YOU HAVE TO HAVE A SYSTEM
    Actually you are visualizing just one very important system, which affects all of the other systems of the body.  The job it performs is very involved with a tight deadline.  In order for it to work efficiently, it has to be right on target.  Some of the other systems are directly connected to the heart, while others are only remotely connected.  Actually the human body uses many systems that work side by side.
    Of course the heart is like the president of the organization.  It may not be directly involved with every single system, but still plays a part in the overall production.  Obviously, if the heart isn't working properly, nothing else is either.  The heart participates in the circulatory system, as it keeps a watchful eye on the respiratory and excretory system as well.