Lecture 21: Blood clotting and blood groups Flashcards
What is the process of platelet formation called?
What stimulates this?
What is the function of platelet formation?
The process of platelet formation is called thrombopoiesis
- process is stimulated by thrombopoietin
Function: Haemostasis and blood clotting/coagulation
How is a platelet plug formed?
- When tissue is damaged, collage from the sub endothelium is exposed and receptors on the platelets bind to this = aggregation
- This causes them to change shape; releasing ADP and thromboxane A2(activation) and the platelets begin to bind to each other = agglutination
—–> platelet plug
ADP and thromboxane also stimulates vasoconstriction, which reduces further blood loss
What are the two main clotting pathways ?
How do they differ?
What do both of these pathways result in?
INTRINSIC pathway = everything needed in INSIDE the blood
EXTRINSIC pathway = the factors needed are located OUTSIDE the blood
Both pathways result in the activation of factor X which activates prothrombin activator - trigger for stages I & II
What occurs during STAGE I of the clotting cascade?
What is required?
- Construction of blood vessels
- Formation of platelet plug
The intrinsic & extrinsic pathway activate factor X which activated prothrombin activator - triggers stages I & II
What occurs during STAGE 2 and # of the clotting cascade?
STAGE 2 catalyses the formation of thrombin from prothrombin which uses Ca ions as cofactors
prothrombin —————–> thrombin
STAGE 3 catalyses the formation of fibrin from fibrinogen resulting in the formation of a blood clot
FIbrinogen —————-> FIbrin
What factors oppose coagulation?
- To limit aggregation endothelium can excrete:
Prostacyclin and or nitric oxide - To limit blood clotting endothelium can excrete:
Tissue factor pathway inhibitor - inhibits extrinsic pathway - There are a numbers of drugs:
Warfarin, Aspirin and Heparin
What is the mechanism called which dissolves clots?
How are clots dissolved?
= FIBRINOLYSIS
Plasminogen is activated by tissue Plasma Activator t-PA, lysosomal enzymes and Factor VII form plasmin. This hydrolyses fibrin to dissolve the clot
What are the characteristics of Type A red blood cells?
- Antigen A
- B Antibodies
= Receives A or O
What are the characteristics of Type B red blood cells?
- Antigen B
- A antibodies
= Receives B or O
What are the characteristics of Type AB red blood cells?
- Antigen A and B
- no antibodies
= Receives all blood types
What are the characteristics of Type O red blood cells
- Antigen free - neither A nor B
- A and B antibodies
= ONLY receives O
D antigen( Rh+) is present in 85% of the population and there are NO preformed antibodies . What are the problems that occur is a Rh- mother receives Rh+ blood from a foetus?
If a Rh- patient receives Rh+ blood they will develop anti-Rh antibodies.
- during childbirth some RBCs from foetus cross the placenta. The mother would then being to synthesis anti-Rh antibodies. The first foetus is unaffected but the second baby is at risk
- —-> Give mother anti-D antibody at first delivery to prevent antibody development.