Your arteries bring blood from your heart out into your body, giving your organs and tissues the oxygen and nutrients they need. Once your organs and tissues get the oxygen and nutrients, blood returns to your heart through your veins. When your blood vessels are healthy, flexible, and smooth, blood can move through them easily and keep your organs and tissues working the right way. But if your blood vessels are hard, narrow, or blocked by plaque, blood cannot flow the way it should. This means that your organs and tissues can’t get the nutrients they need, which can cause a range of symptoms and even lead to serious health problems.