Haemostasis Flashcards
What is haemostasis?
The arrest of bleeding in the body
What are the characteristics of the haemostatic system?
Permanently ready
Prompt response
Localised response
Protection against unwanted thrombosis
What are the 4 components of the haemostatic system?
Platelets
Clotting factors
Fibrinolysis factors
Anti-coagulant defences
What type of cell forms platelets?
Megakaryocytes
What is the mean life-span of a platelet?
7-10 days
What factor is released by collagen to stimulate a primary response?
Von Willebrand Factor
What occurs during primary haemostasis?
Endothelial damage exposes collagen
Collagen releases Von Willebrand Factor
These bind to platelets
Platelets then release chemicals such as ADP and Thromboxane A2 which recruit other platelets for aggregation
What is an example of a disease that decreases collagen levels in the endothelium, therefore decreasing the primary response?
Scurvy
What is an example of a disease that effects platelets?
Thrombocytopenia - a reduced number of platelets, usually caused by bone marrow cancers
What is Von Willebrand’s disease?
An inherited disease that leads to a decrease in levels of Von WIllebrands Factor
What is purpura?
A fine rash
What is the medical term for a nose bleed?
Epistaxis
What is the medical term for heavy menstrual bleeding?
Menorrhagia
What are some consequences of failures of the primary haemostatic system?
Spontaneous bruising
Purpura
GI bleeding
Conjunctival bleeding
Menorrhagia
Epistaxes
Intracranial haemorrhage
Retinal haemorrhage
What are the 2 pathways of secondary haemostasis?
Intrinsic and extrinsic
What occurs in the intrinsic pathway of secondary haemostasis?
Calcium from the platelets moves to the cell surface, allowing the negatively charged factors to bind
What occurs in the extrinsic pathway of secondary haemostasis?
Calcium from the platelets moves to the cell surface, allowing the negatively charged factors to bind
What occurs in haemophilia a?
There is a deficiency of factor 8
What occurs in haemophilia b?
There is a deficiency of factor 9
What factor converts prothrombin to thrombin?
Factor 10a and 5
What does thrombin cause?
The conversion of fibrinogen to fibrin
What are the consequences of failures of secondary haemostasis?
Joint and muscle bleeding
What occurs in fibrinolysis?
Tissue plasminogen activator converts plasminogen to plasmin
Plasmin then breaks down fibrin into D-dimers (Fibrin Degradation Products)
What occurs in natural anti-coagulation?
Anti-thrombin III is the main natural anti-coagulant
This binds to, and inactivates thrombin
This stops formation of the fibrin complex and factor 8 and 9 activation
Protein C turns off factors 8 and 9
Protein S turns off factors 10 and 5
