Here PMN's that are marginated along the venule wall (arrow) are squeezing through the basement membrane (the process of diapedesis) and spilling out into extravascular space.
High blood pressure is a serious problem for the blood vessels because it causes wear and tear on the endothelial cells that line the inside of the blood vessels.
Now these free-floating platelets don't clump together during regular circulation — that would be terrible — but when the endothelial cells lining a blood vessel wall tear, the underlying collagen fibers are suddenly exposed.
Yeah, the cells, if you think of the walls of the cells, they make the tree strong and there are a couple of chemicals that make up these walls, cellulose and lignin.