<prompt> Ultra structurally , endothelial cells containWeibel palade bodiesLangerhans granulesAbundant glycogenKallikrein  <response>: ref Robbins 9e p76 Weibel-Palade bodies WPBs are the storage granules of endothelial cells, the cells that form the inner lining of the blood vessels and hea. They store and release two principal molecules, von Willebrand factor and P-selectin, and thus play a dual role in hemostasis and inflammation. 