Browse content similar to Inside the Human Body - Learning Zone. Check below for episodes and series from the same categories and more!
Line | From | To | |
---|---|---|---|
You're a member of the most fascinating species on this planet. | 0:00:03 | 0:00:09 | |
And the secret lies under your skin. | 0:00:09 | 0:00:11 | |
This is a voyage through the most extraordinary organism on Earth. | 0:00:13 | 0:00:18 | |
You. | 0:00:21 | 0:00:23 | |
Your eye is a massive construction project. | 0:00:35 | 0:00:39 | |
And much of the development only begins after you are born. | 0:00:39 | 0:00:43 | |
The iris, which controls the amount of light entering your eye is complete, | 0:00:46 | 0:00:52 | |
but the muscles around the lens in the middle are still learning how to focus on the world. | 0:00:52 | 0:00:58 | |
At the back of your eye | 0:01:00 | 0:01:03 | |
lies the vast red plane of your retina. | 0:01:03 | 0:01:10 | |
Light from above shines down, casting images of the outside world across its surface. | 0:01:10 | 0:01:16 | |
Underneath, these rays enter a forest of 125 million light sensitive cells. | 0:01:20 | 0:01:28 | |
Each cell senses just a tiny part of the image but together | 0:01:30 | 0:01:35 | |
they send their information to the brain, which makes sense of it all. | 0:01:35 | 0:01:40 | |
Most of these are rod cells which can only see in shades of blue. | 0:01:40 | 0:01:45 | |
They help you see in the dark. | 0:01:46 | 0:01:49 | |
To see clearly in daylight you need an entirely different set of cells. | 0:01:53 | 0:01:58 | |
These are known as cone cells. | 0:02:02 | 0:02:05 | |
Four and a half million are spread over your retina. | 0:02:05 | 0:02:09 | |
But in one location, they are much denser. | 0:02:09 | 0:02:12 | |
Here, they begin to group together and the retina's surface begins to bulge. | 0:02:14 | 0:02:20 | |
Over the first four years of your life, the cones raise a volcano-like mound at the back of your eye. | 0:02:24 | 0:02:31 | |
Then, around 20,000 cone cells burst through at the summit. | 0:02:33 | 0:02:38 | |
This is your fovea. | 0:02:41 | 0:02:44 | |
The part of your eye where your vision is crystal clear. | 0:02:44 | 0:02:48 | |
It can sense over a million different colours. | 0:02:48 | 0:02:51 | |
Muscles in your eye work to focus light onto the retina. | 0:02:56 | 0:03:01 | |
Muscles in the iris respond to light levels, opening up | 0:03:03 | 0:03:07 | |
the iris in low light, and narrowing it when things get too bright. | 0:03:07 | 0:03:12 | |
On the remote Thai island of Ko Surin, | 0:03:18 | 0:03:21 | |
there are a group of people whose brains have learnt to overrule the muscles in their eyes. | 0:03:21 | 0:03:27 | |
Goong and his friends belong to the Moken tribe get much of their food from the sea. | 0:03:29 | 0:03:36 | |
But finding food in water is not easy. | 0:03:36 | 0:03:40 | |
That's because your eyes have adapted to see clearly in air, | 0:03:40 | 0:03:44 | |
so underwater they lose more than two-thirds of their power to see. | 0:03:48 | 0:03:53 | |
To compensate, Goong's brain does something remarkable. | 0:03:56 | 0:04:01 | |
As he descends, light levels drop quickly. | 0:04:01 | 0:04:06 | |
Normally, your eye would react | 0:04:08 | 0:04:10 | |
by opening the iris, making the pupil larger and allowing more light in. | 0:04:10 | 0:04:18 | |
The image may appear brighter, but it comes at a cost. | 0:04:18 | 0:04:23 | |
Because underwater, a wider iris makes everything appear more blurred. | 0:04:23 | 0:04:28 | |
Over time, Goong's brain has learned | 0:04:30 | 0:04:34 | |
to overrule this reflex of the eye...with an astonishing adaptation | 0:04:34 | 0:04:40 | |
best seen with the help of an infra-red camera. | 0:04:40 | 0:04:44 | |
Rather than opening his pupils, he closes them - | 0:04:44 | 0:04:48 | |
some of the muscles of the iris contract to their limit. | 0:04:48 | 0:04:52 | |
Which constricts the pupil as far as it will go. | 0:04:52 | 0:04:56 | |
Goong's view of the salty underwater world becomes much sharper. | 0:05:01 | 0:05:06 | |
It's so effective that Goong can see fine details twice as well as you can. | 0:05:12 | 0:05:20 | |
Your brain has an incredible ability to adapt your eyes to suit its needs. | 0:05:20 | 0:05:26 | |
And, for Goong, that means his dinner. | 0:05:26 | 0:05:30 | |
It is the incredible flexibility of the human brain | 0:05:42 | 0:05:45 | |
which enables you to respond to almost anything that happens to you. | 0:05:45 | 0:05:52 | |
But what you think you're seeing is really what your brain is interpreting. | 0:05:52 | 0:05:58 | |
It's an image that your brain constructs from the nerve impulses | 0:05:58 | 0:06:03 | |
it gets when light hits receptors in the retina. | 0:06:03 | 0:06:06 | |
Your brain makes sense of those signals and assembles a picture of the world around you. | 0:06:08 | 0:06:14 | |
The actual picture on your retina is upside down, | 0:06:16 | 0:06:20 | |
but your brain is clever enough to turn this the right way up. | 0:06:20 | 0:06:25 | |
One man's brain has done something even more spectacular. | 0:06:25 | 0:06:30 | |
I started going blind about ten years old. | 0:06:30 | 0:06:34 | |
Erik Weihenmayer's brain is 40 years old. | 0:06:37 | 0:06:41 | |
It lost contact with the visual world 25 years ago. | 0:06:43 | 0:06:47 | |
Every week I would wake up with different levels of vision. | 0:06:50 | 0:06:54 | |
Because my retinas were splitting away from my eyes. | 0:06:54 | 0:06:58 | |
And over a matter of four or five years I was totally blind. | 0:06:58 | 0:07:03 | |
Ever since, his brain has got used to being in the dark. | 0:07:05 | 0:07:10 | |
Today, Erik and his co-climber, Greg Childs, are in Utah. | 0:07:14 | 0:07:20 | |
They're about to attempt the formidable Castleton Rock. | 0:07:20 | 0:07:25 | |
It's a hard technical climb. | 0:07:32 | 0:07:34 | |
It's Erik's first attempt to climb here | 0:07:36 | 0:07:39 | |
and his brain is about to regain a sense of sight... | 0:07:39 | 0:07:43 | |
with a new piece of technology. | 0:07:43 | 0:07:46 | |
This is the brain port device. | 0:07:46 | 0:07:49 | |
This is the camera... | 0:07:49 | 0:07:53 | |
on these sunglasses here. | 0:07:53 | 0:07:55 | |
The camera sends a feed to a computer on Erik's hip... | 0:07:55 | 0:07:59 | |
..Which translates the images into a low-resolution picture of the world. | 0:08:02 | 0:08:06 | |
This blocky image is then sent to one of the most sensitive parts of Erik's body...his tongue. | 0:08:11 | 0:08:19 | |
Via a device he puts in his mouth. | 0:08:19 | 0:08:22 | |
On the surface are hundreds of tiny electrical stimulators. | 0:08:22 | 0:08:26 | |
When the camera sees an outline, a corresponding line of stimulators buzz away, tickling Erik's tongue. | 0:08:26 | 0:08:36 | |
I can feel each dot and together they create lines and shapes | 0:08:36 | 0:08:42 | |
and ultimately images that my brain then reinterprets as | 0:08:42 | 0:08:48 | |
the space around me. | 0:08:48 | 0:08:50 | |
Decades after he lost his sight, the visual part of Erik's brain is reawakening. | 0:08:50 | 0:08:57 | |
Erik's brain has found a way to connect his mind's eye and his tongue. | 0:09:00 | 0:09:05 | |
Instead of receiving nerve impulses from his dead retina, | 0:09:10 | 0:09:13 | |
his brain's learning to build up a picture of the world based on nerve impulses from his tongue. | 0:09:13 | 0:09:20 | |
Is that sight? | 0:09:20 | 0:09:22 | |
Well, kind of, you know, because I think seeing is more in your brain than in your eyes. | 0:09:22 | 0:09:29 | |
In rock climbing, most of the risk is taken by the lead climber. | 0:09:35 | 0:09:40 | |
Erik is feeling so confident with the brainport device, | 0:09:45 | 0:09:48 | |
that he makes a dramatic decision to lead the final push. | 0:09:48 | 0:09:53 | |
You pop over this lip and it's completely flat and the wind just | 0:10:11 | 0:10:16 | |
gusts in your face and you're up there on this flat tower 1,000 feet above the desert floor. | 0:10:16 | 0:10:22 | |
That was good, thanks. | 0:10:28 | 0:10:30 | |
This is totally beautiful up here. | 0:10:30 | 0:10:33 | |
Erik is living proof of the brain's astonishing ability to remould itself... | 0:10:33 | 0:10:39 | |
and respond to any challenge you throw at it. | 0:10:39 | 0:10:43 | |
Deep inside your head is a remarkably beautiful structure. | 0:10:53 | 0:10:59 | |
A maze of tunnels and caverns submerged in fluid. | 0:10:59 | 0:11:04 | |
These are the semicircular canals | 0:11:04 | 0:11:08 | |
and the cochlea, which are part of your inner ear... | 0:11:08 | 0:11:11 | |
they are crucial for both your balance and hearing. | 0:11:11 | 0:11:16 | |
When sound hits your ear, it sets off a wonderful chain of events. | 0:11:19 | 0:11:24 | |
It enters as pressure waves, which push and pull your ear drum, making it vibrate. | 0:11:29 | 0:11:36 | |
On the other side of the ear drum, slowing time allows us to see | 0:11:39 | 0:11:45 | |
how these vibrations set a series of bones jiggling. | 0:11:45 | 0:11:48 | |
They end with the smallest bone in your entire body, | 0:11:50 | 0:11:53 | |
called the stirrup. It is smaller than a grain of rice. | 0:11:53 | 0:11:57 | |
These bones transmit the vibrations to a sensitive area called the oval window. | 0:11:58 | 0:12:04 | |
They also protect your ear. | 0:12:04 | 0:12:08 | |
If a sound is too loud... | 0:12:08 | 0:12:09 | |
they pull the stirrup away from the most sensitive parts. | 0:12:09 | 0:12:14 | |
Temporarily at least, you go a bit deaf, but the rest of your ear is protected. | 0:12:14 | 0:12:20 | |
Beyond the stirrup is a liquid-filled cavern called your cochlea. | 0:12:22 | 0:12:28 | |
The sound waves enter the water, tickling clumps of tiny hair-like sensors on the floor, | 0:12:28 | 0:12:34 | |
which begin to dance to the sound of the world outside. | 0:12:34 | 0:12:38 | |
Thousands of clusters of hair cells each pick out a different part of the sound. | 0:12:38 | 0:12:44 | |
Each sends a tiny piece of information to your brain, | 0:12:44 | 0:12:48 | |
where it's interpreted so you can make sense of the sounds around you. | 0:12:48 | 0:12:53 | |
The ear has evolved to be most sensitive to the sounds of another voice, | 0:12:58 | 0:13:04 | |
allowing your brain to tune in to the words of another human. | 0:13:04 | 0:13:09 | |
But your ear doesn't just allow you to hear. | 0:13:13 | 0:13:17 | |
It also plays an essential role in allowing you to walk. | 0:13:17 | 0:13:23 | |
For you to take just one step, your brain has to coordinate the precise | 0:13:23 | 0:13:28 | |
movement of over 100 different muscles, bones and tendons. | 0:13:28 | 0:13:33 | |
And there is a place where people learn to walk sooner than anywhere else on Earth. | 0:13:35 | 0:13:42 | |
This is Koarmba. | 0:13:46 | 0:13:48 | |
She is mother to a baby girl called Kossini. | 0:13:48 | 0:13:52 | |
They live in Rhumsiki, a tiny village in the remote northern highlands of Cameroon. | 0:13:52 | 0:13:59 | |
Here, most mothers believe in actively teaching their babies | 0:13:59 | 0:14:02 | |
to stand and walk, to get them off their backs as soon as possible. | 0:14:02 | 0:14:07 | |
And it works. These people have trained their brains to find their feet much earlier than you. | 0:14:09 | 0:14:17 | |
Ever since Kossini was a month old, her mother has repeated the ancient ritual of katete, | 0:14:19 | 0:14:26 | |
which means "to make jump". | 0:14:26 | 0:14:29 | |
Every day, she takes hold under the arms and bounces her. | 0:14:31 | 0:14:35 | |
This daily encouragement helps the gradual development into mature walking. | 0:14:35 | 0:14:40 | |
But before you can stand up for any length of time, | 0:14:40 | 0:14:47 | |
your brain must learn to understand the orientation of your body... | 0:14:47 | 0:14:52 | |
..and that's why your inner ear is so important. | 0:14:54 | 0:14:58 | |
The semi-circular canals that form three twisting tunnels inside your ear | 0:15:03 | 0:15:09 | |
are all orientated in a different direction. | 0:15:09 | 0:15:12 | |
In each lies a saddle-topped fleshy mountain, known as your crista. | 0:15:14 | 0:15:20 | |
The mountain's slopes are covered in a thick forest of tiny hair cells. | 0:15:22 | 0:15:28 | |
For the moment, they lie still, waiting... | 0:15:28 | 0:15:32 | |
But this inner sea never remains calm for long. | 0:15:35 | 0:15:40 | |
Because every now and then... | 0:15:40 | 0:15:42 | |
..there's a tsunami. | 0:15:48 | 0:15:49 | |
A shockwave races through the tunnel and pummels the mountain. | 0:15:58 | 0:16:03 | |
On its flanks, the hair cells are thrown about in the turbulent waters. | 0:16:05 | 0:16:10 | |
The pressure builds until... | 0:16:12 | 0:16:15 | |
electricity flows... | 0:16:15 | 0:16:17 | |
creating a powerful electrical current. | 0:16:21 | 0:16:23 | |
Every time your head moves... | 0:16:28 | 0:16:30 | |
the hairs cells are thrown about inside one or more of the canals. | 0:16:30 | 0:16:35 | |
And in a fraction of a second, electrical impulses are fired straight to your brain. | 0:16:35 | 0:16:41 | |
The feeling that emerges is your sense of balance. | 0:16:43 | 0:16:47 | |
To walk, your brain | 0:16:50 | 0:16:52 | |
has to learn to sense when you are over-balancing to one side... | 0:16:52 | 0:16:57 | |
and then instruct your leg to bring your weight back to the centre. | 0:16:58 | 0:17:05 | |
All of this happens within a fraction of a second. | 0:17:05 | 0:17:10 | |
To begin with, it's a real struggle. | 0:17:13 | 0:17:17 | |
But Kossini's half brother | 0:17:17 | 0:17:20 | |
is already a master of bipedalism. | 0:17:20 | 0:17:24 | |
And he is just ten months old. | 0:17:24 | 0:17:27 | |
From now on, and for the rest of his life, walking will be automatic. | 0:17:27 | 0:17:32 | |
The amazing construction of your ear allows you to both sense and explore the planet you inhabit. | 0:17:35 | 0:17:42 | |
For nine months, you were enveloped in the warm, comfortable world of your mother's womb. | 0:17:50 | 0:17:57 | |
Your every need was taken care of. | 0:17:59 | 0:18:02 | |
The placenta supplied you with oxygen from your mother's blood, | 0:18:02 | 0:18:07 | |
so your own lungs were hardly used. | 0:18:07 | 0:18:09 | |
At this stage of your life, your heart had completely different plumbing... | 0:18:09 | 0:18:15 | |
a hole through its centre diverted blood away from your lungs almost entirely. | 0:18:15 | 0:18:23 | |
And then, suddenly, your tranquillity was shattered. | 0:18:23 | 0:18:27 | |
Relax... | 0:18:31 | 0:18:33 | |
Relax. | 0:18:36 | 0:18:38 | |
As you were born, | 0:18:43 | 0:18:45 | |
you went through the most dramatic minute of your life as your body took over from your mother's. | 0:18:45 | 0:18:52 | |
Once out into the world, you were bombarded with new stimuli. | 0:18:52 | 0:18:58 | |
Bright glaring lights... | 0:18:58 | 0:19:00 | |
Cold air on your skin... | 0:19:00 | 0:19:02 | |
Strange sounds. | 0:19:04 | 0:19:06 | |
Scientists now believe it's the shock of these stimuli that triggers your first critical breath. | 0:19:08 | 0:19:15 | |
But before you can absorb life-giving oxygen, your circulation must be rapidly re-plumbed. | 0:19:20 | 0:19:28 | |
As you draw your first breath... | 0:19:32 | 0:19:35 | |
The airways of your lungs open, causing blood to rush into them to pick up oxygen... | 0:19:35 | 0:19:42 | |
That oxygen-rich blood then flows out of the lungs and into the heart. | 0:19:43 | 0:19:48 | |
As it does so, pressure builds up, closing a flap over the hole. | 0:19:52 | 0:19:57 | |
This hole will, in time, seal completely. | 0:19:59 | 0:20:02 | |
Your circulation is now complete. | 0:20:02 | 0:20:05 | |
Oxygen-rich blood can flow from your heart to the rest of your body... | 0:20:06 | 0:20:12 | |
deoxygenated blood flows back to your heart and to the lungs, where you get new oxygen. | 0:20:12 | 0:20:18 | |
So now you can take another breath... | 0:20:21 | 0:20:25 | |
and another... | 0:20:25 | 0:20:27 | |
for the rest of your life... | 0:20:27 | 0:20:28 | |
Your heart's will to beat, to keep going, is incredibly strong. | 0:20:38 | 0:20:43 | |
If the heart fails, so does everything else... | 0:20:43 | 0:20:47 | |
Because it's your heart's job to deliver to every cell, to every nook and cranny of your body, | 0:20:47 | 0:20:54 | |
the substance which keeps it alive - oxygen. | 0:20:54 | 0:20:59 | |
But how does the body do this? | 0:20:59 | 0:21:02 | |
The hard graft of carrying oxygen is done by some of the smallest | 0:21:05 | 0:21:10 | |
and most peculiar cells in your body. | 0:21:10 | 0:21:13 | |
These red blood cells are well suited to the job of carrying oxygen around your body. | 0:21:13 | 0:21:21 | |
Each red blood cell contains millions of haemoglobin proteins. | 0:21:21 | 0:21:26 | |
They have a structure that oxygen likes to bind to. | 0:21:26 | 0:21:30 | |
Haemoglobin is bulky, so there's not much space for anything else | 0:21:33 | 0:21:36 | |
inside the red blood cells, which have to squeeze into tiny blood vessels. | 0:21:36 | 0:21:43 | |
It means that red blood cells are unique amongst all your cells, | 0:21:43 | 0:21:47 | |
because to carry oxygen, they don't have a nucleus. | 0:21:47 | 0:21:50 | |
25 trillion red blood cells are pumped around the body, completing a circuit within a minute. | 0:21:53 | 0:22:01 | |
Each cell makes a tortuous journey... | 0:22:03 | 0:22:07 | |
through wide arteries that surge like a river in full flood. | 0:22:07 | 0:22:12 | |
Then branching off into smaller streams called arterioles. | 0:22:12 | 0:22:16 | |
It's perfectly shaped to squeeze through tiny, slow-moving capillaries. | 0:22:22 | 0:22:29 | |
And without a fat nucleus, it just about gets through. | 0:22:29 | 0:22:32 | |
Here, in the smallest, narrowest vessels, our cell does the job it's built for... | 0:22:34 | 0:22:40 | |
it releases its payload of oxygen into the tissues. | 0:22:40 | 0:22:44 | |
The reason that your body goes to such lengths to ensure a steady supply of oxygen | 0:22:49 | 0:22:55 | |
is because oxygen is an essential ingredient in unlocking the energy you need to survive. | 0:22:55 | 0:23:02 | |
Oxygen from the red blood cells passes into every other cell of your body. | 0:23:10 | 0:23:15 | |
Here, there are hundreds of little powerhouses called mitochondria. | 0:23:21 | 0:23:26 | |
They burn oxygen to release all the energy you need to live your life. | 0:23:27 | 0:23:33 | |
But to do this, they need another ingredient | 0:23:41 | 0:23:45 | |
which also comes via the bloodstream... | 0:23:45 | 0:23:50 | |
food. | 0:23:50 | 0:23:51 | |
Food is mainly absorbed in the small intestine, which is covered in | 0:23:55 | 0:24:00 | |
finger-like projections called villi and microvilli. | 0:24:00 | 0:24:05 | |
They increase the surface area of your gut to that of a tennis court, | 0:24:05 | 0:24:11 | |
so you can absorb as many nutrients as possible. | 0:24:11 | 0:24:14 | |
If you eat a packet of crisps, for example, it is here that the crisps will be broken down into smaller | 0:24:17 | 0:24:24 | |
and smaller particles, until they are reduced to glucose... | 0:24:24 | 0:24:28 | |
which is small enough to be absorbed into the bloodstream, | 0:24:28 | 0:24:32 | |
ready to be transported to the mitochondria in your cells. | 0:24:32 | 0:24:37 | |
Over your lifetime, you will eat more than 50 tons of food, and take over 800 million breaths, which you | 0:24:39 | 0:24:47 | |
will convert into enough energy to power a house for five years. | 0:24:47 | 0:24:51 | |
And every mouthful and every breath has finished here, with your | 0:24:54 | 0:24:58 | |
mitochondria using the energy released to get you through the day. | 0:24:58 | 0:25:03 | |
Your heart is an exquisitely engineered pump made almost entirely of muscle. | 0:25:11 | 0:25:18 | |
And you can see the extraordinary engineering in action if we slow your heart to a single beat. | 0:25:18 | 0:25:24 | |
Inside the cavernous chambers, the muscles work together in perfect harmony. | 0:25:30 | 0:25:35 | |
These muscles never get tired and never stop working until you die. | 0:25:42 | 0:25:47 | |
As your heart expands, blood flows from your body into its chambers. | 0:25:50 | 0:25:55 | |
First the atria, | 0:25:57 | 0:25:59 | |
then the ventricles. | 0:25:59 | 0:26:01 | |
The left ventricle has to work particularly hard, because each of its contractions must have | 0:26:04 | 0:26:10 | |
enough power to push blood all the way through your body's vast network of blood vessels. | 0:26:10 | 0:26:16 | |
And that's a long way. If they were strung together, these vessels would circle the Earth at least twice. | 0:26:18 | 0:26:26 | |
Like the plumbing in your house, your heart needs valves | 0:26:28 | 0:26:31 | |
between its chambers and arteries to stop the blood flowing backwards. | 0:26:31 | 0:26:36 | |
As the valves slam shut, they make the familiar "lub-dub, lub-dub" sound | 0:26:39 | 0:26:45 | |
of the heartbeat in your chest. | 0:26:45 | 0:26:47 | |
Every single minute, your heart does this around 70 times. | 0:26:49 | 0:26:55 | |
And it's all regulated by some little cells at its core... | 0:26:56 | 0:27:00 | |
At the start of your life, | 0:27:04 | 0:27:06 | |
when you were just a three-week-old embryo, something happened | 0:27:06 | 0:27:11 | |
inside your body which was nothing short of a miracle... | 0:27:11 | 0:27:14 | |
These tireless cells - | 0:27:16 | 0:27:18 | |
called pacemakers, which control the beat of your heart - came into being... | 0:27:18 | 0:27:22 | |
They spontaneously beat out a rhythm... | 0:27:24 | 0:27:27 | |
sending synchronised signals through your heart. | 0:27:27 | 0:27:30 | |
Which speed up or slow down, according to what your body's doing. | 0:27:30 | 0:27:35 | |
And these pacemaker cells will stay with you always... | 0:27:37 | 0:27:40 | |
..faithfully responding to every demand of your life. | 0:27:42 | 0:27:47 | |
Katlyn Hagan will be relying on her pacemaker cells to do something extraordinary. | 0:27:50 | 0:27:57 | |
She needs to have major heart surgery... | 0:27:57 | 0:28:00 | |
her heart will be stopped for anything up to an hour. | 0:28:00 | 0:28:04 | |
There is a risk of death with heart surgery. I hate saying it, it's not zero. | 0:28:04 | 0:28:07 | |
I have a great team and we'll take great care of you tomorrow, I promise you. | 0:28:07 | 0:28:11 | |
We'll do everything we can for you. | 0:28:11 | 0:28:12 | |
I'm very scared. | 0:28:19 | 0:28:20 | |
I want to make sure I'm still living after my operation | 0:28:21 | 0:28:25 | |
so I can be there for my daughters growing up | 0:28:25 | 0:28:30 | |
and just live a normal life. | 0:28:31 | 0:28:34 | |
The operation will be tricky. | 0:28:39 | 0:28:43 | |
It's the very same pacemaker cells that keep Katlyn alive which are causing her problem. | 0:28:43 | 0:28:48 | |
But before they can operate, they must transfer the job of | 0:28:55 | 0:28:59 | |
pumping blood around Katlyn's body to a machine... | 0:28:59 | 0:29:02 | |
..and then stop her heart. | 0:29:05 | 0:29:08 | |
See it gradually slowing down. | 0:29:08 | 0:29:10 | |
As the fluid goes in, the heart gets a little whiter, | 0:29:10 | 0:29:14 | |
cos there's no blood going into it. | 0:29:14 | 0:29:17 | |
Without a heartbeat, | 0:29:21 | 0:29:22 | |
Katlyn is in a hinterland between life and death. | 0:29:22 | 0:29:27 | |
Now they can begin to remove the faulty pacemaker cells. | 0:29:29 | 0:29:33 | |
To do this, the surgeons use a cryoprobe, | 0:29:33 | 0:29:36 | |
which freezes and destroys them. | 0:29:36 | 0:29:39 | |
They have to be careful | 0:29:41 | 0:29:42 | |
to remove only the cells which are malfunctioning. | 0:29:42 | 0:29:45 | |
The main procedure is finished. | 0:29:52 | 0:29:55 | |
It's time to get Katlyn off the bypass machine | 0:29:55 | 0:29:58 | |
and reconnect her heart. | 0:29:58 | 0:29:59 | |
By now, her heart has been stopped for nearly an hour... | 0:30:04 | 0:30:09 | |
The heart's starting to get blood right now. | 0:30:09 | 0:30:14 | |
So we're inflating the lungs. | 0:30:14 | 0:30:17 | |
As blood flows back into Katlyn's heart, | 0:30:17 | 0:30:19 | |
its warmth and nutrients | 0:30:19 | 0:30:21 | |
are enough to re-start the pacemaker cells. | 0:30:21 | 0:30:25 | |
All right. Come on. | 0:30:25 | 0:30:27 | |
-MACHINE BEEPS -And the rhythm returns. | 0:30:29 | 0:30:32 | |
It looks good. | 0:30:32 | 0:30:34 | |
The operation has been a success. | 0:30:39 | 0:30:42 | |
Katlyn's heart is now beating correctly. | 0:30:47 | 0:30:52 | |
Driven by a group of pacemaker cells | 0:30:52 | 0:30:55 | |
created within weeks of her conception. | 0:30:55 | 0:30:58 | |
These cells will remain with her | 0:30:58 | 0:31:01 | |
until her last heartbeat. | 0:31:01 | 0:31:03 | |
We are all born with a shield | 0:31:08 | 0:31:11 | |
which protects us from the dangers of the outside world. | 0:31:11 | 0:31:15 | |
It's our first line of defence - | 0:31:15 | 0:31:17 | |
our skin. | 0:31:17 | 0:31:19 | |
Your skin is amazing. | 0:31:21 | 0:31:24 | |
The largest organ in your body - | 0:31:24 | 0:31:26 | |
up to two meters squared. | 0:31:26 | 0:31:29 | |
Each centimetre of skin is built from ten million individual cells. | 0:31:32 | 0:31:37 | |
This tiny square bristles with over 100 hairs. | 0:31:40 | 0:31:44 | |
And packs 100 sensors | 0:31:46 | 0:31:48 | |
that can detect the lightest of touches. | 0:31:48 | 0:31:51 | |
But it must also act as an impenetrable barrier. | 0:31:51 | 0:31:54 | |
Because your skin | 0:31:56 | 0:31:58 | |
is covered in millions of bacteria. | 0:31:58 | 0:32:01 | |
If they get inside your body, | 0:32:01 | 0:32:03 | |
your warm, moist tissues | 0:32:03 | 0:32:05 | |
will provide the perfect environment | 0:32:05 | 0:32:08 | |
for them to take over. | 0:32:08 | 0:32:09 | |
What prevents them getting in | 0:32:09 | 0:32:12 | |
is the clever way your skin is constructed. | 0:32:12 | 0:32:15 | |
Skin cells lock together like armour plates. | 0:32:15 | 0:32:18 | |
And it's not just passive protection, | 0:32:22 | 0:32:24 | |
your skin is constantly pushing outwards. | 0:32:24 | 0:32:27 | |
New layers grow underneath the old | 0:32:29 | 0:32:32 | |
and push the surface layers away. | 0:32:32 | 0:32:35 | |
This constant shedding | 0:32:35 | 0:32:36 | |
prevents most microbes | 0:32:36 | 0:32:38 | |
from getting a permanent hold. | 0:32:38 | 0:32:40 | |
However, it also means you lose 30,000 skin cells every day. | 0:32:42 | 0:32:47 | |
This time next month, | 0:32:49 | 0:32:51 | |
you'll have replaced all the skin on your body. | 0:32:51 | 0:32:54 | |
But your skin doesn't just protect you from living organisms. | 0:32:59 | 0:33:03 | |
It also needs to keep your internal organs safe from getting dehydrated. | 0:33:05 | 0:33:10 | |
At the base of every hair on your body is a tiny gland, | 0:33:14 | 0:33:19 | |
known as a sebaceous gland. | 0:33:19 | 0:33:22 | |
It protects you by squeezing an oily substance call Sebum | 0:33:23 | 0:33:28 | |
onto the surface of your skin. | 0:33:28 | 0:33:31 | |
Sebum is what makes your hair greasy. | 0:33:31 | 0:33:34 | |
And what gives you spots | 0:33:34 | 0:33:36 | |
and makes your skin waterproof. | 0:33:36 | 0:33:39 | |
This oil helps to prevent fluids inside your body | 0:33:40 | 0:33:44 | |
from evaporating into the air, | 0:33:44 | 0:33:47 | |
which can cause dehydration. | 0:33:47 | 0:33:49 | |
Your skin is constantly working in two directions. | 0:33:51 | 0:33:54 | |
Firstly, to stop bacteria from getting into your body. | 0:33:56 | 0:34:01 | |
And secondly, to protect the organs inside your body from drying out. | 0:34:01 | 0:34:06 | |
It's a perfectly-engineered protective layer. | 0:34:06 | 0:34:10 | |
Every minute of your life | 0:34:18 | 0:34:20 | |
your body is silently performing a host of small miracles | 0:34:20 | 0:34:24 | |
to keep you alive. | 0:34:24 | 0:34:26 | |
But all of them would stop, and you with them, | 0:34:26 | 0:34:30 | |
if one crucial factor in your body | 0:34:30 | 0:34:32 | |
were to change dramatically. | 0:34:32 | 0:34:35 | |
And that's your temperature. | 0:34:35 | 0:34:37 | |
Your body is designed to function at 37 degrees centigrade. | 0:34:37 | 0:34:43 | |
When your body overheats, | 0:34:48 | 0:34:50 | |
it stimulates sweat glands deep within your skin. | 0:34:50 | 0:34:55 | |
They produce beads of sweat. | 0:34:55 | 0:34:58 | |
Which work their way out of your body | 0:34:58 | 0:35:01 | |
and onto your skin's surface. | 0:35:01 | 0:35:03 | |
And it's here that sweat does it's work. | 0:35:06 | 0:35:09 | |
It cools your body by evaporating into the air... | 0:35:13 | 0:35:18 | |
keeping you alive when things hot up. | 0:35:20 | 0:35:24 | |
Extreme heat can be deadly. | 0:35:28 | 0:35:31 | |
For these elite firefighters in Texas, | 0:35:37 | 0:35:40 | |
their body's ability to keep their temperature constant | 0:35:40 | 0:35:43 | |
is a matter of life and death. | 0:35:43 | 0:35:45 | |
Their triple-lined fire suits | 0:35:45 | 0:35:48 | |
do much to protect them from the flames. | 0:35:48 | 0:35:50 | |
But there's something else - | 0:35:52 | 0:35:55 | |
their ability to sweat. | 0:35:55 | 0:35:57 | |
Firefighter Mario Rodriguez | 0:36:02 | 0:36:05 | |
is getting weighed to see how much sweat he looses | 0:36:05 | 0:36:08 | |
when fighting a fire. | 0:36:08 | 0:36:09 | |
To measure any temperature change inside his body, | 0:36:11 | 0:36:14 | |
Rodriguez takes an electronic pill. | 0:36:14 | 0:36:17 | |
To keep his heart and brain safe, | 0:36:17 | 0:36:19 | |
his core temperature must remain close to 37 degrees centigrade. | 0:36:19 | 0:36:24 | |
Before he goes in, his core temperature is just over 37 degrees. | 0:36:32 | 0:36:37 | |
If his core temperature rises by just four degrees | 0:36:50 | 0:36:54 | |
he will become confused and fall unconscious. | 0:36:54 | 0:36:58 | |
A rise of six degrees could cause death. | 0:36:58 | 0:37:00 | |
After 45 seconds in the 1,200 degree fire... | 0:37:04 | 0:37:10 | |
he's poaching in his own juices. | 0:37:10 | 0:37:14 | |
'It was real hot, | 0:37:29 | 0:37:30 | |
'my bones and all my joints were burning.' | 0:37:30 | 0:37:34 | |
The heat... Just got to get out of there and get some cool air. | 0:37:34 | 0:37:37 | |
His core temperature has risen by a very minimal one degree centigrade. | 0:37:37 | 0:37:43 | |
You're at 207 now. | 0:37:46 | 0:37:48 | |
So that looks like you lost three pounds of body weight. | 0:37:48 | 0:37:51 | |
Three pounds equals over a litre of sweat | 0:37:51 | 0:37:54 | |
lost in just one minute's exposure to the fire. | 0:37:54 | 0:37:58 | |
Rodriguez walked into a 1,200 degree fire | 0:38:00 | 0:38:04 | |
and walked out with his body temperature almost exactly the same. | 0:38:04 | 0:38:09 | |
This is the story of your creation. | 0:38:17 | 0:38:21 | |
It began with a sperm, | 0:38:27 | 0:38:29 | |
the smallest cell in the human body, | 0:38:29 | 0:38:32 | |
fusing with the biggest cell... | 0:38:32 | 0:38:34 | |
an egg. | 0:38:34 | 0:38:35 | |
Everyday, the human male | 0:38:40 | 0:38:41 | |
produces hundreds of millions of DNA Torpedoes... | 0:38:41 | 0:38:48 | |
otherwise known as sperm. | 0:38:48 | 0:38:50 | |
Each ejaculation can contain 250 million of them. | 0:38:51 | 0:38:56 | |
That's enough, at least in theory, | 0:38:58 | 0:39:01 | |
to cover every inch of Manhattan with people. | 0:39:01 | 0:39:05 | |
Fortunately, the human female has other ideas. | 0:39:08 | 0:39:12 | |
For her, it's quality, not quantity. | 0:39:12 | 0:39:16 | |
Her ovaries usually produce just one egg every month. | 0:39:18 | 0:39:23 | |
The process of reproduction is so complex | 0:39:27 | 0:39:31 | |
it's a wonder it happens at all. | 0:39:31 | 0:39:34 | |
Most of the time, the sperm die in a pool, | 0:39:35 | 0:39:39 | |
trapped inside the vagina. | 0:39:39 | 0:39:41 | |
Because the entrance into the womb, through the cervix, | 0:39:42 | 0:39:47 | |
is out of reach, blocked shut. | 0:39:47 | 0:39:50 | |
For the sperm to have a chance of getting in, | 0:39:50 | 0:39:54 | |
timing is everything. | 0:39:54 | 0:39:55 | |
There are just a few days in any month | 0:40:03 | 0:40:06 | |
when the woman's body offers them an opportunity. | 0:40:06 | 0:40:09 | |
Hormones soften the blockage | 0:40:09 | 0:40:11 | |
at the entrance to the cervix. | 0:40:11 | 0:40:15 | |
Transforming it from a barrier into a life line. | 0:40:15 | 0:40:18 | |
But the sperm have to be strong | 0:40:23 | 0:40:25 | |
to make the 15cm journey. | 0:40:25 | 0:40:27 | |
It's a long way | 0:40:27 | 0:40:29 | |
for the smallest cell in the body. | 0:40:29 | 0:40:32 | |
The straighter and faster they can swim, | 0:40:32 | 0:40:35 | |
the better chance they have of making it. | 0:40:35 | 0:40:37 | |
The deformed, lazy and the dead | 0:40:37 | 0:40:40 | |
are left behind. | 0:40:40 | 0:40:42 | |
And, of course, | 0:40:44 | 0:40:45 | |
the more fit sperm you have, | 0:40:45 | 0:40:47 | |
the greater the chance of success. | 0:40:47 | 0:40:49 | |
If 250 million sperm began the journey, | 0:40:53 | 0:40:57 | |
only 1%, that's two and a half million, | 0:40:57 | 0:41:00 | |
will make it through to the cervix. | 0:41:00 | 0:41:03 | |
As they swim out of the vagina, | 0:41:05 | 0:41:07 | |
they're just at the beginning of a long and perilous journey. | 0:41:07 | 0:41:11 | |
The woman's body is about to launch an attack. | 0:41:17 | 0:41:22 | |
They have entered the cervix - | 0:41:22 | 0:41:26 | |
a labyrinth of dead ends. | 0:41:26 | 0:41:28 | |
perfect for an ambush. | 0:41:28 | 0:41:31 | |
The sperm have triggered the body's defence system. | 0:41:33 | 0:41:36 | |
White blood cells have recognised the sperm as a foreign invader | 0:41:38 | 0:41:42 | |
and, just as they would if they were fighting an infection, | 0:41:42 | 0:41:45 | |
they've been mobilised to kill. | 0:41:45 | 0:41:48 | |
They attack the sperm | 0:41:50 | 0:41:52 | |
as they swim through the cervix and into the uterus. | 0:41:52 | 0:41:55 | |
By the time the surviving sperm reach the fallopian tube, | 0:42:01 | 0:42:04 | |
where they are safe from the white blood cells | 0:42:04 | 0:42:08 | |
there could be as few as 20 left. | 0:42:08 | 0:42:10 | |
They will be 20 of the very best on offer. | 0:42:12 | 0:42:15 | |
Here, scientists have recently discovered | 0:42:20 | 0:42:23 | |
that the woman's body | 0:42:23 | 0:42:24 | |
has come up with an amazing trick. | 0:42:24 | 0:42:26 | |
She takes control of the sperm by holding them, one by one, | 0:42:29 | 0:42:32 | |
on the walls of her fallopian tube. | 0:42:32 | 0:42:36 | |
She then powers them down. | 0:42:38 | 0:42:40 | |
They're alive, safe, but fast asleep. | 0:42:42 | 0:42:45 | |
The woman now has up to five days | 0:42:52 | 0:42:54 | |
to release the precious egg growing inside her ovary. | 0:42:54 | 0:42:58 | |
As soon as it's ripe, the egg is released. | 0:43:07 | 0:43:10 | |
And it's wafted into the opening of the fallopian tube. | 0:43:16 | 0:43:20 | |
Once the egg is ready and waiting, | 0:43:31 | 0:43:33 | |
it's time to wake up the sleeping sperm... | 0:43:33 | 0:43:36 | |
Sending out a powerful chemical beacon, | 0:43:43 | 0:43:45 | |
the egg guides the sperm in. | 0:43:45 | 0:43:48 | |
It's the precursor of every new life. | 0:43:54 | 0:43:57 | |
The sperm - some male, some female - | 0:44:00 | 0:44:03 | |
compete to reach the egg. | 0:44:03 | 0:44:05 | |
But there can be only one winner. | 0:44:11 | 0:44:14 | |
The competing sperm break off the surrounding cloud of cells. | 0:44:19 | 0:44:24 | |
Until one finally pushes through | 0:44:27 | 0:44:29 | |
the soft shell underneath. | 0:44:29 | 0:44:31 | |
The egg is now in danger. | 0:44:39 | 0:44:41 | |
If a second sperm gets in, | 0:44:44 | 0:44:46 | |
the egg will die. | 0:44:46 | 0:44:49 | |
It must protect itself - and quickly. | 0:44:52 | 0:44:55 | |
Under the shell, | 0:44:58 | 0:44:59 | |
tiny granules detonate in a chain reaction. | 0:44:59 | 0:45:03 | |
Firing out chemicals, | 0:45:03 | 0:45:05 | |
hardening the shell, | 0:45:05 | 0:45:07 | |
making the egg impenetrable. | 0:45:07 | 0:45:09 | |
Fertilised, the egg is now safe. | 0:45:11 | 0:45:14 | |
This was how we all began. | 0:45:16 | 0:45:19 | |
You truly are an amazing creation. | 0:45:19 | 0:45:22 | |
We're made up of around a hundred trillion cells, | 0:45:29 | 0:45:33 | |
all coming from just one single fertilised egg. | 0:45:33 | 0:45:37 | |
Within hours of fertilisation, | 0:45:39 | 0:45:42 | |
this new cell, called a zygote, | 0:45:42 | 0:45:44 | |
divided into two identical cells. | 0:45:44 | 0:45:47 | |
Then into four... | 0:45:47 | 0:45:49 | |
then eight... | 0:45:49 | 0:45:50 | |
16, and so on... | 0:45:50 | 0:45:53 | |
before implanting in the lining of the womb | 0:45:54 | 0:45:57 | |
and becoming an embryo. | 0:45:57 | 0:45:59 | |
In some cases, on rare occasions, | 0:46:05 | 0:46:09 | |
a single embryo creates two bodies. | 0:46:09 | 0:46:12 | |
one in 250 early embryos split. | 0:46:16 | 0:46:21 | |
If they do, | 0:46:21 | 0:46:22 | |
they must divide completely | 0:46:22 | 0:46:24 | |
within the first two weeks, | 0:46:24 | 0:46:26 | |
or they probably never will. | 0:46:26 | 0:46:28 | |
Once split, the embryos create near-replicas of themselves. | 0:46:31 | 0:46:35 | |
Identical twins. | 0:46:35 | 0:46:38 | |
This quirk of nature | 0:46:40 | 0:46:41 | |
has given synchronised divers, Helen and Carol Galashan | 0:46:41 | 0:46:45 | |
a distinct advantage. | 0:46:45 | 0:46:47 | |
Being an identical twin | 0:46:47 | 0:46:49 | |
definitely helps with synchronised diving. | 0:46:49 | 0:46:51 | |
We don't really have to try with the synchronised part, | 0:46:51 | 0:46:54 | |
that part comes quite naturally to us. | 0:46:54 | 0:46:56 | |
We actually think we're mirror-image twins. | 0:46:56 | 0:46:58 | |
-We fold our arms opposite ways. Our hair parts the opposite way. -Even when we're diving, | 0:46:58 | 0:47:02 | |
The first foot I put on is my right foot, Carol's is her left foot. | 0:47:02 | 0:47:06 | |
Identical twins actually come from one egg... | 0:47:07 | 0:47:11 | |
-That splits. -That splits into two, and non-identical twins come from two eggs. | 0:47:11 | 0:47:15 | |
So the way we see it is that we were one person that split in two... | 0:47:15 | 0:47:18 | |
One person in two bodies. | 0:47:18 | 0:47:20 | |
-Right... -Ooh. | 0:47:23 | 0:47:25 | |
This woman's pregnancy is even more unlikely than identical twins. | 0:47:27 | 0:47:31 | |
She's beaten odds of 4,500 to 1. | 0:47:33 | 0:47:37 | |
Diane is carrying non-identical triplets. | 0:47:37 | 0:47:41 | |
Remarkably, Diane's body | 0:47:41 | 0:47:43 | |
naturally produced not one, but three eggs in a single go. | 0:47:43 | 0:47:48 | |
It's an incredibly rare type of pregnancy. | 0:47:49 | 0:47:52 | |
Not only did Diane produce multiple eggs, | 0:47:52 | 0:47:55 | |
but all of them were fertilised. | 0:47:55 | 0:47:57 | |
Entirely independently of each other. | 0:47:57 | 0:48:00 | |
Apparently, I released three eggs, | 0:48:01 | 0:48:04 | |
and Mike, he had three separate sperm | 0:48:04 | 0:48:06 | |
that fertilised all three eggs. | 0:48:06 | 0:48:08 | |
They've all got their own placentas | 0:48:08 | 0:48:11 | |
and they're all in separate sacks. | 0:48:11 | 0:48:13 | |
So they've all got have their own little bedroom. | 0:48:13 | 0:48:17 | |
Effectively, Diane got pregnant three times in one go. | 0:48:18 | 0:48:22 | |
But there's a downside to having triplets. | 0:48:28 | 0:48:32 | |
31 weeks - nine weeks early - | 0:48:32 | 0:48:34 | |
Diane has gone into labour. | 0:48:34 | 0:48:37 | |
She is going to need an emergency caesarean. | 0:48:37 | 0:48:40 | |
I'm just going to bring him round to show you, quickly. | 0:48:46 | 0:48:50 | |
Here we go, you two. Here he is. He's beautiful. | 0:48:50 | 0:48:54 | |
So he's a little breach baby. | 0:48:56 | 0:48:59 | |
There he is. | 0:48:59 | 0:49:01 | |
-Hello! -Isn't he lovely? | 0:49:01 | 0:49:03 | |
This is the skinny Minnie. | 0:49:07 | 0:49:10 | |
All the babies have now been delivered. | 0:49:10 | 0:49:12 | |
-She's beautiful. -Last but not least. | 0:49:12 | 0:49:15 | |
And against the odds, | 0:49:15 | 0:49:17 | |
they are all alive and well. | 0:49:17 | 0:49:19 | |
For your body, | 0:49:28 | 0:49:30 | |
this world is a dangerous place. | 0:49:30 | 0:49:32 | |
Threats lurk around every corner. | 0:49:35 | 0:49:38 | |
And it's not just the obvious dangers that threaten you. | 0:49:38 | 0:49:42 | |
Even now, as you watch this film, | 0:49:44 | 0:49:46 | |
there are pathogens waiting to get inside you. | 0:49:46 | 0:49:49 | |
A pathogen is a foreign invader that causes disease. | 0:49:49 | 0:49:53 | |
They spread in all sorts of ways, | 0:49:55 | 0:49:59 | |
commonly through sneezing. | 0:49:59 | 0:50:02 | |
A simple sneeze | 0:50:02 | 0:50:04 | |
is often all it takes | 0:50:04 | 0:50:06 | |
for viruses to jump from one person to another. | 0:50:06 | 0:50:09 | |
Sneezing is one of the most powerful forces your body produces. | 0:50:09 | 0:50:13 | |
You expel air at 100 miles an hour, | 0:50:13 | 0:50:16 | |
ejecting anything that isn't bolted down. | 0:50:16 | 0:50:19 | |
Once a pathogen invader, like the flu virus, | 0:50:21 | 0:50:25 | |
gets inside your body, | 0:50:25 | 0:50:26 | |
you have to respond quickly. | 0:50:26 | 0:50:28 | |
Time to turn on your immune system | 0:50:30 | 0:50:33 | |
to destroy them. | 0:50:33 | 0:50:34 | |
Your first response to infection is fever. | 0:50:39 | 0:50:43 | |
Raising your temperature by just a few degrees | 0:50:43 | 0:50:46 | |
is enough to slow them down. | 0:50:46 | 0:50:48 | |
Meanwhile, deep within your tissues, | 0:50:54 | 0:50:57 | |
an internal army is on the march. | 0:50:57 | 0:51:00 | |
On the frontline are phagocytes, | 0:51:02 | 0:51:04 | |
a form of white blood cell. | 0:51:04 | 0:51:07 | |
They flood the infection site to fight the viruses. | 0:51:07 | 0:51:10 | |
But in this case, the viruses are too strong. | 0:51:12 | 0:51:16 | |
Instead, the soldiers themselves become infected. | 0:51:16 | 0:51:20 | |
Now the only way these cells can kill the viruses | 0:51:20 | 0:51:23 | |
is to self-destruct. | 0:51:23 | 0:51:25 | |
As their bodies pile up, | 0:51:29 | 0:51:33 | |
they form the sticky basis of your snot. | 0:51:33 | 0:51:36 | |
But your immune system hasn't given up. | 0:51:38 | 0:51:40 | |
A second wave of attack is released | 0:51:43 | 0:51:45 | |
as another kind of white blood cell is unleashed... | 0:51:45 | 0:51:49 | |
the Killer T-cells. | 0:51:49 | 0:51:52 | |
Instead of attacking the viruses directly, | 0:51:52 | 0:51:56 | |
they take aim at your own infected cells. | 0:51:56 | 0:51:59 | |
They give a kiss of death, | 0:51:59 | 0:52:02 | |
they make the infected cell implode, | 0:52:02 | 0:52:06 | |
then self destruct, | 0:52:06 | 0:52:08 | |
destroying the viruses inside. | 0:52:08 | 0:52:12 | |
It's one of the reasons you'll get a sore throat. | 0:52:12 | 0:52:14 | |
Despite these two assaults, | 0:52:21 | 0:52:23 | |
the viruses haven't yet been defeated. | 0:52:23 | 0:52:26 | |
But your immune system has another trick. | 0:52:26 | 0:52:30 | |
Yet more white bloods cells, | 0:52:30 | 0:52:31 | |
this time called B-cells, | 0:52:31 | 0:52:33 | |
are able to recognise the specific invading pathogen | 0:52:33 | 0:52:36 | |
and produce a specialised weapon. | 0:52:36 | 0:52:39 | |
The Y-shaped antibody. | 0:52:42 | 0:52:44 | |
These can be produced at a rate of 2,000 per cell per second. | 0:52:46 | 0:52:53 | |
They coat the viruses... | 0:52:53 | 0:52:55 | |
slowing them down and making them stick together. | 0:52:56 | 0:53:00 | |
Now the viruses are easily swept up. | 0:53:00 | 0:53:03 | |
And you begin to feel better, | 0:53:08 | 0:53:11 | |
the fever drops and your energy starts to return. | 0:53:11 | 0:53:14 | |
The cells of your immune system | 0:53:16 | 0:53:19 | |
have won the day. | 0:53:19 | 0:53:20 | |
One of the most remarkable defence mechanisms your body has | 0:53:29 | 0:53:33 | |
is its ability to repair itself. | 0:53:33 | 0:53:35 | |
Johnny Greaves is 33 years old. | 0:53:39 | 0:53:42 | |
He is a professional boxer. | 0:53:42 | 0:53:44 | |
For Johnny, boxing isn't just a sport, it's a livelihood. | 0:53:45 | 0:53:48 | |
I'm here to pay my bills and keep my kids OK, | 0:53:51 | 0:53:53 | |
so obviously, that's the first thought in my mind, | 0:53:53 | 0:53:56 | |
bringing home the bacon and paying the kids' bills. | 0:53:56 | 0:53:59 | |
Johnny is in a dangerous game. | 0:54:01 | 0:54:03 | |
If he picks up the slightest injury, | 0:54:03 | 0:54:06 | |
boxing regulations mean he'll have to cancel his next fight. | 0:54:06 | 0:54:10 | |
If he show's up with a bruise he'll be disqualified. | 0:54:13 | 0:54:16 | |
His body is going to do everything in its power to avoid this. | 0:54:20 | 0:54:24 | |
All of Johnny's biological defence mechanisms | 0:54:26 | 0:54:29 | |
are clicking into action. | 0:54:29 | 0:54:30 | |
He ducks and dives | 0:54:30 | 0:54:32 | |
to avoid the punches. | 0:54:32 | 0:54:34 | |
But as Johnny tires, his defences begin to fail. | 0:54:41 | 0:54:44 | |
The full extent of Johnny's injuries have yet to be revealed. | 0:54:58 | 0:55:03 | |
A black eye is about to form. | 0:55:03 | 0:55:05 | |
His next fight is in two weeks, | 0:55:07 | 0:55:09 | |
if he is to collect that pay cheque | 0:55:09 | 0:55:11 | |
he has to heal. | 0:55:11 | 0:55:14 | |
Now its time for Johnny's body to really earn his living. | 0:55:14 | 0:55:17 | |
The delicate blood vessels in the tissue under Johnny's eye | 0:55:24 | 0:55:27 | |
were destroyed by a single punch. | 0:55:27 | 0:55:29 | |
As the vessels burst, | 0:55:36 | 0:55:38 | |
blood cells rush out. | 0:55:38 | 0:55:39 | |
But despite the catastrophic damage, | 0:55:41 | 0:55:44 | |
a repair crew is on the way. | 0:55:44 | 0:55:45 | |
Flowing out with the blood are cell fragments. | 0:55:49 | 0:55:52 | |
Called Platelets, | 0:55:53 | 0:55:55 | |
they are built to stop bleeding. | 0:55:55 | 0:55:57 | |
They gradually form a lattice | 0:55:57 | 0:55:59 | |
that catches the leaking blood cells like a net. | 0:55:59 | 0:56:03 | |
Extra support comes from a stringy protein - fibrin. | 0:56:04 | 0:56:10 | |
Together, they form the clot, | 0:56:10 | 0:56:12 | |
which plugs the hole | 0:56:12 | 0:56:13 | |
and the bleeding stops. | 0:56:13 | 0:56:15 | |
Five hours after the fight, | 0:56:18 | 0:56:20 | |
the effects of the punch | 0:56:20 | 0:56:21 | |
are beginning to show on Johnny's face. | 0:56:21 | 0:56:24 | |
His eye is beginning to swell. | 0:56:27 | 0:56:29 | |
Fluid is flowing into the tissue around the eye. | 0:56:33 | 0:56:38 | |
It's coming from tiny holes in the walls of the blood vessel. | 0:56:38 | 0:56:42 | |
It is a form of defence. | 0:56:45 | 0:56:46 | |
The force of the flow stops any infection in the wound | 0:56:50 | 0:56:54 | |
from travelling into the bloodstream, | 0:56:54 | 0:56:56 | |
trapping it in the tissue instead. | 0:56:56 | 0:56:59 | |
The results of this inflammation are dramatic. | 0:56:59 | 0:57:03 | |
Johnny's eye has now turned a striking shade of purple. | 0:57:05 | 0:57:09 | |
The colour is the product of decaying blood cells | 0:57:18 | 0:57:22 | |
trapped outside the circulatory system, | 0:57:22 | 0:57:24 | |
where they can't survive. | 0:57:24 | 0:57:27 | |
Now Johnny's body starts to clear up the mess. | 0:57:31 | 0:57:35 | |
Macrophages - giant white blood cells - | 0:57:38 | 0:57:41 | |
sweep through the tissue and absorb the dying cells. | 0:57:41 | 0:57:44 | |
Inside the macrophage, | 0:57:46 | 0:57:47 | |
haemoglobin, the chemical that gives red blood cells their unique redness, breaks down. | 0:57:47 | 0:57:53 | |
It's this that gives the bruise | 0:57:53 | 0:57:56 | |
it's familiar cocktail of colours. | 0:57:56 | 0:57:59 | |
As it breaks apart, | 0:57:59 | 0:58:00 | |
haemoglobin transforms into different-coloured chemicals. | 0:58:00 | 0:58:05 | |
Over time, the colour shifts | 0:58:06 | 0:58:09 | |
from green to yellow and finally to brown. | 0:58:09 | 0:58:12 | |
As the Macrophages leave, | 0:58:23 | 0:58:25 | |
they draw the coloured chemicals away from the skin. | 0:58:25 | 0:58:29 | |
Healing is now complete. | 0:58:29 | 0:58:32 | |
Johnny's body has repaired the damage, | 0:58:35 | 0:58:38 | |
just in time for another fight. | 0:58:38 | 0:58:40 | |
Subtitles by Red Bee Media Ltd | 0:58:42 | 0:58:46 | |
E-mail [email protected] | 0:58:46 | 0:58:49 |