Incredible Human Machine

There is nothing more familiar

or more mysterious...

more breathtaking in its action...

marvellous in its mechanics...

exquisite in its range of senses...

and staggering in its ability to understand.

On a fantastic voyage

through a single day,

we plunge deep into the routine miracles

of the human body.

Dream on, dream on...

Our instruments,

engines,

infrastructure,

roadways and circuitry.

Through 1 0,000 blinks,

20,000 breaths,

1 00,000 beats...

Hello.

..today is an ordinary, extraordinary day

in the life of the incredible human machine.

Bits of stardust is really all we are.

Oxygen, carbon, hydrogen

and a handful of elements that would cost

very little at any chemical supply shop.

But get these chemicals together,

marinate in a hospitable place

for about 3.8 billion years

and the mundane mix of molecules

becomes precious.

There are more than six billion human bodies

living on Earth

and each of us is the amalgamation of

some 1 00 trillion microscopic cells.

While the blueprint for each individual

are 99.9 per cent identical,

no two of us are exactly the same.

As a new day dawns,

each human machine begins

the succession of miracles

that will take it from morning to midnight.

Cells, senses,

muscles, bones,

hearts, brains,

all must marshal their forces and unite

just to wake us up.

(Alarm beeps)

(Sighs)

At the surface of it all,

a velvety overcoat of cells and protein

keeps us in

and the rest of the world out.

lt's our armour,

our radiator,

our entree to pain and pleasure.

lt is the body's largest organ -

our skin.

Smooth and silky to the eyes and touch

a closer look

presents a very different landscape.

Magnified 600 times,

our outermost skin is nothing but dead cells,

riddled with ridges and grooves

and pocked with countless bumps

and holes.

Look closer still and we find

hundreds of thousands of bacteria

inhabit every square inch of us.

With every tick of the clock,

our dead skin gets sloughed off.

We shed at least 600,000 particles of skin

an hour-

about a pound-and-a-half's-worth each year,

which accounts for as much as 80 per cent

of the dust in our houses.

But there's plenty of skin to go around.

lf we could peel it off and lay it out flat,

the average person's skin

would cover some 1 8 square feet.

Though just millimetres thick,

it would weigh about 6lb.

And we're constantly making more.

Just wait a month or so

and you'll have a shiny new coat.

Which means skin can't be all dead.

Dip below the surface

and you find cells continuously dividing

to replace those dead cells above.

Kilometres of blood vessels

pulse to skin's connective tissues.

Not forgetting

all those precious nerve endings.

45 miles-worth of nerves stretch

from our heads down to our toes,

and many reach to our skin.

Some parts more than others.

lf sensitivity were size-dependent,

we would look something like this.

Our supersensitive hands, feet,

tongue and lips,

each packed with touch receptors,

would swell enormously.

Our legs, on the other hand,

would resemble a chicken's.

Good thing for us there is more to this organ

than touch.

Skin is also our heating and cooling system.

And by helping maintain

that comfy 98.6 degrees Fahrenheit

it keeps us alive.

Through its network of blood vessels,

skin carries as much as one-third

of the heart's hot, freshly-pumped blood.

Get too hot and these vessels can widen

to release heat from our bodies.

But sometimes that's not enough.

A good workout can raise the body's

temperature several degrees above normal -

a potentially deadly state

if it weren't for skin's slick safety net..

sweat.

More than two million holes across our skin

can produce up to half a gallon of the liquid

in an hour.

The heated droplets evaporate into the air,

and leave the body cool.

Through a special camera that images heat,

not light,

we can see this air-conditioning system at work.

The hotter the body, the deeper the red.

No surprise, some of the warmest parts

of our bodies -

our foreheads, palms, and armpits -

correlate with the greatest concentration

of sweat glands.

But we're more likely to encounter the opposite

extreme in our morning routine.

Exposed to a chill,

tiny musclesjerk our hairs to attention,

bulging the skin around them.

We call them goose bumps.

Scientists have dubbed us ''the naked ape''.

But look closely

and we find we're anything but naked.

Some of our skin cells form tubes

that produce hair.

And we have as many of these follicles

punctuating our skin

as do our hairy relatives.

Some five million of them.

As the new hair cells divide,

they push old ones up and out.

By the time our hair breaches the surface,

it's dead.

Which is why we don't feel pain

with every haircut.

Cleaned and groomed,

we venture into the bustling morning world.

Around us, other incredible human machines

greet the day,

in all different sizes and shapes,

colours and textures.

But on some level, we all inhabit the same skin.

Below the surface, each of us has

about the same number of melanocytes,

the cells that pump the dark pigment melanin

into our hair and skin

and give them colour.

lt'sjust the amount of melanin

these cells produce

that determines whether we are black or white,

brunette or blonde.

Generally speaking,

the more melanin, the darker.

That same chemical adds colour

to a very different sensory organ.

Blue or brown,

green or hazel,

they are the most vital sensory organ

that the incredible machine has.

Our day hasjust begun,

and the magnificent miracle of sight

leads the way.

Navigating the morning rush hour is something

most human machines do on autopilot,

oblivious to the staggering task

we leave to two gelatinous orbs.

Eyes sit squarely on the front of our faces

for a reason.

Peering forward, and set apartjust enough

to let us gauge distance,

they let us spot and track whatever we desire.

ln microseconds, our eyes sight, follow,

focus and process images

fractions of an inch long

or moving at hundreds of miles per hour

enabling us to assess and appreciate

the world around us more than any other sense.

They may be the windows to our souls,

but on a less poetic level,

eyes are just hungry harvesters of light,

trapping and translating it into

electrical impulses the brain can understand.

Light hits the cornea first.

This transparent layer, cleansed and lubricated

about 1 0 times a minute with every blink,

admits and directs incoming light rays.

From there, they pass through

the dark opening of the pupil,

then a transparent protein lens.

Gatekeepers of light, the muscles of

the colourful iris squeeze the pupil closed

against too much light.

Not enough, the iris relaxes

and the pupil opens.

And in just a fraction of a second,

it can slide back and forth between the two.

Focused by cornea and lens,

light then flies through the jelly-like bulk

of the eye and onto its rear wall.

Just about a hundredth of an inch thick,

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