Function of the Heart:

Every cell in your body needs oxygen in order to live and function. The role of the heart is to deliver the oxygen-rich blood to every cell in the body via the circulatory system.

The Heart:

The heart has three functional systems:

• Pump
• Electrical system
• Coronary system

The heart is divided into two separate sides or circulations:

• Right side (oxygen poor "blue" blood):
  Accepts blood from the body and pumps it to the lungs
• Left side (oxygen rich "red" blood):
  Accepts blood from the lungs and pumps it to the body

Each side has it's own:

• Collecting chamber - Atrium
• Pumping chamber - Ventricle

To keep blood flowing in the proper direction, "check valves" separate the various chambers.

You can find further information here: The American Heart Association Website