Haemostasis Flashcards
How are platelets formed?
In the bone marrow by “budding” from megakaryocytes
Distinguish between primary and secondary haemostasis
Primary involves the formation of a platelet plug; secondary involves the formation of a fibrin clot
Substance released from damaged endothelium which induces platelet adhesion (primary haemostasis)
Von Willebrand factor
Which protein complex is responsible for cleavage of prothrombin to thrombin?
Factor Xa, along with it’s co-factor (factor V)
What does thrombin do?
Converts fibrinogen to fibrin
Class of drugs which inhibits factor Xa
NOACs e.g. rivaroxoban
What does fibrin do?
Forms insoluble strands which sit on top of the platelet plug, forming a clot
Signs of platelet plug failure (4)
Bruising and purpura
Mucosal bleeding
Intracranial haemorrhage
Retinal haemorrhage
Examples of mucosal bleeding (4)
Epistaxis
GI bleeding
Conjuctival/retinal
Menorrhagia
Causes of fibrin clot formation failure (3)
Single clotting factor deficiency
Multiple clotting factor deficiencies
Increased fibrinolysis
In what situation would multiple clotting factor deficiencies arise?
Disseminated intrvascular coagulation- all being used up
Describe the process of fibrinolysis (2)
- Tissue plasminogen activator converts plasminogen to plasmin.
- Plasmin breaks down fibrin to form fibrin degradation products.
Screening tests for fibrin clot formation (2)
Prothrombin time
Activated partial thromboplastin time
Naturally-occurring anti-coagulants (2)
Serine protease inhibitors e.g. anti-thrombin III
Protein C and protein S
What is thrombophilia?
Deficiency of naturally occuring anticoagulants (e.g. serine protease inhibitors, proteins C/S) resulting in an increased tendency to develop venous thrombosis
