High blood pressure means that blood is pushing too hard against artery walls. The force of this blood can damage the delicate inner lining of the artery walls.
If this inner lining is damaged, fat and calcium can build up in the artery wall, forming a plaque. This plaque makes the artery stiff (atherosclerosis). This is also called "hardening of the arteries." The plaque might narrow the artery. This narrowing could reduce the amount of blood that is flowing through the artery. Over time, plaque can cause problems throughout the body.