There is no transportation system in any city that can compete in efficiency with the circulatory system of our body. If you can imagine two systems of pipes, one large and one small both meeting at a central pumping station, you will have an idea of the circulatory system. The smaller pipes go from the heart to the lungs and back, while the larger once go from the heart to the various other parts of the body of the body. These are called arteries, veins and capillaries.
Arteries are vessels in which blood carried away from the heart in veins, the blood is coming back to the heart. In general terms, arteries are carrying pure blood to various parts of the body, and the veins are bringing back blood loaded with waste products. The pumping station is of course the heart.
Arteries lie deep in the tissues, except at the wrist, over the instep, at the temple and along the sides of the neck. At any of these places the pulse can be felt, which gives the doctor an idea of the condition of the arteries. The blood in arteries is bright red in color and moves through in spurts.
Veins lie closer to the surface of the skin, and the blood in them is much darker in color and flows more evenly. Veins have valves at intervals all along their course.