The Structure and Production of Blood Platelets

Bloodplatelets are small, anucleate cellular fragments that play an essential role in hemostasis. During normal circulation, platelets circulate in a resting state as small discs (Fig. 1.1A). However, when challenged by vascular injury, platelets are rapidly activated and aggregate with each other to form a plug on the vessel wall that prevents vascular leakage. Each day, 100 billion plateletsmust be produced frommegakaryocytes (MKs) to maintain the normal platelet count of 2 to 3 × 108/mL. This chapter is divided into three sections that discuss the structure and organization of the resting platelet, the mechanisms by which MKs give birth to platelets, and the structural changes that drive platelet activation.