Heart, Front View

The external structures of the heart include the ventricles, atria, arteries and veins. Arteries carry blood away from the heart while veins carry blood into the heart. The vessels colored blue indicate the transport of blood with relatively low content of oxygen and high content of carbon dioxide. The vessels colored red indicate the transport of blood with relatively high content of oxygen and low content of carbon dioxide.

Venous Insufficiency

The valves in the veins usually channel the flow of blood toward the heart. When these valves are damaged, blood leaks and pools in the legs and feet. Venous insufficiency is a condition in which the veins fail to return blood efficiently to the heart. This condition usually involves one or more veins. Symptoms include swelling of the legs and pain in the extremities such as a dull aching, heaviness, or cramping.