Inside The Human Body (2011) s01e00 Episode Script
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This athlete is a champion of one of the world's most spectacular sports - bull jumping.
CHEERING AND APPLAUSE These fishermen can see underwater better than almost anyone else on Earth.
And this is the ice man.
He can thrive where his flesh should freeze.
Their stories are part of your story .
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the story of what makes you human.
You are the most fascinating creature ever to have drawn breath on this planet.
And the reason lies under your skin.
Hidden deep inside you is a wonderful dynamic world.
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where vast forests of cells capture light.
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where tiny movements trigger fierce electrical storms .
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and raging torrents of blood feed your brain.
This is a fantastic voyage through the most complex organism on Earth.
You.
Just existing for one minute feels like the simplest thing in the world.
Yet what goes on inside you every 60 seconds is wonderfully complicated.
If you stop and think about it, it is truly remarkable, the way that your body, every minute of every hour of every day, is doing a million different things to keep YOU alive.
And you're not even aware of it.
Your heart will beat 70 times, driving 5 litres of blood around the 96,000 kilometres of your circulation.
Deep inside your bone marrow, each minute, 150 million red blood cells will be born.
And while you're sitting there, the 250 square metres of your gut are busy digesting the meal you've just eaten.
What's really impressive is not just that our bodies do all these things all the time, but they respond instantly to any change in our environment.
Your brain is soaking up vital information from the world around you, Through your senses.
And your body is on constant alert to keep you safe and out of danger.
This film will show you how you do it.
We'll begin with the extraordinary sequence of events that led to your birth.
This is Diane.
She's experiencing a most improbable pregnancy.
DIANE: Right MAN: Ooh.
That's it.
Good.
CHUCKLES That's quite nice, actually.
Is it? If I do that, it stretches my legs more.
You've got to stay like that as long as you can.
I know.
Diane got pregnant three times and all at once.
She's carrying triplets.
If you can hold the back of my calves and then push my legs forward for me.
Unusually, Diane's body produced three eggs at the same time.
When it came to the end of the scan, she said, "Well, just before I show you the screen, "just to let you know there's more than one.
" So me and Mike said, "Oh, twins? That's lovely!" She went, "No, no, there's three.
" I even said to her, "Are you sure?" Yeah.
"Of course I'm sure, they're on the screen!" The prospect of three babies came as a big shock.
You burst out crying.
I started crying for about 30 seconds solidly, hysterical crying.
And then it turned to laughter, hysterical laughter.
Mike had his head in his hands.
Head in his hands! Like this.
It's incredibly rare for a multiple pregnancy like this one to happen naturally.
All three babies are growing inside Diane completely independently of each other.
Apparently, I released three eggs and Mike, he had three separate sperm that fertilised all three eggs.
They've all got their own placentas and they're all in separate sacs, so they've all got their own little bedroom.
CHUCKLES Producing three eggs in one go naturally, as Diane did, is extremely rare.
But getting pregnant at all is surprisingly complicated.
As many as 250 million sperm will start the journey into the woman's body but very few will make it to the egg.
Sperm are alien and the woman's immune system is triggered to kill them.
White blood cells attack the sperm from all directions.
By the time any survivors reach the safety of a Fallopian tube, of the original 250 million, there could be as few as 20 left.
It might seem odd, but it's actually an incredibly effective selection process.
And it clearly works because humans can be extremely successful breeders.
I'm Christi Cason and I'm 39, and I'm about to have a baby 14 months after my last one.
Christi's body had barely recovered from childbirth when she got pregnant again.
Are you nervous, excited about this one? DAVE: Yeah, I'm confident.
But, yeah, nervous too.
Christi has been getting pregnant almost yearly for the past 20 years.
We also have Laura - two, Morgan - three, Walker - five, Trevor - six, Rebekah - seven, Emma - eight, Harper - ten, Kaylee -11, Gage - 13, Bailey -14.
Oh, my gosh! Austin who's 16, Dalton - 18, Chad - 19, and Jessica who is 21.
This will be Christi's 16th baby.
She's spent the majority of her adult life pregnant.
If you tot it all up, Christi has been continuously pregnant for over 12 years.
And although she is now carrying their 16th child, she's already planning another.
I guess our family's just not complete yet.
In a little while, will I go, "I want to have another," you know? Do the whole experience again.
Christi, like all women, has only a limited supply of eggs.
A woman is born with all the eggs she will ever have.
It's a strange thought, but the egg that led to you started life inside your grandmother.
It's quite remarkable when you think about it, because what it means is that part of you started life before your mother was even born.
It's actually quite difficult to get your head round.
Now, this is a picture of me as a chubby one-year-old, and the egg that made me was inside my mother when she was just a foetus inside my grandmother back in 1928, which means that part of me, at least, is over 80 years old.
The precious egg that became you was stored inside your mother's ovaries for decades.
Then, when its time came, it rose to the surface and ripened.
As soon as an egg is ripe, it's released from the ovary .
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and gently wafted into the opening of the Fallopian tube.
The sperm are now in a race to the finish.
They have come a long way, but there can only be one winner.
The competing sperm break off the cloud of cells that surround the egg.
They struggle to burrow in until, finally, one pushes through the soft shell underneath.
This is a critical moment for the egg.
If a second sperm gets in, the egg won't survive.
It must quickly protect itself.
Under the shell, tiny granules detonate, hardening and making the egg impenetrable.
A new life is under way.
for the first few weeks, as you developed in the womb, you looked nothing like a human.
But by ten weeks, you had developed your face.
It tells the world what you're feeling, who you are and where you come from.
No two faces are exactly the same, which is part of their charm, but we do share a number of common features.
A couple of eyes, nose, mouth.
But there's also another feature, which has no obvious function.
We see it every day in the mirror, we probably never think about it, but this feature provides a vital clue as to how our faces first formed.
Down the centuries, biologists have wondered why every face has this particular feature.
It's this bit here, the groove underneath your nose.
It's called the "philtrum".
I've got quite a prominent one, his is less prominent, but we've all got one.
What we now know is it is the place where the puzzle that is the human face finally all comes together.
We've taken data from scans of a developing embryo so we are able to show you for the very first time how our faces don't just grow, but fit together like a puzzle.
The three main sections of the puzzle meet in the middle of your top lip, creating the groove that is your philtrum.
This whole amazing process, the bits coming together to produce a recognisable human face, happens in the womb between two and three months.
If it doesn't happen then, it never will.
Around the world, one in 700 babies are born with what are called "clefts".
Here in India, they are all too common.
Plastic surgeon Per Hall is a volunteer, part of an international medical team who've come to northeast India with the charity Operation Smile.
The team are here to put right where nature went wrong.
In the next ten days, they hope to perform 250 cleft operations.
Hello.
Hello, Majoni.
How are you? So, she's got a cleft palate that goes all the way through right to the back.
Eight-year-old Majoni has a cleft lip and palate.
This is a functional problem for speech and swallowing.
She'll be able to say "m" and "n" and maybe "g" sounds, but none of the sounds that you need your tongue to come forward or to stop air coming out of your nose, will she be able to make.
So, when she tries to talk, people will probably think she's a bit stupid.
But actually, she's not.
She's completely normal intelligence.
Clefts are so common because, for the sections of the face to fuse correctly, they must meet at precisely the right time in the womb.
For the palate, the time window is only a matter of hours.
It is absolutely extraordinary that this all happens in the womb some time between when we're the size of a grain of rice or the size of a small chilli bean.
Majoni has lived with her clefts for eight years.
Today is the first step towards a new life.
I can see the beauty there, despite the fact that perhaps others can't see that, because I know what she could look like.
To repair Majoni's face, Per is replicating what should have happened in the womb.
The next morning, Majoni can see her amazing transformation.
Have you seen your face? Do you want to have a look? Look! That's you.
Per has given her the prospect of a far better future.
Once your face had formed in the womb, you just went right on growing.
Your every need was taken care of by your mother.
You didn't have to eat for yourself .
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you didn't even have to breathe for yourself.
Your mother's blood supplied you with oxygen, so your own lungs weren't needed.
And because you didn't need your lungs, your body didn't bother sending blood to them, but shunted it through a hole in your heart instead.
Then, suddenly, you were on your own.
This is Tyriece.
He's just been born.
As he emerges into the world, his body must take over from his mother's.
The shock of cold air and bright lights triggers his first breath.
But before Tyriece can take in oxygen, his heart has to connect with his lungs.
And to do this, the hole in his heart has to close.
As you draw your first breath, the airways of your lungs open, and the drop in pressure causes blood to rush into them to pick up oxygen.
That oxygen-rich blood then flows to the heart for the very first time.
The pressure of this flood of blood pushes on a flap, closing the hole.
But sometimes it doesn't seal.
One in four of us has a hole in the heart, and most will never know.
Your heart and lungs are now fully connected.
Your circulation is complete.
Finally got my boy.
Got what I've always wanted.
Over the moon.
Yeah.
So you can take another breath and another.
From now on, without thinking, you will breathe around 16 times every minute.
You only really start thinking about breathing when you stop.
I'm going see how long I can hold my breath for, starting right now.
'Try it yourself.
' Oh! HE COUGHS Oh, that was not impressive.
That was40 seconds.
I reckon I could probably do about another 10 seconds.
It really hurt.
Sounder a minute.
Not impressive at all.
There are some people who can go a hell of a lot longer than that.
This man can hold his breath for a whopping nine minutes.
Herbert Nitsch is a world champion at freediving.
Because he doesn't rely on bulky breathing apparatus, he can glide through the water with the freedom of a fish.
The fish or mammals in the water come right into your face, look at you.
I'm like, "OK, that's maybe even closer than I would want to, maybe.
" But they're just curious, because they think that you are one of them.
Before a dive, Herbert takes in as much air as he can.
But, surprisingly, the key to success is not so much his lungs as his heart.
As Herbert plunges deep into the sea, the cold water on his face prompts something we all have - the dive reflex.
HEARTBEA This reflex causes your heartbeat to slow by as much as 25%, so you use less oxygen.
And the dive reflex does something more.
It priorities the brain and the heart's survival by switching off the more dispensable parts of the body.
After mere seconds, Herbert's body shuts off blood flow to his extremities.
First, his toes and fingers.
Then his hands and feet.
And, finally, his arms and legs until all that remains is a circuit of blood flowing between his heart and his brain.
And that is what allows him to stay underwater for an incredible nine minutes.
What this really shows is how good your heart is at adapting to any environment.
Your heart is an exquisitely engineered pump, made of muscle.
And you can see the true elegance of this engineering if you slow it to a single beat.
Inside the cavernous chambers, the muscles work together in perfect harmony.
These muscles never get tired and never stop working.
As your heart expands, blood flows from your body into its chambers.
Then an electrical signal storms through the heart, causing it to contract .
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forcing blood all the way through your body's vast network of vessels.
And to stop the blood flowing backwards, your heart needs valves.
As they slam shut, these valves make the familiar "lub-dub, lub-dub".
HEARTBEATS The soundtrack of your life.
That "lub dub" rhythm changes in step with your needs.
What I love about my heart is it is incredibly sensitive.
It responds immediately to any demands put upon it.
At the moment, it is rattling along at around 64 beats a minute.
Time to give it a bit of a work-out.
Right.
It has now gone up to 84.
Bit faster.
Up to 99.
Jog, jog, jog and now108.
Right, I'm going see how far I can push it, run up and down the stairs a few times.
My heart matches the workload in my muscles.
As they work harder, my heart responds by pushing more blood around my body, keeping my blood oxygen levels balanced.
Right, 120.
And now that I'm at rest, it's already beginning to drop.
That is a truly wonderful piece of machinery.
And what's driving all this machinery is the master control centre of your body - your brain.
It contains 100 billion brain cells, which control everything you do.
It's incredibly sophisticated, but it hasn't always been that way.
Hey! Hey, baby.
This is Phoebe.
She's three months old, and her brain is hopeless at pretty much everything.
It can tell her mouth to suck, but can't feed itself .
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can't maintain her body temperature .
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can't even control when she goes to the loo.
Before Phoebe can become more independent, her brain has to learn about the world she lives in.
Where's Mummy gone? Shall I come back? And the main way she does this is through her eyes.
At the back of the eye is the red plain of your retina.
Here, light from outside shines down, casting images across the surface.
Underneath, there's a dense forest of 125 million light-sensitive cells.
Each cell detects just a tiny part of any image.
They send these minute fragments of information to your brain, which has to put it all together.
In the first few years of your life, some of the cells begin to group together, causing the retina's surface to bulge.
As they continue to rise, they create a volcano-like structure.
It's not till you are four years old that the mound is finally finished.
This is your fovea.
It's the only part of your eye where your vision is crystal clear and it's capable of sensing millions of different colours.
Your eyes are actually an extension of your brain.
And they are so adaptable that you can learn to see in places where human eyes would normally struggle.
Underwater, the world looks blurry and indistinct.
As you descend, light levels drop rapidly.
Your eye reacts by opening the iris, making the pupil larger and allowing more light in.
The image becomes brighter, but underwater, a larger pupil also makes the image more blurred.
Goon and his friends are Moken sea gypsies from Thailand.
They've learnt how to see underwater more clearly by overruling this automatic reflex.
You can actually watch this happen with the help of an infrared camera.
Instead of opening his pupils, he closes them as far as they will go.
This means Goon can see twice as well underwater as you or I can.
Recent studies suggest that any child can quickly learn this trick.
The Moken show how well the human brain can adapt the body to suit its needs.
Now you might imagine that your brain's main job is thinking, but actually, one of the hardest jobs it does is control your balance and coordinate your movements.
This is such a complex task it involves as many brain cells as the whole of the rest of your brain put together.
Standing up feels easy, natural, but learning how to do so was hard - really hard.
Today, I want to try and recreate that challenge, that problem that we all had to face and overcome when we took our first steps.
That's it, good.
Right Keep your arms nice and high.
'Like all beginners, I need a helping hand' It's going to get wobbly.
Keep it going forwards.
'.
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not from my mother, but tight-line walker Alana Jones.
' First steps, it was all right.
But that's only because I was holding onto you.
And again, and again.
Keep control of those arms.
Keep going, keep walking.
Keep walking.
Keepwalking! Whoo! The thing about this is it's fantastically hard because you are using something like 54 different muscles in your leg but at the same time, you require at least 640 muscles of your body.
'And all of these muscles are being directed 'by a bizarre part of your inner ear.
' This cavern is buried deep inside your head.
It's part of a labyrinth of twisting tunnels completely submerged in fluid.
The tunnels are the three great loops of your semicircular canals.
Inside each loop there is a saddle-topped fleshy mountain - your crista.
The mountain slopes are covered in a thick forest of tiny hair cells.
For the moment, they lie still.
But this inner sea never remains calm for long.
ROARING, GURGLING LIQUID As your head moves, it generates a shock wave, which races through the tunnel and pummels the mountain.
On its flanks, the hair cells are thrown about in the turbulent waters.
The pressure builds until electricity flows.
This powerful electrical current then sends messages back to your brain .
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giving you your sixth sense - your sense of balance.
Take your back leg off.
Off, off, off.
Oh Oh Good.
And again, off.
Good.
And again.
Whoo! Yes! Your brain's ability to precisely control the 640 muscles of your body is absolutely essential when it comes to dodging danger.
In a form of bullfighting, known as recortes, the bulls are unharmed, but the men rely on their muscles to avoid a gruesome death.
They're not allowed to use weapons or armour.
Instead, they rely solely on speed and agility.
It's Cristian's turn to enter the ring.
He's a champion, and he takes some of the greatest risks - risks that, even with all his experience, he finds scary.
Escaping uninjured will depend on how his muscles respond in the next few moments.
We all have two different kinds of skeletal muscle fibres.
Just like a chicken, we have dark and white meat.
You use your dark, slow-twitch muscles for things like walking.
They work tirelessly for long periods of time, so they need a constant supply of oxygen-rich blood.
But you also have white, fast-twitch muscles, which rely on a rapid chemical reaction.
They can constrict four times faster than slow-twitch muscles and allow you to react quickly.
These are the muscles Cristian will use to try and leap over the bull.
APPLAUSE Whoever you are, and whatever you're doing, your body is constantly alert and working hard to keep you safe.
It's not all about honed muscles and fast reaction times.
You also have the largest organ in your body to fall back on.
That organ is, of course, your skin.
If you were to skin me alive and then spread it all out, then my skin would cover an area about the size and thickness of this beach towel.
And it's covered with receptors that are constantly monitoring the world .
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and feeding back information.
Whoo! HE GASPS This water is a very chilly ten degrees.
Ah! God, that is cold! Now, my skin is packed with sensors which warn me about danger.
And some of the sensors are telling me at the moment, the pain sensors, of which there are a few million, are screaming, "This is really cold, this is really unpleasant.
" Not damagingly unpleasant, so my brain is going, "Don't panic, it's all right," but unpleasant.
Phew! At the same time, my temperature receptors, which are also in the skin, are shouting, "This is cold, go faster, "try and warm up.
" But the temperature of this water is absolutely nothing compared to what one man can cope with.
These are the frozen wastes of Iceland .
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and this is Wim Hof, also known as "The Iceman".
Unbelievably, he's about to take a swim in this lake.
The water here is just above freezing, two degrees Celsius.
Wim intends to stay in for 15 minutes, which would kill most people.
But he's looking forward to it.
Water looks clear, good.
Inviting, attractive.
Powerful.
The first minute in ice-cold water is the most dangerous.
As your skin senses such intense cold, your body goes into shock, which can trigger a heart attack.
I don't feel the cold.
I feel the power, yes.
I don't feel the pain, because I am stronger than the pain at that moment.
Wim believes that everyone could do what he does.
It is trainable.
No hocus-pocus.
It's the mind.
There is a natural ability in everybody to neutralise the cold.
It's a privilege to be here.
Look at this.
Diamonds! Wim has survived 15 minutes in ice-cold water.
It's a real testimony to the body's amazing ability to adapt to almost unimaginable extremes.
Many animals, like reptiles, can't control their temperature at all.
They rely on sunshine to warm them up.
But we're different.
We can go where we want, when we want.
One of the reasons why we are such a successful species, in fact, why we dominate the planet, is because we keep our bodies at a really constant warm 37 degrees, no matter how extreme the external environment.
For these elite firefighters in Texas, their body's ability to keep cool is a matter of life and death.
And the way they do it is by sweating.
Sweating is a part of the game when it comes to firefighting.
I've seen guys actually pour sweat out of their boots.
They've taken their T-shirts and they wring the sweat out.
If I couldn't sweat, I couldn't go in and do what I need to do.
I couldn't be a firefighter.
When your body starts to overheat, it stimulates sweat glands deep down within your skin .
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to produce a tiny bead of sweat.
Each bead must then work its way to your skin's surface.
And it's here that sweat performs its magic.
As it evaporates into the air, it takes heat with it.
This is how your body maintains its cool .
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and keeps firemen alive when things heat up.
In this rescue simulation, the temperature is 1,200 degrees.
It's so intense that in the single minute that this firefighter is exposed to the fire he will lose three pounds in weight as sweat.
So, your skin keeps you alive by controlling your temperature.
But it also does something else which is just as crucial for your survival.
Each square centimetre of your skin has 10 million bacteria camped out on it.
The tissues inside your body would provide a nice, juicy home, if only they could get in.
What keeps them at bay is the way your skin cells lock together, just like armour plating.
And your skin is also constantly pushing outwards.
As new layers grow, the old surface layers peel away, carrying a cargo of unwanted microbes with them.
But this also means you lose 30,000 skin cells every minute.
By this time next month, you'll have replaced all the skin on your body.
Your skin is an absolutely fabulous barrier against infections, but unfortunately, it has great big holes in it.
I'm talking through one at the moment, I've got ears, and there are a few other orifices I don't even want to think about.
Oddly enough, it's holes that you probably don't even regard as holes that are particularly vulnerable.
They are your eyes.
Your eyes are one of the weak points that microbes use to get into your body.
Imagine someone has sneezed, and a few droplets have landed here on this tabletop.
I'm drumming my fingers, the viruses are on my fingertips, I now play around with my face a bit, and then, because I'm feeling a bit tired, I decide to rub my eyeballs, and THAT is when the viruses get in.
Viruses have found a way to use our own defence mechanism - sneezing - against us.
A sneeze is all it takes for microbes to jump from one person to another.
The main reason you sneeze is to clear your nose of dust and other fine particles.
But as you blast out air at up to 100mph, you also spray a fine mist of droplets containing millions of microbes .
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anything up to 12 feet away, giving the microbes the perfect opportunity to find a new host.
If they do get inside you, your body quickly responds by mobilising an army of white blood cells.
Now, if you want to see some of these ferocious little fighters in action, all you have to do is prick your finger.
Ooh In a tiny drop of blood like this one here, there are around 400,000 white cells.
These are my white blood cells up here on the screen.
They're called phagocytes, because they eat things.
And these little green blobs are fake bacteria.
It may look like a cheap computer game, but what you're seeing in action is one of the most sophisticated defence systems on the planet.
And there's one here that's just begun to attack.
What's it going to do? It's sort of sniffing around.
It's obviously grabbed this bacteria.
Having a bit of a wrestling match.
And there it goes, it's swallowed it.
It is absolutely astonishing that this is all going on inside me at this very moment.
I don't have to think about it, it just does it.
Right or left? Do you know that letter? Yes.
Rowan O'Brien is three years old.
He should be at school, but he's feeling unwell.
What letter's that one? Muh! That's it.
That's it.
He's got the flu.
No, that's not right.
No.
1, 2, 3, 4, 5 Inside him, his body is about to engage in all-out war with one of the most infectious viruses on the planet.
Flu viruses start by attacking the tissue at the back of your throat.
But strangely enough, it's not only the virus that will make you feel ill, it's also your own immune system.
Your body's first response to infection is fever.
The flu virus thrives at your normal body temperature of 37 degrees Celsius .
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so you raise your temperature by a few degrees.
It's just enough to slow the infection down.
Meanwhile, an army of phagocytes flood the infection site.
They have come to feast on their enemies.
But instead of destroying the viruses, the fighters are themselves infected and are forced to self-destruct.
HE SNEEZES As their bodies pile up, they form the basis of your snot.
Rowan's symptoms are getting worse.
You're a little bit hot.
It's a sign the battle inside him is hotting up.
His body has launched a second wave of attack - the killer Ts.
They home in on the throat cells that have been infected by the virus.
They administer the kiss of death, destroying the viruses inside.
But this approach has its cost.
The killer Ts are causing heavy collateral damage.
HE COUGHS Rowan is feeling the effects.
HE COUGHS He's got a really sore throat.
Despite everything, the virus remains undefeated.
Now your immune system tries a completely different approach.
Instead of trying to destroy the virus head-on, it releases a cloud of Y-shaped antibodies.
These are specifically produced to destroy this strain of virus.
They coat the viruses, making them stick together.
Now they are easily swept up.
Rowan finally starts to feel better.
And with his energy restored, he can go back to doing what three-year-old boys do best.
HE GIGGLES He's experienced an everyday miracle He's fought off an infection.
Whee! We are, each and every one of us, biological marvels, able to adapt to a challenging world.
Although we have our differences, we are fundamentally all the same.
CHILDREN LAUGH We smile using the same facial muscles.
We all stare out and see the world using the same eyes.
We have the same hearts .
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which work around the clock to keep us alive, tirelessly pumping blood, picking up oxygen from our lungs, and transporting it to every cell in our body.
We have such remarkable life-support systems, but at one level, all we really need is a bit of water, and a small bite of food.
And that nourishment feeds the most complex brains that have ever existed.
Each of our brains has 100 billion cells that are constantly processing a mass of information rushing in through our senses.
We all began the same way - when a precious egg and a single sperm came together, creating a new individual - you.
As our hearts began to beat, we grew from a tiny embryo .
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into the 100 trillion cells that make up every one of us.
'What our bodies can do is truly astonishing, 'but we are also so much more than the sum of our parts.
' We are impressive in our own right, but it's when we all get together that we're capable of truly remarkable things.
That right? ALL: Yeah!
CHEERING AND APPLAUSE These fishermen can see underwater better than almost anyone else on Earth.
And this is the ice man.
He can thrive where his flesh should freeze.
Their stories are part of your story .
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the story of what makes you human.
You are the most fascinating creature ever to have drawn breath on this planet.
And the reason lies under your skin.
Hidden deep inside you is a wonderful dynamic world.
.
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where vast forests of cells capture light.
.
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where tiny movements trigger fierce electrical storms .
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and raging torrents of blood feed your brain.
This is a fantastic voyage through the most complex organism on Earth.
You.
Just existing for one minute feels like the simplest thing in the world.
Yet what goes on inside you every 60 seconds is wonderfully complicated.
If you stop and think about it, it is truly remarkable, the way that your body, every minute of every hour of every day, is doing a million different things to keep YOU alive.
And you're not even aware of it.
Your heart will beat 70 times, driving 5 litres of blood around the 96,000 kilometres of your circulation.
Deep inside your bone marrow, each minute, 150 million red blood cells will be born.
And while you're sitting there, the 250 square metres of your gut are busy digesting the meal you've just eaten.
What's really impressive is not just that our bodies do all these things all the time, but they respond instantly to any change in our environment.
Your brain is soaking up vital information from the world around you, Through your senses.
And your body is on constant alert to keep you safe and out of danger.
This film will show you how you do it.
We'll begin with the extraordinary sequence of events that led to your birth.
This is Diane.
She's experiencing a most improbable pregnancy.
DIANE: Right MAN: Ooh.
That's it.
Good.
CHUCKLES That's quite nice, actually.
Is it? If I do that, it stretches my legs more.
You've got to stay like that as long as you can.
I know.
Diane got pregnant three times and all at once.
She's carrying triplets.
If you can hold the back of my calves and then push my legs forward for me.
Unusually, Diane's body produced three eggs at the same time.
When it came to the end of the scan, she said, "Well, just before I show you the screen, "just to let you know there's more than one.
" So me and Mike said, "Oh, twins? That's lovely!" She went, "No, no, there's three.
" I even said to her, "Are you sure?" Yeah.
"Of course I'm sure, they're on the screen!" The prospect of three babies came as a big shock.
You burst out crying.
I started crying for about 30 seconds solidly, hysterical crying.
And then it turned to laughter, hysterical laughter.
Mike had his head in his hands.
Head in his hands! Like this.
It's incredibly rare for a multiple pregnancy like this one to happen naturally.
All three babies are growing inside Diane completely independently of each other.
Apparently, I released three eggs and Mike, he had three separate sperm that fertilised all three eggs.
They've all got their own placentas and they're all in separate sacs, so they've all got their own little bedroom.
CHUCKLES Producing three eggs in one go naturally, as Diane did, is extremely rare.
But getting pregnant at all is surprisingly complicated.
As many as 250 million sperm will start the journey into the woman's body but very few will make it to the egg.
Sperm are alien and the woman's immune system is triggered to kill them.
White blood cells attack the sperm from all directions.
By the time any survivors reach the safety of a Fallopian tube, of the original 250 million, there could be as few as 20 left.
It might seem odd, but it's actually an incredibly effective selection process.
And it clearly works because humans can be extremely successful breeders.
I'm Christi Cason and I'm 39, and I'm about to have a baby 14 months after my last one.
Christi's body had barely recovered from childbirth when she got pregnant again.
Are you nervous, excited about this one? DAVE: Yeah, I'm confident.
But, yeah, nervous too.
Christi has been getting pregnant almost yearly for the past 20 years.
We also have Laura - two, Morgan - three, Walker - five, Trevor - six, Rebekah - seven, Emma - eight, Harper - ten, Kaylee -11, Gage - 13, Bailey -14.
Oh, my gosh! Austin who's 16, Dalton - 18, Chad - 19, and Jessica who is 21.
This will be Christi's 16th baby.
She's spent the majority of her adult life pregnant.
If you tot it all up, Christi has been continuously pregnant for over 12 years.
And although she is now carrying their 16th child, she's already planning another.
I guess our family's just not complete yet.
In a little while, will I go, "I want to have another," you know? Do the whole experience again.
Christi, like all women, has only a limited supply of eggs.
A woman is born with all the eggs she will ever have.
It's a strange thought, but the egg that led to you started life inside your grandmother.
It's quite remarkable when you think about it, because what it means is that part of you started life before your mother was even born.
It's actually quite difficult to get your head round.
Now, this is a picture of me as a chubby one-year-old, and the egg that made me was inside my mother when she was just a foetus inside my grandmother back in 1928, which means that part of me, at least, is over 80 years old.
The precious egg that became you was stored inside your mother's ovaries for decades.
Then, when its time came, it rose to the surface and ripened.
As soon as an egg is ripe, it's released from the ovary .
.
and gently wafted into the opening of the Fallopian tube.
The sperm are now in a race to the finish.
They have come a long way, but there can only be one winner.
The competing sperm break off the cloud of cells that surround the egg.
They struggle to burrow in until, finally, one pushes through the soft shell underneath.
This is a critical moment for the egg.
If a second sperm gets in, the egg won't survive.
It must quickly protect itself.
Under the shell, tiny granules detonate, hardening and making the egg impenetrable.
A new life is under way.
for the first few weeks, as you developed in the womb, you looked nothing like a human.
But by ten weeks, you had developed your face.
It tells the world what you're feeling, who you are and where you come from.
No two faces are exactly the same, which is part of their charm, but we do share a number of common features.
A couple of eyes, nose, mouth.
But there's also another feature, which has no obvious function.
We see it every day in the mirror, we probably never think about it, but this feature provides a vital clue as to how our faces first formed.
Down the centuries, biologists have wondered why every face has this particular feature.
It's this bit here, the groove underneath your nose.
It's called the "philtrum".
I've got quite a prominent one, his is less prominent, but we've all got one.
What we now know is it is the place where the puzzle that is the human face finally all comes together.
We've taken data from scans of a developing embryo so we are able to show you for the very first time how our faces don't just grow, but fit together like a puzzle.
The three main sections of the puzzle meet in the middle of your top lip, creating the groove that is your philtrum.
This whole amazing process, the bits coming together to produce a recognisable human face, happens in the womb between two and three months.
If it doesn't happen then, it never will.
Around the world, one in 700 babies are born with what are called "clefts".
Here in India, they are all too common.
Plastic surgeon Per Hall is a volunteer, part of an international medical team who've come to northeast India with the charity Operation Smile.
The team are here to put right where nature went wrong.
In the next ten days, they hope to perform 250 cleft operations.
Hello.
Hello, Majoni.
How are you? So, she's got a cleft palate that goes all the way through right to the back.
Eight-year-old Majoni has a cleft lip and palate.
This is a functional problem for speech and swallowing.
She'll be able to say "m" and "n" and maybe "g" sounds, but none of the sounds that you need your tongue to come forward or to stop air coming out of your nose, will she be able to make.
So, when she tries to talk, people will probably think she's a bit stupid.
But actually, she's not.
She's completely normal intelligence.
Clefts are so common because, for the sections of the face to fuse correctly, they must meet at precisely the right time in the womb.
For the palate, the time window is only a matter of hours.
It is absolutely extraordinary that this all happens in the womb some time between when we're the size of a grain of rice or the size of a small chilli bean.
Majoni has lived with her clefts for eight years.
Today is the first step towards a new life.
I can see the beauty there, despite the fact that perhaps others can't see that, because I know what she could look like.
To repair Majoni's face, Per is replicating what should have happened in the womb.
The next morning, Majoni can see her amazing transformation.
Have you seen your face? Do you want to have a look? Look! That's you.
Per has given her the prospect of a far better future.
Once your face had formed in the womb, you just went right on growing.
Your every need was taken care of by your mother.
You didn't have to eat for yourself .
.
you didn't even have to breathe for yourself.
Your mother's blood supplied you with oxygen, so your own lungs weren't needed.
And because you didn't need your lungs, your body didn't bother sending blood to them, but shunted it through a hole in your heart instead.
Then, suddenly, you were on your own.
This is Tyriece.
He's just been born.
As he emerges into the world, his body must take over from his mother's.
The shock of cold air and bright lights triggers his first breath.
But before Tyriece can take in oxygen, his heart has to connect with his lungs.
And to do this, the hole in his heart has to close.
As you draw your first breath, the airways of your lungs open, and the drop in pressure causes blood to rush into them to pick up oxygen.
That oxygen-rich blood then flows to the heart for the very first time.
The pressure of this flood of blood pushes on a flap, closing the hole.
But sometimes it doesn't seal.
One in four of us has a hole in the heart, and most will never know.
Your heart and lungs are now fully connected.
Your circulation is complete.
Finally got my boy.
Got what I've always wanted.
Over the moon.
Yeah.
So you can take another breath and another.
From now on, without thinking, you will breathe around 16 times every minute.
You only really start thinking about breathing when you stop.
I'm going see how long I can hold my breath for, starting right now.
'Try it yourself.
' Oh! HE COUGHS Oh, that was not impressive.
That was40 seconds.
I reckon I could probably do about another 10 seconds.
It really hurt.
Sounder a minute.
Not impressive at all.
There are some people who can go a hell of a lot longer than that.
This man can hold his breath for a whopping nine minutes.
Herbert Nitsch is a world champion at freediving.
Because he doesn't rely on bulky breathing apparatus, he can glide through the water with the freedom of a fish.
The fish or mammals in the water come right into your face, look at you.
I'm like, "OK, that's maybe even closer than I would want to, maybe.
" But they're just curious, because they think that you are one of them.
Before a dive, Herbert takes in as much air as he can.
But, surprisingly, the key to success is not so much his lungs as his heart.
As Herbert plunges deep into the sea, the cold water on his face prompts something we all have - the dive reflex.
HEARTBEA This reflex causes your heartbeat to slow by as much as 25%, so you use less oxygen.
And the dive reflex does something more.
It priorities the brain and the heart's survival by switching off the more dispensable parts of the body.
After mere seconds, Herbert's body shuts off blood flow to his extremities.
First, his toes and fingers.
Then his hands and feet.
And, finally, his arms and legs until all that remains is a circuit of blood flowing between his heart and his brain.
And that is what allows him to stay underwater for an incredible nine minutes.
What this really shows is how good your heart is at adapting to any environment.
Your heart is an exquisitely engineered pump, made of muscle.
And you can see the true elegance of this engineering if you slow it to a single beat.
Inside the cavernous chambers, the muscles work together in perfect harmony.
These muscles never get tired and never stop working.
As your heart expands, blood flows from your body into its chambers.
Then an electrical signal storms through the heart, causing it to contract .
.
forcing blood all the way through your body's vast network of vessels.
And to stop the blood flowing backwards, your heart needs valves.
As they slam shut, these valves make the familiar "lub-dub, lub-dub".
HEARTBEATS The soundtrack of your life.
That "lub dub" rhythm changes in step with your needs.
What I love about my heart is it is incredibly sensitive.
It responds immediately to any demands put upon it.
At the moment, it is rattling along at around 64 beats a minute.
Time to give it a bit of a work-out.
Right.
It has now gone up to 84.
Bit faster.
Up to 99.
Jog, jog, jog and now108.
Right, I'm going see how far I can push it, run up and down the stairs a few times.
My heart matches the workload in my muscles.
As they work harder, my heart responds by pushing more blood around my body, keeping my blood oxygen levels balanced.
Right, 120.
And now that I'm at rest, it's already beginning to drop.
That is a truly wonderful piece of machinery.
And what's driving all this machinery is the master control centre of your body - your brain.
It contains 100 billion brain cells, which control everything you do.
It's incredibly sophisticated, but it hasn't always been that way.
Hey! Hey, baby.
This is Phoebe.
She's three months old, and her brain is hopeless at pretty much everything.
It can tell her mouth to suck, but can't feed itself .
.
can't maintain her body temperature .
.
can't even control when she goes to the loo.
Before Phoebe can become more independent, her brain has to learn about the world she lives in.
Where's Mummy gone? Shall I come back? And the main way she does this is through her eyes.
At the back of the eye is the red plain of your retina.
Here, light from outside shines down, casting images across the surface.
Underneath, there's a dense forest of 125 million light-sensitive cells.
Each cell detects just a tiny part of any image.
They send these minute fragments of information to your brain, which has to put it all together.
In the first few years of your life, some of the cells begin to group together, causing the retina's surface to bulge.
As they continue to rise, they create a volcano-like structure.
It's not till you are four years old that the mound is finally finished.
This is your fovea.
It's the only part of your eye where your vision is crystal clear and it's capable of sensing millions of different colours.
Your eyes are actually an extension of your brain.
And they are so adaptable that you can learn to see in places where human eyes would normally struggle.
Underwater, the world looks blurry and indistinct.
As you descend, light levels drop rapidly.
Your eye reacts by opening the iris, making the pupil larger and allowing more light in.
The image becomes brighter, but underwater, a larger pupil also makes the image more blurred.
Goon and his friends are Moken sea gypsies from Thailand.
They've learnt how to see underwater more clearly by overruling this automatic reflex.
You can actually watch this happen with the help of an infrared camera.
Instead of opening his pupils, he closes them as far as they will go.
This means Goon can see twice as well underwater as you or I can.
Recent studies suggest that any child can quickly learn this trick.
The Moken show how well the human brain can adapt the body to suit its needs.
Now you might imagine that your brain's main job is thinking, but actually, one of the hardest jobs it does is control your balance and coordinate your movements.
This is such a complex task it involves as many brain cells as the whole of the rest of your brain put together.
Standing up feels easy, natural, but learning how to do so was hard - really hard.
Today, I want to try and recreate that challenge, that problem that we all had to face and overcome when we took our first steps.
That's it, good.
Right Keep your arms nice and high.
'Like all beginners, I need a helping hand' It's going to get wobbly.
Keep it going forwards.
'.
.
not from my mother, but tight-line walker Alana Jones.
' First steps, it was all right.
But that's only because I was holding onto you.
And again, and again.
Keep control of those arms.
Keep going, keep walking.
Keep walking.
Keepwalking! Whoo! The thing about this is it's fantastically hard because you are using something like 54 different muscles in your leg but at the same time, you require at least 640 muscles of your body.
'And all of these muscles are being directed 'by a bizarre part of your inner ear.
' This cavern is buried deep inside your head.
It's part of a labyrinth of twisting tunnels completely submerged in fluid.
The tunnels are the three great loops of your semicircular canals.
Inside each loop there is a saddle-topped fleshy mountain - your crista.
The mountain slopes are covered in a thick forest of tiny hair cells.
For the moment, they lie still.
But this inner sea never remains calm for long.
ROARING, GURGLING LIQUID As your head moves, it generates a shock wave, which races through the tunnel and pummels the mountain.
On its flanks, the hair cells are thrown about in the turbulent waters.
The pressure builds until electricity flows.
This powerful electrical current then sends messages back to your brain .
.
giving you your sixth sense - your sense of balance.
Take your back leg off.
Off, off, off.
Oh Oh Good.
And again, off.
Good.
And again.
Whoo! Yes! Your brain's ability to precisely control the 640 muscles of your body is absolutely essential when it comes to dodging danger.
In a form of bullfighting, known as recortes, the bulls are unharmed, but the men rely on their muscles to avoid a gruesome death.
They're not allowed to use weapons or armour.
Instead, they rely solely on speed and agility.
It's Cristian's turn to enter the ring.
He's a champion, and he takes some of the greatest risks - risks that, even with all his experience, he finds scary.
Escaping uninjured will depend on how his muscles respond in the next few moments.
We all have two different kinds of skeletal muscle fibres.
Just like a chicken, we have dark and white meat.
You use your dark, slow-twitch muscles for things like walking.
They work tirelessly for long periods of time, so they need a constant supply of oxygen-rich blood.
But you also have white, fast-twitch muscles, which rely on a rapid chemical reaction.
They can constrict four times faster than slow-twitch muscles and allow you to react quickly.
These are the muscles Cristian will use to try and leap over the bull.
APPLAUSE Whoever you are, and whatever you're doing, your body is constantly alert and working hard to keep you safe.
It's not all about honed muscles and fast reaction times.
You also have the largest organ in your body to fall back on.
That organ is, of course, your skin.
If you were to skin me alive and then spread it all out, then my skin would cover an area about the size and thickness of this beach towel.
And it's covered with receptors that are constantly monitoring the world .
.
and feeding back information.
Whoo! HE GASPS This water is a very chilly ten degrees.
Ah! God, that is cold! Now, my skin is packed with sensors which warn me about danger.
And some of the sensors are telling me at the moment, the pain sensors, of which there are a few million, are screaming, "This is really cold, this is really unpleasant.
" Not damagingly unpleasant, so my brain is going, "Don't panic, it's all right," but unpleasant.
Phew! At the same time, my temperature receptors, which are also in the skin, are shouting, "This is cold, go faster, "try and warm up.
" But the temperature of this water is absolutely nothing compared to what one man can cope with.
These are the frozen wastes of Iceland .
.
and this is Wim Hof, also known as "The Iceman".
Unbelievably, he's about to take a swim in this lake.
The water here is just above freezing, two degrees Celsius.
Wim intends to stay in for 15 minutes, which would kill most people.
But he's looking forward to it.
Water looks clear, good.
Inviting, attractive.
Powerful.
The first minute in ice-cold water is the most dangerous.
As your skin senses such intense cold, your body goes into shock, which can trigger a heart attack.
I don't feel the cold.
I feel the power, yes.
I don't feel the pain, because I am stronger than the pain at that moment.
Wim believes that everyone could do what he does.
It is trainable.
No hocus-pocus.
It's the mind.
There is a natural ability in everybody to neutralise the cold.
It's a privilege to be here.
Look at this.
Diamonds! Wim has survived 15 minutes in ice-cold water.
It's a real testimony to the body's amazing ability to adapt to almost unimaginable extremes.
Many animals, like reptiles, can't control their temperature at all.
They rely on sunshine to warm them up.
But we're different.
We can go where we want, when we want.
One of the reasons why we are such a successful species, in fact, why we dominate the planet, is because we keep our bodies at a really constant warm 37 degrees, no matter how extreme the external environment.
For these elite firefighters in Texas, their body's ability to keep cool is a matter of life and death.
And the way they do it is by sweating.
Sweating is a part of the game when it comes to firefighting.
I've seen guys actually pour sweat out of their boots.
They've taken their T-shirts and they wring the sweat out.
If I couldn't sweat, I couldn't go in and do what I need to do.
I couldn't be a firefighter.
When your body starts to overheat, it stimulates sweat glands deep down within your skin .
.
to produce a tiny bead of sweat.
Each bead must then work its way to your skin's surface.
And it's here that sweat performs its magic.
As it evaporates into the air, it takes heat with it.
This is how your body maintains its cool .
.
and keeps firemen alive when things heat up.
In this rescue simulation, the temperature is 1,200 degrees.
It's so intense that in the single minute that this firefighter is exposed to the fire he will lose three pounds in weight as sweat.
So, your skin keeps you alive by controlling your temperature.
But it also does something else which is just as crucial for your survival.
Each square centimetre of your skin has 10 million bacteria camped out on it.
The tissues inside your body would provide a nice, juicy home, if only they could get in.
What keeps them at bay is the way your skin cells lock together, just like armour plating.
And your skin is also constantly pushing outwards.
As new layers grow, the old surface layers peel away, carrying a cargo of unwanted microbes with them.
But this also means you lose 30,000 skin cells every minute.
By this time next month, you'll have replaced all the skin on your body.
Your skin is an absolutely fabulous barrier against infections, but unfortunately, it has great big holes in it.
I'm talking through one at the moment, I've got ears, and there are a few other orifices I don't even want to think about.
Oddly enough, it's holes that you probably don't even regard as holes that are particularly vulnerable.
They are your eyes.
Your eyes are one of the weak points that microbes use to get into your body.
Imagine someone has sneezed, and a few droplets have landed here on this tabletop.
I'm drumming my fingers, the viruses are on my fingertips, I now play around with my face a bit, and then, because I'm feeling a bit tired, I decide to rub my eyeballs, and THAT is when the viruses get in.
Viruses have found a way to use our own defence mechanism - sneezing - against us.
A sneeze is all it takes for microbes to jump from one person to another.
The main reason you sneeze is to clear your nose of dust and other fine particles.
But as you blast out air at up to 100mph, you also spray a fine mist of droplets containing millions of microbes .
.
anything up to 12 feet away, giving the microbes the perfect opportunity to find a new host.
If they do get inside you, your body quickly responds by mobilising an army of white blood cells.
Now, if you want to see some of these ferocious little fighters in action, all you have to do is prick your finger.
Ooh In a tiny drop of blood like this one here, there are around 400,000 white cells.
These are my white blood cells up here on the screen.
They're called phagocytes, because they eat things.
And these little green blobs are fake bacteria.
It may look like a cheap computer game, but what you're seeing in action is one of the most sophisticated defence systems on the planet.
And there's one here that's just begun to attack.
What's it going to do? It's sort of sniffing around.
It's obviously grabbed this bacteria.
Having a bit of a wrestling match.
And there it goes, it's swallowed it.
It is absolutely astonishing that this is all going on inside me at this very moment.
I don't have to think about it, it just does it.
Right or left? Do you know that letter? Yes.
Rowan O'Brien is three years old.
He should be at school, but he's feeling unwell.
What letter's that one? Muh! That's it.
That's it.
He's got the flu.
No, that's not right.
No.
1, 2, 3, 4, 5 Inside him, his body is about to engage in all-out war with one of the most infectious viruses on the planet.
Flu viruses start by attacking the tissue at the back of your throat.
But strangely enough, it's not only the virus that will make you feel ill, it's also your own immune system.
Your body's first response to infection is fever.
The flu virus thrives at your normal body temperature of 37 degrees Celsius .
.
so you raise your temperature by a few degrees.
It's just enough to slow the infection down.
Meanwhile, an army of phagocytes flood the infection site.
They have come to feast on their enemies.
But instead of destroying the viruses, the fighters are themselves infected and are forced to self-destruct.
HE SNEEZES As their bodies pile up, they form the basis of your snot.
Rowan's symptoms are getting worse.
You're a little bit hot.
It's a sign the battle inside him is hotting up.
His body has launched a second wave of attack - the killer Ts.
They home in on the throat cells that have been infected by the virus.
They administer the kiss of death, destroying the viruses inside.
But this approach has its cost.
The killer Ts are causing heavy collateral damage.
HE COUGHS Rowan is feeling the effects.
HE COUGHS He's got a really sore throat.
Despite everything, the virus remains undefeated.
Now your immune system tries a completely different approach.
Instead of trying to destroy the virus head-on, it releases a cloud of Y-shaped antibodies.
These are specifically produced to destroy this strain of virus.
They coat the viruses, making them stick together.
Now they are easily swept up.
Rowan finally starts to feel better.
And with his energy restored, he can go back to doing what three-year-old boys do best.
HE GIGGLES He's experienced an everyday miracle He's fought off an infection.
Whee! We are, each and every one of us, biological marvels, able to adapt to a challenging world.
Although we have our differences, we are fundamentally all the same.
CHILDREN LAUGH We smile using the same facial muscles.
We all stare out and see the world using the same eyes.
We have the same hearts .
.
which work around the clock to keep us alive, tirelessly pumping blood, picking up oxygen from our lungs, and transporting it to every cell in our body.
We have such remarkable life-support systems, but at one level, all we really need is a bit of water, and a small bite of food.
And that nourishment feeds the most complex brains that have ever existed.
Each of our brains has 100 billion cells that are constantly processing a mass of information rushing in through our senses.
We all began the same way - when a precious egg and a single sperm came together, creating a new individual - you.
As our hearts began to beat, we grew from a tiny embryo .
.
into the 100 trillion cells that make up every one of us.
'What our bodies can do is truly astonishing, 'but we are also so much more than the sum of our parts.
' We are impressive in our own right, but it's when we all get together that we're capable of truly remarkable things.
That right? ALL: Yeah!