Whats the main organ of the ciculatory system

The very main Organ of the Circulatory system is the "Heart"

It Pumps blood through out your system keeping it well maintained with oxygen and taking wastes away from cells. 

love, the Pineapple :)
<3

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.