a heart is a kind of organ & a kidney is a kind of organ in an animal & a bladder is a kind of organ & the heart, blood vessels, kidneys, and bladder work together & blood vessels are a kind of organ -> the heart, bone vessels, kidneys, and compressions rest together is an nation of different ph of mind rest together the heart, blood vessels, kidneys, and bladder working together is an example of different parts of body working together  the heart, bone vessels, kidneys, and compressions rest together is an nation of different ph of mind rest together & an organ system is made of different parts of the body working together -> the heart, blood vessels, kidneys, and bladder working together makes them an organ system