Hemostasis. Characteristics of platelets. Formation of platelet plug. Flashcards
hemostasis - definition
preventing excessive blood loss
whilst ensuring blood is flowing around the body
hemostasis - step 1
vasospam
right after cut the blood vessels constrict their flow to prevent blood from flowing to broken area causing blood loss
- smooth muscle contraction
- cell signalling molecule of endothelial to release NO + PROSTACYCLIN 2 = anticoaggulants
hemostasis - step 2
platelet adhesion
exposed platelets are adhered together
- von willebrand factor
- subendothelial collagen
hemostasis - step 3
platelet activation
platelets release chemical granules
- serotonin
- ADP
- thromboxane A2
to form positive feedback mechanism to amplify response
hemostasis - step 4
platelet aggregation
GPIIb/IIa receptors + fibrinogen = formation of primary platelet plug
hemostasis - step 5
extrinsic pathway
caused by subendothelial cells + exposed tissue factor
factor 3 -> factor 7 -> factor 7a -> factor 10 -> factor 10a (enters common pathway)
hemostasis - step 6
intrinsic pathway
cause = bloods platelet gets into contact with collagen fibres + damaged blood vessel =
factor 12 -> factor 12a -> factor 11
factor 11a -> factor 9a + factor 13a = tenase complex formation on surface of activated platelets
factor 10 -> factor 10a = common pathway
hemostasis - step 7
common pathway
extrinsic (initial) + intrinsic (amplifier) activated by factor X
1 - factor 10a + factor 5a converts prothrombin into thrombin
2 - fibronogen converted to fibrin via thrombin
3 - fibrin formed meshwork clot
hemostasis - final stage
clot retraction
removal of fibrin clot
- dissolved by fibrinolysis
- plasminogen activator
platelets - 1
- diameter = 3mm
platelets - 2
resting state = flat
active = spherical
platelets - 3
TPO mechanism
platelets - 4
anucleated
rich in cytoplasm
lysosomes
