Lecture 9 - Haematology II Flashcards
What is the homeostatic response?
Involves vasoconstriction, platelet adhesion + aggregation and clotting/coagulation
Occurs all at once and not really in order
What is the structure of platelets?
Small
Oval shaped
Contains granules
Where to platelets come from
Megakaryocyte
Production is controlled by circulating platelets and the release of thrombopoietin
What is the lifespan of platelets?
7-10 days
How does platelet adhesion and aggregation occur?
Vessel injury causes collagen exposure and platelet adhesion
This activates the platelets which undergo a shape change, secrete granules and activate GPIIb
This leads to production of thromboboxane and ADP which leads to aggregation which leads to contribution of the primary then stable haemostatic plug
How does vasoconstriction occur?
Vessel injury causes vasoconstriction which reduces blood flow
This allows the primary the stable haemostatic plug to form
Serotonin and Thromboxane from platelet activation contribute to vction
What are the three pathways of the blood coagulation cascade?
Extrinsic
Intrinsic
Common
What is the extrinsic pathway in blood coagulation?
The tissue factor is formed when the blood vessel is damaged
Initiates coagulation
Binds to clotting factor VII which forms factor VII tissue factor complex
The complex binds to factor X which is activated into FXa
What is the intrinsic pathway in blood coagulation?
Factor XI and its cofactor VIII activate many FX to become FXa
What is the common pathway of blood coagulation?
Prothrombinase activates prothrombin to form thrombin
Thrombin converts fibrinogen to fibrin which helps from the stable haemostatic plug
What is the role of calcium and vitamin K in blood clotting?
They’re needed for almost every aspect
What are three ways clotting is controlled?
Anticoagulants
Antithrombin which inhibits thrombin
Heparin which is released by basophils and mast cells and accelerates the actions of antithrombin
What is fibrinolysis?
The fibrin clot is broken down by plasmin
This produces fibrin degradation products
How are blood groups determined?
Genetics
Antigens on the red blood cell membrane
Which blood types are dominant and recessive?
A and B = dominant
O = recessive
