If we imagine two systems of pipes, both of different size, meeting at a central pumping station, we can get an idea of the human circulatory system. The smaller pipes are linked to the heart and the lungs while, the larger pipes go from the heart to various other parts of the body.
These pipes are called arteries, veins and capillaries. Arteries are vessels which carry the blood away from the heart. Through Veins the blood comes back to the heart. So, arteries carry pure blood to the various parts of the body, and veins bring back blood loaded with waste products.
The heart acts as the pumping system station. Arteries normally lie deep in the tissues and the blood in arteries is bright red in colour and moves through in spurts. Veins lie close to the skin surface and blood in them is darker in colour and flows more evenly as veins have valves at regular intervals.
Below Arteries and Veins info from Wikipedia (Read More):-
Arteries (from the Greek αρτηρία) are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.
The human main arteries, part of the circulatory system.
The circulatory system is extremely important for sustaining life. Its proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system. In developed countries, the two leading causes of death, myocardial infarction and stroke each may directly result from an arterial system that has been slowly and progressively compromised by years of deterioration.
http://en.wikipedia.org/wiki/Arteries
In the circulatory system, veins (from the Latin vena) are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood. They differ from arteries in structure and function; for example, arteries are more muscular than veins and they carry blood away from the heart.
http://en.wikipedia.org/wiki/Veins
