Platelet Structure

Platelet membranes are similar to those of other cells and are characterized by phospholipids arranged in a bilayer forming a hydrophobic core. The lipid rafts are capable of lateral mobility and enhance signaling in initial phases of platelet activation, and mediate cytoskeletal reorganization events critical for clot retraction. The interaction of the cytoskeleton with lipid raft microdomains is necessary for sustaining the forces necessary for clot retraction. Under physiologic conditions, β 1 -tubulin is solely expressed as a component of microtubules within megakaryocytes and is essential for the orderly fragmentation of platelets from the megakaryocyte cytoplasm. Platelet mitochondria support the metabolic activities of resting platelets and play regulatory roles in platelet activation and apoptosis. Platelets possess a cytoskeleton on the cytoplasmic side of the plasma membrane composed of actin, spectrin (fodrin), adducin, filamin, and glycoprotein-Ib-IX–V. Platelets have three main types of storage granules: dense, alpha, and lysosomal, and they are heterogeneous in content and morphology.