Overview of Platelet Physiology: Its Hemostatic and Nonhemostatic Role in Disease Pathogenesis

Table 2

A comparison of endothelial and platelet properties (adapted from Warkentin et al., 2003 [21]).

	Endothelium	Platelets
Nucleus	Yes	No
mRNA	Lots	Little but active
Cell dimensions	Highly variable: up to 100 𝜇M length in large vessels	Diameter ~4 𝜇M, volume 7–12 fL; (inversely proportional to platelet count)
Life span	Long (months to years)	Short (7–9 days)
Daily production	Not known	2.5 × 10^11
Circulating	Few	Most (normally 1/3 sequestered in spleen; may become sequestered on activated endothelium)
Diagnostic markers	Indirect and not clinically useful	CBC, peripheral smear, platelet function studies
Origin	Bone marrow	Bone marrow
Storage granules	Weibel-Palade bodies	α granules, dense granules, lysosomes
Partial list of storage components	vWf, P-selectin, multimerin	vWf, P-selectin, multimerin, fibrinogen, PDGF, TGF-β, IL-1, VEGF, angiopoietin, RANTES, PF4, ADP, ATP, serotonin