Circulatory Disturbances II Flashcards
What is haemostasis?
Ceasation of blood loss in vessel wall disruption via localised interaction between endothelium, platlets and coagulation factors
How does primary haemostasis occur?
- Recruiting of platlets
- Platlets adhere
- Phospholipid complex expression
- Granule release ADP/TXA2
- Recruitment
- Aggregation of primary heamostatic plug
What is the mediator of the coagulation cascade in haemostasis and where is it produced?
Tissue factor produced by damaged endothelium is the major activator of the extrinsic pathway of the coagulation cascade
What are coagulation factors? give examples
Plasma proteins produced by the liver (mostly):
- Structurally related/functionally interdependent e.g. factors XI, XII, HMWK
- Vitamin-K dependent e.g. factors II, VII, IX, X
- Highly labile fibrinogen group e.g. factors I, V, VIII, XIII
What is fibrinolysis?
Mechanism to breakdown the fibrin/platlet clot restricting haemostasis to the site of injury
What is a haemorrhage and what does it cause? How do haemorrhages occur?
Extravasation of erythrocytes into the extravascualr space causing:
Rhexis - physical vessel wall disruption or diapedesis - no wall disruption but less RBCs csn escape
Abnormal function of endothelium/blood vessels, platlets or coagulation factors can be inherited or aquired
What are the different types of endothelial abnormalities relating to haemorrhage?
- Endothelial injury
- Developmental collagen disorders
- Collagen defects in guinea pigs and primates with vitamin C deficiency
- Thrombocytopaenia - reduced platlet count
- Thrombocytopathy - abnormal platlet function
- Reduced concentration or function of coagulation factors
How does reduced platlet numbers occur?
- Reduced platlet production (megakaryocyte damage)
- Increased destruction of platlets by immune-mediated disease
- Increased use of platlets in diffuse endothelial damage or generalised platlet activation
How does decreased concentration of coagulation factors occur?
- Inherited deficiencies of CFs
- Decreased production of CFs in severe liver disease
- Decreased production of vitamin K dependent CFs
- Increased use of CFs due to increased consumption associated with DIC
How do we classify haemorrhages based on size? give 3 examples
Depending on cause, location and severity:
Petechiae - 1-2mm in skin, mucous membranes or serosal surfaces via diapedesis in minor vascualr damage
Eccymoses - up to 2-3cm in more extensive vascular damage
Suffusive - larger continous areas of haemorrhage
What is the significance of haemorrhages?
Most commonly local and stopped via haemostasis or local extravascualr tissue pressure matching the intravascualr pressure to end haemorrhage
Significance depends on Volume, Rate and Site
What is thrombosis?
Formation of an excessive or inappropriate clot on the endothelium of a blood or lymphatic vessel or within the heart
What is an infarction?
Area of peracute ischemia that undergoes coagulative necrosis as a result of occlusion of blood vessels by emboli, vasospasm, vascular compression, torsion or rupture
What are the 3 major determiannts of thrombosis?
Endothelial injury
Abnormal blood flow
Hypercoagulabilty
How does endothelial injury cause thrombosis?
Damaged endothelium is prothrombotic meaning that it causes synthesis of tissue factor activating the extrinsic clotting cascade producing vWF which leads to platlets adhering to the exposed subendothelial collagen
