Blood Coagulation Flashcards
Which blood coagulation factors greatly accelerate the reaction rate of the serine proteases factors?
V and VIII
What causes coagulation factors to activate?
tissue damage
What do some factors require in order to be synthesised?
Vitamin K
What are the vitamin K dependent coagulation factors?
II, VII, IX and X
What is the old historical ways to categorising the blood coagulation factors?
Intrinsic, extrinsic and common pathway.
What is the more modern way of categorising blood coagulation factors?
Cell model of Coagulation
What does Tissue factor VIIa (7) complex convert ?
V to Va leading to prothrombin becoming thrombin
What is the role of thrombin in the cell model of coagulation?
Convert factor 8 to 8a, 5 to 5a and 11 to 11a (5, 8, 11) - these all have the response in generating more 10A = more thrombin
What is added on to sufficient thrombin?
Fibrinogen is converted to fibrin and 13 to 13a (fibrin stabilizing factor)
Which factor is fibrin stabilising factor.
13 - 13a
What are the three phases involved in the cell model of coagulation?
Initiation (in vascular endothelial)
Amplification
Propagation
What is the central event in the cell model of coagulation?
Is the production of thrombin which converts fibrinogen to produce the fibrin clot.
Where is the cell model of coagulation finished?
On the platelet surface.
When does the initiation of the coagulation occur?
When tissue factor binds to activated factor VIII, the tissue factor is exposed to the circulating blood by the disruption of the endothelium on the vessel wall following tissue damage
Which factors amplify the whole cascade and result in the generation of large amounts of thrombin ?
VIII, V and XII - these eventually lead to the conversion of soluble fibrinogen to insoluble fibrin.
How are deficiencies in the coagulation factors detected?
Lab coagulation tests.
What is the principle of a blood coagulation lab test?
- add reagent to the patient plasma
- seeing how long it takes patient plasma to clot - generally related to the level of coagulation factors in the plasma.
How is a plasma sample generated for blood factor coagulation examination?
Taking a sample of trisodium citrate blood and separating off the plasma.
What is an important component of coagulation?
Calcium
What is the name of the 2 tests used to universally screen for coagulation factor deficiences?
- One Stage Prothrombin (PT)
- Activated partial Thromboplastin (APTT)
What can unchecked blood coagulation lead to?
Dangerous occlusions of blood vessels such as Thrombosis - if protective mechanisms such as coagulation factor inhibitors, blood flow and fibrinolysis were not in operation.
What are the 4 natural anticoagulants which
Protein S
Protein C
Antithrombin
Tissue Factor pathway inhibitor
What does protein S inhibit?
VIIIa, XIa
What does antithrombin inhibit?
Xa, IXa, XIa
What does protein C inhibit?
This is a cofactor for protein C
What does tissue factor pathway inhibitor inhibit?
Xa, VIII and tissue factor.
What is the main outline of the fibrinolytic system?
Fibrin Lysis
What does the fibrinolytic system help to ensure?
That the fibrin clot formed in response to tissue damage is localised to the site of vessel injury.
That the clot is removed after healing
It involves a number of enzymes that will break down and dissolve the clot once healing has occurred.
What enzyme is involved in the degradation and dissolution of formed fibrin?
Proteolytic enzyme called plasmin.
What does the fibrinolytic system involve from activator to inhibitor?
Plasminogen activators, plasminogen, plasmin (a) and fibrinolytic inhibitors.
What breaks down fibrin?
Plasmin
What is a fibrinogen degradation product example?
D dimer
What does high levels of D dimer in the blood indicate?
Lots of fibrinolytic activity and is one of the tests used to check for excessive thrombocyte formation.
What is the role of fibrinolytic inhibitors?
To keep a delicate balance on the system keeping at bay , inhibiting action of plasmin on fibrin.
