ABSTRACT
Platelet aggregations are important in physiological processes such as thrombus and haemostasis. However, these processes are very complicated and many factors and activities occur at the same. For example, physiological response in haemostasis to blood vessel injury involves the cell-cell adhesive platelet aggregation and coagulation. Platelets are tiny oval structure with diameter of 2-4 micrometers. They are active in blood with a half-life of 8-12 days. Nonactive platelets flow free in blood vessels in a dormant state. Activating chemicals such as ADP initiated by injury can induce platelet aggregation in the blood plasma. A platelet’s surface membrane can be altered so that the platelet becomes sticky, and thus capable of adhering to other activated platelets and the vessel walls. Although platelets only consist of about 0.3% in concentration and yet occur in enormous numbers about 250 millions per milliliter (David et al. 2001; Fogelson 1992; Keener & Sneyd 1998). Once triggered by the chemicals, the active platelets start to clot so as to restrict the blood flow at the injury site. To prevent uncontrolled overspreading of activated platelets, a chemical inhibitor, thrombin, is also involved.
