Clotting Lab Flashcards
haemostasis
the stopping of bleeding, blood clotting is a part of haemostasis, prevent major blood loss
3 phases of haemostasis
vascular spasm, platelet plug formation and coagulation
vascular spasm
contraction of the smooth muscle vessel wall triggered by neural flexes which slows blood loss
platelet plug formation
temporary seal for blood loss.
- platelets stick to exposed collagen and connective tissue
- platelets become activated and release chemicals activating passing platelets
- plug formed
coagulation
formation of clot regulated by clotting factors
platelet
develop from hemopoietic stem cells
intrinsic pathway
triggered by internal damage to the vessel wall.
slower and involves more steps
extrinsic pathway
triggered by tissue damage (external)
faster and less steps
how is factor XII activated
(intrinsic pathway)
(intrinsic pathway)
activated once it comes into contact with negatively charged collagen on the damaged endothelium, triggering the cascade
factor VIII
factor that platelets release to facilitate further clotting
production of thrombin
factor IX combines with factor VIII to form an enzyme complex that activates factor X (which along with factor Va produces thrombin)
factor VII
exits the circulation into surrounding tissues when blood vessel is damaged
tissue factor (factor III)
released by damaged cells into circulation
TF-VIIa complex (factor III and factor VII)
activates factor X which activates thrombin
final common pathway
both pathways converge at conversion of factor X to factor Xa (activated)
inactive prothrombin to
thrombin
soluble fibrinogen to
fibrin
APTT assay
measures how long it takes to form a blood clot (intrinsic pathway) used to find problems with forming blood clots/ blood conditions
haemophilia B
IX deficiency
haemophilia A
VIII deficiency
thrombophilia
forms clots more easily
fibrinolysis
where the protein plasma removes a blood clot
plasminogen
synthesised in the liver and circulates in plasma
tPA
converts plasminogen to plasmin which breaks down the fibrin mesh
vitamin K
used by the liver for clotting factor synthesis
fibrinogen
factor I
stabilising factor
factor XIII
