In single celled bacteria and other small organisms, the respiration process of gas exhange can happen through simple diffusion. In large organisms, however, this is impossible, because a very small amount of cells in large organisms are located close enough to the surface for diffusion to take place. Two major changes made it possible for all organisms to attain multicellularity. One being an efficient circulatory system to transport gases to and from all tissues in the body. The other is a large respiratory system. The respiratory system centralizes the responsibilty of

Lungs also have several jobs that do not include the respiratory function. A main job for the lungs is to protect the heart. They surround the heart and act as cushions to soften any blow that the heart may have to endure. Without this padding, simply bumping into someone could be fatal. Another responsibilty of this organ is to influence the concentration of biologically active drugs and other substances which are used in medicine. Filtering out small blood clots formed in the systemic veins is another task performed by the lungs.
About the Author

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Tyler Brooker is the owner and operator of Lungs Spot - http://www.lungsspot.com, which is the best site on the internet for all lungs related information.