Man - a creature made at the end of the week's work when God was tired.
Mark Twain
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TingooKIDS: Electricity going through your heart makes the muscle cells contract. http://t.co/3iav3s7Z http://ow.ly/1k9zTK

Electricity going through your heart makes the muscle cells contract.
http://goo.gl/1EdLu

TingooKIDS: http://t.co/N87uJknd : You might have felt your own heart beating, this is known as the cardiac cycle. W... http://ow.ly/1k9jwv

http://goo.gl/L8uhf : You might have felt your own heart beating, this is known as the cardiac cycle. When your heart contracts it makes the chambers smaller and pushes blood into the blood vessels. After your heart relaxes again the chambers get bigger and are filled with blood coming back into the heart.

TingooKIDS: There are four valves in the human heart, they ensure that blood only goes one way, either in or out. ht... http://ow.ly/1k8Zmb

TingooKIDS: http://t.co/Ba1gHttY: Blood going towards the heart is carried through veins. Blood coming from the lung... http://ow.ly/1k8Zm9