Thrombosis Flashcards
What is a clotting factor?
A group of proteins in the blood
many are produced by the liver or endothelial cells
What does factor xa convert prothrombin into?
thrombin
what does thrombin then convert fibrinogen into?
fibrin
it’s insoluble - a blood clot
define thrombus?
it is a blood clot that occurs within a vein
what is a blood clot?
just a coagulation of blood but generally all around the body
structure of a typical vein
interstitial collagen fibers surrounding outside
then smooth muscle lining of lumen
then basal lamina (basement membrane)
inside lumen you have plasma which has WBCs, RBCs, and platelets
plasma also contains clotting factors- without these it would be called serum
what are the 2 path ways in blood clotting
intrinsic (damaged surface)
extrinsic (trauma- extreme)
these converge to form the common pathway
what is the clotting cascade?
an amplification system
what could initial damage to a blood vessel be cause by?
trauma- leads to exposure of interstitial collagens or of a molecule called tissue factor
what is a tissue factor?
a molecule present on muscle cells and is released by it- once released it can bind a clotting factor and initiate the clotting cascade
what are serine proteases?
they have a serine amino acid in them and they cleave other clotting factors to activate them and then they go on to do the same
many clotting factors are serine proteases
what does the clotting cascade lead to the production of? and what is the end point?
thrombin
the end point is the production of insoluble fibrin strands that form a meshwork
Platelets
what are they?
how do they work?
formed in the bone marrow
they form a cell called megakaryocyte with many nuclei (undergoes nuclear division but not cell division)
platelets bud off as fragments from cytoplasmic extension
they work by trying to close the gap caused by trauma to a vessel which happens when they’re exposed to interstitial collagen
what are the 2 types of coagulation?
thrombus formation
blood clot formation
thrombus formation (thrombosis)
it occurs in flowing blood as platelets have molecules on their surface which allow adherence to interstitial collagen even when blood is flowing past them
pure thrombus= pale cream colour
it consists of platelets and a mesh like network of fibrin strands
clot formation
blood leaks out of a vessel and becomes stationary (or stagnant)
within the stagnant blood, sitting next to the interstitial collagen, the clotting cascade is activated
what does a clot consist of
a network of fibrin strands and RBC’s
define haemostasis
stopping bleeding
what are the new blood vessels that can grow into the area of the wound called?
granulation tissue
the capillaries that grow in granulation tissue can help do what in the wound?
oxygenate it and keep it alive
what could potentially go wrong with thrombosis
if it blocks off vessel as this leads to ischaemia (leak of blood flow to tissue) or hypoxia (lack of O2 in tissues)
if it causes stagnant blood to build up behind the thrombus and block blood flow through the vessel
how is excess thrombus/clot removed
fibrinolytic system- removes fibrin and stops thrombi from propagating
plasmin cuts up fibrin into fibrin degradation products
what does the fibrinolytic system depend on?
plasma protein called plasminogen being converted to plasmin
3 things associated with abnormal thrombosis and clotting are called what?
virchow’s triad
abnormalities of vessel wall, constituents of the blood, blood flow
