Bleeding & Clotting Flashcards
(31 cards)
What are the 3 processes that stop bleeding?
- Vasoconstriction
-Platelet plug - Coagulation
What happens in the platelet cascade?
Conformational change to spike shape
Granules move to surface
Release of ADP & TxA2
Signal other platelets to clot
What is the role of factor 10? Where is it made?
Cleaves prothrombin to thrombin (activates fibrin)
Liver
What factors are involved in the intrinsic pathway?
8, 9, 11, 12
What factors are involved in the extrinsic pathway?
7
Where’s tissue factor found?
Injured endothelium
TF bearing fibroblasts & monocytes
Describe the common pathway
Factor 10 activated to 10a
Causes prothrombin to become thrombin
Causes fibrinogen to become fibrin
What’s needed to help activate factor 10?
Calcium
Lipids
Factor 5
Which factors require vitamin K?
2, 7, 9, 10, protein C & S
What’s the role of t-PA?
Converts plasminogen to plasmin causing the breakdown of fibrin
Which part of the coag pathway does PT & APTT assess?
PT: Extrinsic
APTT: Intrinsic
What prolongs INR?
Vit K deficiency
Warfarin
DIC
Liver disease
What can prolong APTT?
Heparin treatment
Haemophilia
DIC
Liver disease
What can cause decreased production of platelets?
- Aplastic anaemia
- Marrow infiltration (myeloma, leukaemia)
- Marrow suppression (chemo, RT)
What causes increased platelet destruction?
- Immune thrombocytopenia (SLE, CLL, drugs, viruses)
- Non immune (DIC, HUS)
What are the causes of poor functioning platelets?
- Myeloproliferative disease
- NSAID
- Inc urea
What are the common coagulation disorders?
Congenital: Haemophilia, vWD
Acquired: Therapy, Liver disease, DIC
How is Haemophilia A passed?
X-linked (to males)
Why is von Willebrand factor important?
Important in platelet adhesion to collagen & other platelets
What are the causes of thrombophilia?
Inherited: Factor V Leiden, Protein C&S deficiency, antithrombin 3 deficiency
Acquired: Antiphospholipid syndrome, SLE, COCP, HRT, polycythaemia, malignancy, pregnancy, obesity
Which blood groups have a higher clotting rate?
A
B
AB
What are the 3 steps of the coagulation phase
- INITIATION: Formation of prothrombinase
- AMPLIFICATION: Activation of platelets by coagulation factors & thrombin
- PROPAGATION: Massive thrombin burst converting fibrinogen to fibrin
How does the cell based coagulation model initiation phase work?
1) Partial activation on platelets by TF releases vWF which attaches platelet to subendothelial collagen
2) Externalization of plasma membrane phosphatidylserines provides scaffold for coagulation complexes
3) Circulating factor 7 attaches to TF
4) Factor 7a/TF complex activates factors 9 (on plt surface) & 10 (at TF site)
5) Factor 10a activates factor 5
6) Factor Factor 10/5 complex becomes prothrombinase
How does the cell based coagulation model amplification phase work?
1) Occurs on surface of plts
2) Prothrombinase converts prothrombin into thrombin
3) Thrombin activates factors 5, 8, 10, 11
4) Factors fully activate platelets
