Ultra-structurally, endothelial cells contain:
Endothelial cells are the major source of plasma vWF, whereas most factor VIII is synthesized in the liver. vWF is found in the plasma (in association with factor VIII), in platelet granules, in endothelial cells within cytoplasmic vesicles called Weibel-Palade bodies, and in the subendothelium, where it binds to collagen.
Reference-Robbins BASIC PATHOLOGY 10th edition pg-490
Weibel Palade bodies
Langerhan’s granules
Abundant glycogen
Kallikrein