Circulatory System

Diffusion alone is not sufficient enough for the transporting of substance over long distances. The time it takes for a substance to diffuse from one place to another over a long distance is proportional to the square of that distance. The circulatory system solves this problem. The circulatory system rapidly transports fluids in bulk throughout the body. This system exchanges gases, absorbs nutrients, and disposes waste. The vertebrate circulation is called the cardiovascular system. The heart pumps blood through the blood vessel channels and delivers it to various parts of the body. Arteries carry blood away from the heart. They divide up into aterioles which are small blood vessels. From aterioles capillaries are formed. They are the smallest vessel to carry oxygenated blood. Different species of vertebrates have slightly different heart forms. Fish have a two chambered heart. Amphibians and reptiles have a three chambered heart. Mammal and birds have a four chambered heart. These hearts may have different structures but they all provide basically the same function.