The human body.
No machine can match the feats it performs every day.
Our lungs suck in 70 quarts of air each minute when we exercise.
Our hearts pump two thousand gallons of blood each day...
and more than 600 muscles keep us moving, in every direction.
Like all living things, human beings are made up of cells...
100 trillion of them.
Individual cells are organized into tissues...
like this heart muscle tissue.
Different kinds of tissue form an organ, such as the heart.
And several organs working together create an organ system.
Each of the 10 major organ systems in the human machine
performs a special job.
The circulatory and respiratory systems supply energy 24 hours a day.
The heart works automatically, and incredibly hard.
No other muscle in the body is as strong.
It beats 100,000 times a day... 36 million times a year,
sending blood on a complete trip around the body in less than a minute.
The lungs pull in oxygen from the air,
delivering breath through 1500 miles of airways.
All this work is fueled by food...
and turning pizza into usable molecules
is the job of the digestive system.
Swallowing sends food down the esophagus into the stomach.
Like a blender, the stomach contracts to break it down,
helped out by acid and enzymes.
This liquefied food travels into the small intestine,
which can be over 20 feet long,
where most nutrients enter the bloodstream.
And the brains of this whole operation...
is the human brain.
A wrinkled blob about the size of a grapefruit,
it's the most complex object on earth.
The brain contains up to 100 billion neurons, or nerve cells.
Neurons send signals rocketing through the brain
at over 200 miles an hour.
The brain, spinal cord, and nerves make up the nervous system
and all work together to control the body's activities.
The reproductive system creates new life.
Each human begins as two single cells:
an egg cell from the mother, and a sperm cell from the father.
When these two cells meet, they begin to divide...
and over 9 months, a whole new person is formed.
Strands of DNA carried in the original two cells
act like a set of blueprints, telling the cells to build a person
with brown eyes, curly hair, or a wide smile.
The end result of all this genetic scrambling...
bodies that take us on a miraculous journey every day.
They allow us to push the frontiers,
meet awesome challenges,
and expand the boundaries of human achievement.