The heart gets its oxygen and nutrients not from the blood flowign through it, but from the coronary arteries which are the first two arteries that come off the aorta. They have a thick muscle layer and 2 elastic layers to resist the high pressure of the blood as it is ejected from the ventricles and to move the blood along as they rebound. One cell thick. So narrow that red blood cells must line up single file. The pressure is so low that there is time for diffusion and gas exchange.
Veins have a thinner muscle layer and less elastic tissue than arteries.
They have valves to help prevent backflow of blood. When the ventricles contract, this part of the cardiac cycle is called systole. When they relax, it is called diastole. This is the basis of blood pressure readings. 120 mmHg - systolic pressure.