Hemostasis is the arrest of bleeding, whether it be by normal vasoconstriction (the vessel walls closing temporarily), by an abnormal obstruction (such as a plaque) or by coagulation or surgical means (such as ligation)
22. PLATELET ROLE IN HEMOSTASIS
Perform surveillance of blood vessel continuity
Platelet-platelet interactions[primary hemostatic plug]
Platelet – coagulation protein interactions[secondary
hemostatic plug]
Aid in healing injured tissue
23.
24. Platelet adhesion
It is the attachment of platelets to collagen and other
components of endothelium.
Platelets contain 2 collagen receptors :GPIaIIa and
GPVI which mediate direct collagen binding at low
shear rate.
Platelets adhesion to collagen at high shear rate
however requires the presence of VWF and the
platelet VWF receptor,GPIIb/IX
25.
26.
27. Platelet activation
Complex process
Include changes in
Metabolic biochemistry
Platelet morphology
Surface factors
Membrane phospholipid orientation
30. Platelet aggregation
Newly arriving platelets flowing into the area become
activated by contact with agonists
such as ADP and thromboxane A2[released
by the initial adherent and activated platelets]
Products from the damaged tissue and
endothelial cells.
Thrombin[a procoagulant enzyme generated
by tissue factor /F-VIIa]
Mediated by fibrinogen which forms bridge between
platelets via Gp IIb Gp IIIa