4. Physiology           4.4. Haematology             
 4.4.1. Haemostasis          Clot formation Platelet plug
formation  A.1.2. Temporary platelet plug formation  3 stages:
1. Platelet adhesion   2. Platelet activation   3. Platelet
aggregation  A.1.2.1. Platelet adhesion  When blood vessel
injured --> Platelet adhere to exposed collagen and vWF via
receptors on membrane --> Binding activates platelets  Adhesion
mechanism  2 mechanisms:    • Adhesion to collagen is
facilitated by glycoprotein Ia (on the membrane)   • Adhesion to
vessel wall vWF is by glycoprotein Ib-IX complex (on the
membrane)     * vWF = von Willebrand factor  A.1.2.2. Platelet
activation  Platelet activation can be induced by    • Adhesion
to proteins such as collagen, soluble agonist (epinephrine, ADP,
serotonin, thrombin)   • Cell contact during platelet
aggregation   • Platelet-activating factor (PAF)     * A
cytokine secreted by neutrophils, monocytes, and platelets     *
Also has inflammatory activity     * Acts via G protein-cou