haemostasis Flashcards
how do endothelial cells help to control blood fluidity and flow?
- control the size of blood vessels
- when intact: contributes to preventing clots
- when injured: promote local clotting on exposed basement membrane
what is haemostasis?
a process which causes bleeding to stop
what is the opposite of haemostasis?
haemorrhage
what is the first stage of wound healing?
haemostasis
what happens with the endothelium is injured?
it stops secreting inhibitors and instead secretes Von Willebrand Factor
what are the 3 stages of forming the haemostatic plug?
- platelet adhesion
- platelet activation
- platelet aggregation
what do platelets release?
vasoconstrictors and pro-thrombotic agents
where are megakaryocytes found?
in the bone marrow
what is a thrombocyte?
a platelet
what is thrombocytopenia?
low platelet count in blood
what is platelet activation?
exocytose + change shape + increase respiratory rate
what is the process of platelet activation?
extracellular ADP –> activation of P2Y receptor –> cation flow
what do platelets release during activation?
thromboxane A2 (TXA2)
what is factor Xa?
the activated version of factor X
what are factor V and factor VIII?
co-factors that allow enzymes to function
what is plasma?
fluid portion of the blood
what is serum?
fluid left after clotting
what is thrombosis?
abnormal formation of a clot locally
what is an embolism?
abnormal migration of clot
what are the 2 coagulation cascades?
- extrinsic (tissue factor) pathway
- intrinsic (contact activation) pathway
what are the 3 pathways to activate factor X to factor Xa?
- extrinsic Xase
- intrinsic Xase
- thrombin also activates it
what is extrinsic Xase
tissue factor + factor VIIa
what is intrinsic Xase?
factor VIIIa + factor IXa
what are the 2 coagulation factors?
prothrombin group & thrombin group
what is prothrombin group?
- factors II, VII, IX & X
- they are enzymes
- vitamin K needed for synthesis
- require calcium ions for activation
- stable
what is thrombin group?
- factors I, V & VII
- thrombin activates them
- V & VIII are co-factors
- factor I is fibrinogen
when is thrombin group increased?
in inflammation, pregnancy & with oral contraceptives
what is vitamin K?
- a class of related fat-soluble vitamins
- is required to synthesise enzyme coagulation factors
- essential for gamma-carboxylation of clotting enzymes
what enzyme coagulation factors does vitamin K synthesise?
prothombin II, VII, IX and X
what does plasmin do?
lyses fibrin
what is protein C?
a coagulation inhibitor
what is antithrombin III
peptide in blood made by liver that blocks activity of thrombin
what does vitamin K deficiency lead to?
insufficient clotting
what is vitamin K deficiency caused by?
GI disease or no fat absorption
what prevents the recycling of vitamin K?
warfarin
what is haemophilia A?
a clotting disorder that affects larger blood vessels, joints and muscles and causes wounds to bleed for days
what is haemophilia A caused by?
lack of factor VIII
what type of disease is haemophilia A?
X linked
how do you treat haemophilia A & what are the issues with it?
inject purified factor VIII but it is rare and expensive
what is christmas disease and what is it caused by?
haemophilia B and it is caused by a defect in factor IX
describe the process of inflammation atherogenesis
- monocytes enter lesion
- become macrophages: consume cholesterol esters
- can become foam cells
- can die and release their contents which attracts more monocytes, cytokines and chemo-attractants
describe lipid atherogenesis
- LDL deposits lipids in lesions
- cholesterol esters are oxidised making oxygen radicals
- oxidised lipids are consumed by macrophages
describe endothelium atherogenesis
- endothelium expresses chemoattractants
- when endothelium is lost, collagen stimulates coagulation
- when endothelial is lost, vessel cannot control its dilation
what 3 types of drugs can be given to control blood clotting?
- anti-platelet agents
- anti-coagulants
- fibrinolytics
when are anti-platelet agents used?
to block platelet activation and good for treating arteriole disease
when are anti-coagulants used?
to block production or activity of clotting factors and used to treat venous disease
when are fibrinolytics used?
to dissolve fibrin in arterial disease
what is aspirin?
a cyclo-oxygenase (COX) inhibitor
what does aspirin do?
- blocks formation of thromboxane A2 in platelets
- lengthens bleeding time
- does NOT increase coagulation time
name 2 ADP receptor inhibitors
- prasugrel
- clopidogrel
what conditions can anticoagulants be used for?
- deep vein thrombosis
- pulmonary embolism
name 2 oral anti-coagulants
- dabigatran
- rivaroxaban
what is warfarin?
- vitamin k antagonist
- slow onset (days)
- requires monitoring
what do heparins do?
- inhibit coagulation by inhibiting factor Xa
what are fibrinolytics?
- clot busting drugs
- tissue plasminogen activator
name 2 fibrinolytics
- streptokinase
- urokinase
