktivierungsprozess auf dem endogenen Weg über eine größere Zahl von Zwischenstufen abläuft und längere Zeit (Minuten) benötigt. An dem normalen Gerinnungsablauf sind in der Regel beide Systeme ineinandergreifend beteiligt. Durch die gemeinsame Endstufe der beiden aktivierenden Systeme wird schließlich Prothrombin (Faktor II) und unter Mitwirkung von Vitamin K das in der Leber gebildet wird, in Thrombin umgewandelt. Das so entstandene Thrombin ist ein Enzym, welches das gleichfalls in der Leber synthetisierte Fibrinogen (Faktor I) spaltet und damit die Bildung von Fibrin einleitet.

https://de.wikipedia.org/wiki/Hämostase _{(Wikipedia CC-by-sa-3.0)}