<prompt> Delayed prolonged bleeding is caused byHistamineLeukocyte dependent injuryIL-IDirect injury to endothelial cells  <response>: EndotheliumDirect injury to endothelial cells causes delayed prolonged bleeding because, endothelial cells are central regulators of hemostasis, the balance between the anti-and prothrombotic activities of endothelium determines whether thrombus formation, propagation or dissolution occurs.Robbins basic pathology 9th edition page no 79 