Haemostasis Flashcards
What can stem bleeding
plug of fibrin
What are the phases of haemostasis
vascular, platelet, coagulation, tissue repair
Where does the vascular phase
endothelial cells inside arteries
What is the function of prostacyclin
reduce spread of platelet aggregation
What is the function of vascular spasm
reduces lumen size of artery
Where does vascular spasm occur
arteries and arterioles
What do endothelial cells release
chemical factors and local hormones
What are endothelins
peptide hormones
What do endothelins stimulate
contraction of smooth muscle
Describe platelet structure
anucleate, flattened discs
What is thrombocytopoiesis
platelet production
Where are platelets formed
bone marrow - large megakaryocytes
What are the phases of platelets
adhesion, activation, aggregation
What are platelets important for
blood coagulation
What does platelets respond to in the adhesion phase?
exposed collagen of basement membrane
WHat stimulates platelet aggregation and secretion
ADP
What cause vascular spasm
serotonin, thromboxane A2
What promotes platelet formation
soluble factors
What is is the platelet plug formed by
positive feedback loop
What does coagulation convert
fibrinogen into insoluble protein fibrin
What does coagulation promote
growth of fibrin network
What pathways is coagulation triggered by
intrinsic, extrinsic, common
Describe the intrinsic coagulation pathway
collagen triggers activation of pro-enzymes
Describe the extrinsic coagulation pathway
release of tissue factor from damaged tissue
Describe the common pathway of coagulation
activation of Factor X
What does Factor X stimulate
prothrombinase
What is the stabilising factor in coagulation
fibrin
What does too much clotting form
thrombus
what substances restrict clot formation
anti-thrombin iii, heparin
Name some disorders associated with haemostasis
deep vein thrombosis, liver function, vitamin K deficiency
What are the symptoms of haemophilia
absent or abnormal clotting
What is deep vein thrombosis caused by
deficiency of anti-thrombin, inactivity
How is haemophilia type A and B inherited
X linked recessive
How is haemophilia type C inherited
autosomal recessive
What von Willibrand’s disease
common inherited bleeding disorder
What does haemophilia normally affect
Factor IX, XI, VIII
