The document outlines the role of platelets in hemostasis, emphasizing their structure and functions, including adhesion, activation, and aggregation. Key processes involve the interaction of platelets with collagen, von Willebrand factor, and various agonists, which lead to the formation of a hemostatic plug. It highlights the biochemical changes during platelet activation and the formation of bridges between platelets mediated by fibrinogen.

1. HEMOSTASIS

17. Structure of platelet
membrane glycoproteins

20. Composition and function of platelet
alpha granule contents

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

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

27. Platelet activation
 Complex process
 Include changes in
 Metabolic biochemistry
 Platelet morphology
 Surface factors
 Membrane phospholipid orientation

28. Biochemical changes after activation
2
34
5
6 7
8

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