Blood vessels are of two types. They are arteries and veins. Arteries are blood vessels that carry oxygenated blood from the heart to all the organs and parts of the body. However, there are two exceptions. The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs. Also, the umbilical arteries (paired arteries) in a pregnant woman carry deoxygenated blood from the fetus to the placenta. These umbilical arteries surround the urinary bladder and they regress after the birth of the child. Generally, arteries are of three types. They are elastic arteries, muscular arteries, and arterioles. Arteries have a higher blood pressure when compared to other circulatory systems and it depends upon the cardiac cycle. While the aorta is the root systemic artery, the capillaries are the smallest blood vessels which form the microcirculation system. Complications of the arteries include atherosclerosis, coronary artery disease, aortic aneurysm, peripheral vascular disease, atheroma, and complications of diabetes.