Some facts to ponder, from one of the medical blogs I read :-
All of the blood vessels in your body, including arteries, veins and capillaries, are more than 60,000 miles long.
An adult heart pumps approximately 2,000 gallons of blood each day
The heart beats about 100,000 times each day
An average human heart beats more than 2.5 billion times in 70 years
Blood takes about 20 seconds to circulate throughout the entire vascular system
And we take it all for granted...... Blessed art thou, O Lord !