Flashcards in Heamostasis Deck (25):
What is Haemostasis ?
The stopping of a haemorrhage
What are the steps in Hamostasis?
1.Vasoconstriction -Decrease pressure downstream, Doesn't happen at veins
2. Platelet plug formation- Primary Heamostatic plug form activated platelets - seconds
3. Secondary Plug, Fibrin molecules - 30 mins
How can it be assisted?
What is clotting?
Blood becomes solid when into contact with CT. controle by Clotting factors
What destroys clots?
What does not clot blood?
What are the 3 main players ?
Process of blood clotting
What activates platelets?
Collagen surfaces- extravascular
ADP- Amplification and Injured RBC
Thromboxane A2- Platelets aggregator - activated platelets
How do Platelets activate?
1. Sick to sub endothelium with Von Willebrand factor
2. Aggregaten and fibrinogen Binds
3. Swell and change into sticky spheres
4.Secret factors to help growth - Fibrnogen , ATT
What is required in synthesis of blood clotting Factors ?
And what other ?
Cofactors- Phospholipids and calcium
What type of Enzymes are clotting factors and what do they do?
Proenzymes activating the next = Amplification.
what provides surface for clots?
Swelling of platelets during activation
What are the 2 pathways and why are they called what they are?
1. Intrinsic - factors all in blood , no vessels needs to be broken only negative charged surface
2. Extrinsic - Extra cellular Tissue factor (Thromboplastin) Relesed from Damagae cells near site.
Both can clot without platelets but not very well
What happens to Vascular Wall ?
1. Media contracts
2. Sub-endothelium traps
balances fibronlysis and clotting
Factors affecting the formation of clots
1. Anticoagulants - Antithrobin 3, Protein C and S
2. Dilution by increasing blood flow
What causes the evolution of a clot?
Platelets squeezed out by fibrin using actin myosin filaments pushing sides together and squeezing fluid
What are the stages of Fibronolysis?
macrophages break down firbrin and sodeos plasmin . Plasminogen made in liver as is sterpokinase and urokinas . Activated by tPA and the Clotting cascade as Fibrin activates tPA.
FDP is made
What is haemophilia?
Normal platelets but impaired clotting
A: Factor 8 deficiency .
B: Christmas diseases factor 9
Whats does APTT. PT and Bleeding time measure
APTT- Intrinsic pathway
Bleeding time- Platelet plug
What is tissue factor?
Factor 3- Extrinsic
Deficiency in VW factor. Platelet plug and stabilising factor 8 . Prolonged APTT and Bleeding time .
What is Thrombocytopenia?
Platelet too low . Spontaneous bleeding . pronged BT- Petechiae
Cause of Thrombocytopenia
1. Decreased production due to Bone marrow infiltration
2. Decreased Platelet survival
3. Sequestration in spleen
4. Dilatational - Blood Transfusions
What is DIC
Disseminated Intravascular Coagulation . Secondary to underlying cause
Formation of microthrombi. Activates fibrinolysis . Leads to haemorrhage
Transfusion of platelets ,FFP and cryoprecipitate