The blood
is the transport system by which oxygen and nutrients reach the body's
cells, and waste materials are carried away. The heart, a muscular organ,
positioned behind the ribcage and between the lungs, is the pump that keeps
this transport system moving.
Blood that is rich in oxygen appears red.
Blood that is poor in oxygen appears
blue.
Blood
leaves the left side of the heart and travels through arteries,
which gradually divide into capillaries. In the capillaries, food and oxygen
are released to the body cells, and carbon dioxide and other waste products
are returned to the bloodstream. The blood then travels in veins
back to the right side of the heart, where it is pumped directly to the
lungs. In the lungs, carbon dioxide is exchanged for oxygen, and this renewed
blood flows back to the left side of the heart, and the whole process begins
again.
To see some amazing facts about the Circulatory System 