Understanding Circulation

Understanding Circulation

Outline of human figure showing veins, arteries, kidneys, and heart. Veins are superior vena cava above heart, inferior vena cava below heart, femoral vein in thigh, and greater saphenous vein in calf. Arteries are ascending aorta above heart, abdominal aorta in abdomen, iliac artery in pelvis, femoral artery in thigh, and popliteal artery in lower leg.
Some of the body’s major arteries and veins are labeled above.

Blood flows from the heart to the body and back to the heart. This non-stop flow is called circulation. Blood flows through blood vessels. These are hollow muscular tubes. There are three main types of blood vessels.

  • Arteries are vessels that carry oxygen-rich blood away from the heart.

  • Veins are vessels that return oxygen-poor blood to the heart.

  • Capillaries are tiny blood vessels that connect arteries and veins.