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The Great Sperm Race

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    Every day, around
    350,000 babies are born.
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    Each one, utterly unique.
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    A few months ago,
    this baby didn't even exist.
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    And the story of how it came to be
    against impossible odds is extraordinary.
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    This is the moment of conception.
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    When one single sperm
    fused with the mother's egg.
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    If another sperm got there first,
    this baby would be someone else.
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    So what made that winning sperm so special?
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    Why did it succeed over billions of others?
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    To find out, we're going to take you on the epic
    journey sperm undertake through the human body.
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    And we're going to do it by scaling
    the whole thing up to human size.
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    For the first time we'll be able to appreciate
    just what an extraordinary journey sperm face
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    as they try to reach the egg.
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    It's one of nature's
    most spectacular stories
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    and it's the reason you're alive.
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    The sperm will face death at every turn.
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    There is no going back.
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    No surrender.
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    And only one winner!
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    Meet Glenn.
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    Like most average men,
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    Glenn has no idea about
    the miracle of engineering,
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    tucked away in his pants.
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    Glenn's testicles, hanging freely to be 3
    degrees cooler than the rest of his body
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    are producing a thousand
    sperm with every heart beat.
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    And it's this tiny world of phrenetic activity that
    fascinates the world of reproductive science.
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    Sperm are really quite unique because
    they're almost like free living cells,
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    they almost have a life of their own.
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    They have but one aim
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    which is to deliver a genetic
    payload from the male to the female,
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    through a really quite
    complex series of environments,
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    both in the male and in the
    female reproductive tracts.
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    Sperm move all over the place
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    and they like certain things,
    they don't like certain things
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    they're very smart little creatures in a way
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    and they're a lot of fun to watch
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    in the petri dish because
    they're constantly in motion.
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    And the fact that it's occurring
    at the microscopic level
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    means that as scientists we have a great
    deal of difficulty in studying it and observing it.
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    A sperm is just one five hundredth
    of a million millimetre long,
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    so to make things easier,
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    Dr. Allan Pacey and the team of experts
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    have agreed to help us scale up them
    and their world thirty four thousand times.
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    Along the way, they'll
    give us practical advice
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    on how to give sperm the
    best chance of reaching the egg,
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    or what kind of sex to
    have and when to have it
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    to maximise the chances of conception.
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    The first thing we asked
    our experts was quite simple,
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    in our people sized sperm world,
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    what would a testicle be like?
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    The testicle is a, is a roundish
    kind of oblong structure,
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    if we cut it in half, we
    cut thin layers through it
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    and looked at it down a microscope
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    we would see a series of tubules that
    you might liken to floors of a building.
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    If we were to take a sperm
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    and scale it up to man's size
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    you would have to find a building that
    was about a thousand metres cubed,
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    a thousand metres, by a thousand
    metres, by a thousand metres.
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    That done, we can go inside.
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    Waiting in our giant testicle,
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    an army of freshly created sperm.
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    Just like the real thing,
    our sperm are split by gender.
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    Half produce boys and half produce girls.
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    The information needed to
    determine the sex of a baby,
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    is stored in the sperm's head.
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    Here, we find our genetic package,
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    23 chromosomes of DNA
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    including the key gender chromosome,
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    either x for a girl or y for a boy.
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    Situated just below the head,
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    an engine of energy producing mitochondria
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    that propels the sperm's mighty
    tail through the female body.
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    There's many millions of sperm,
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    you could think of that as a
    very, very large office building,
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    where there's lots and lots of elevators
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    and tonnes of people maybe at rush
    hour all moving in different directions.
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    x and y sperm are produced
    in almost equal numbers,
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    boys are thought to be faster
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    but the girls live longer.
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    Once created, each sperm
    ends up in a structure
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    on top of the testicle cord
    called the epididymis.
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    A tightly coiled 6 metre long tube.
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    Which can hold over a billion sperm.
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    Imagine, being crammed into a dark,
    winding 200 mile pipeline with no idea
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    when or if you'll ever get out.
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    It's here, with no inkling
    of the horrors to come.
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    Our sperm must wait.
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    Their fate, now,
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    will depend on events
    unfolding in the outside world.
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    In contrast to the billions of sperm
    produced continuously in Glenn's body.
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    A woman, like Emily will
    produce just one egg per month.
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    Reaching it won't be easy.
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    The battle that sperm have
    in order to find and fertilise an egg,
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    is just immense, everything
    is working against sperm.
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    um, they're not really given a helping
    hand by the female reproductive tract.
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    You've got, hundreds of millions of cells
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    that are swimming wildly about.
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    You've got a lot of death,
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    you've got a lot of obstacles to overcome.
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    They've got to make their way through
    a complex series of environments
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    in a, in a kind of warfare, it is warfare.
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    So if conception is a war,
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    this is the theatre of operations.
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    From a sperm's point of view
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    landing in Emily's vagina is like D-Day.
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    Their first objective, whilst under non stop
    attack from the female immune system,
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    is to reach a tiny opening high
    above them at the back of the vagina,
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    from here, they can enter the cervix.
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    The terrain in the cervix
    is completely different,
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    this, is a dark treacherous
    maze of unchartered tunnels.
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    The sperm will need to find
    a way through to the uterus.
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    One wrong turn and
    it's a slow, lonely death.
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    In the uterus,
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    Glenn's sperm will be looking for a
    doorway just a few sperm head wide
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    in a vast, sterile area, where once again
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    Emily's elite defence force
    will be waiting to take them out.
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    Then it's on to meet the egg,
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    timing is everything,
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    get there a moment too early or too late
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    and your doomed.
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    [Lady's laughter]
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    Emily,
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    Emily,
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    Emily.
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    [Muffled singing]
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    Glenn's sperm are just seconds
    away from participating in
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    one of the most enjoyable experiences
    the human body has to offer.
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    But what would it feel like, to
    be propelled along a narrow pipe
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    covering 50 miles in less than
    2 seconds whether you like it or not.
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    [Dramatic music]
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    For each individual sperm, this is a wet and
    wild high speed one way ticket to oblivion.
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    aaarrrrgggghhhh!!
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    They're not swimming, they're being
    forced there by muscular contractions
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    and by peristaltic contractions.
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    From the point of view from the man,
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    it's a very pleasurable experience.
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    But let's think about it from
    the point of view of the sperm.
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    250 million genetic couriers
    are about to invade Emily's body.
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    Within minutes, most of them will be dead.
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    Millions of Glenn's sperm
    have just entered Emily.
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    They're embarking on an epic
    quest to find and fertilise and egg.
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    aaarrrrgggghhhh!!
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    There can be only one winner,
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    but what chance does an average
    sperm have of succeeding?
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    And is there anything Glenn
    can do to help his sperm along?
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    To find out,
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    we need to look more closely
    at the state of our seed.
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    A ritual men like Dr. Allan Pacey
    have performed on themselves
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    since the invention of the microscope
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    I was in my mid twenties and I was a
    researcher before I plucked up the courage to
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    produce a sample of my own semen
    and have a look down the microscope
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    and I remember the first time
    looking down a microscope
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    and I was just blown away,
    I almost fell off my chair.
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    I remember having to stand up and walk
    around the lab and go back and look down the
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    microscope again and is that, has that really
    come from me, it was just an incredible sight.
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    The incredible sight of the sperm cell
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    was officially discovered in 1677 by a
    Dutchman called Antonie van Leeuwenhoek.
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    The godfather of microbiology, Leeuwenhoek
    built some of the earliest microscopes.
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    Offering him the first, if slightly unclear,
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    image of what he called animalcules
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    which he theorised contained
    the nucleus of a human
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    and had a tail equipped with
    joints, tendons and muscles
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    Later, other early microbiologists believed
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    they could see tiny fully formed
    people stuffed into each sperm head.
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    Modern scientists of course
    have a much clearer view.
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    But they might wish they didn't.
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    Because thanks to the quantity over quality
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    nature of sperm production, a long hard
    look at an average ejaculate today gives
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    us the first clues as to why
    men need so many sperm.
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    Of the many millions of
    sperm that are ejaculated
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    we've got a huge range of different types
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    if we were to look at them
    down the microscope
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    you'd see some sperm that were
    really just hardly moving at all
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    just twitching or some
    sperm that would appear dead
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    and may well indeed be dead.
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    If you looked at their shape, you
    would see sperm with large heads
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    you would see sperm with small heads
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    you may see sperm two heads.
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    In an average fertile man that only,
    18, 19, 20 per cent maximum of his sperm
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    will have a nice size and shape,
    but the rest, the other 80 per cent
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    really aren't going
    to get anywhere at all.
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    To succeed in the race,
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    sperm must be as fresh
    and numerous as possible
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    any old ones won't make
    it past the starting blocks
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    and as they decay they release substances
    that can actually harm younger sperm.
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    What is inappropriate, is the fact that
    the man may be denied by his wife from
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    ejaculating for 3 weeks
    prior to the fertile window in
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    this um, bizarre thought that
    they're going to be super sperm
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    and huge numbers of them,
    that would be the wrong thing to do.
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    So is the right thing to do, to ejaculate
    as often as possible? apparently not.
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    If a man is ejaculating too frequently
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    then the sperm production process and the
    sperm stores simply won't contain enough sperm
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    So, just how regularly should a couple have
    sex to make sure his sperm are match fit?
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    If a couple is having intercourse every
    2 or 3 days throughout the month,
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    then they will hit the fertile window at some
    point and their probability of conception
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    is probably as good as it could be.
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    Now, ready or not
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    Glenn's sperm begin their quest
    for conception in the vagina.
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    Their objective, to find the entrance to the cervix,
    high above them, at the vagina's farthest reaches
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    From the perspective of a sperm the
    vagina is like a vast mountain range.
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    It's an enormous and awe-inspiring place
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    Five miles deep and two miles wide,
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    flanked with vast vaginal walls up to one mile high.
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    Leaving the thick semen armour
    that protected them for landing
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    it's time for Glenn's sperm
    to make a break for the cervix.
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    The great advance has begun.
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    But it's not just the
    epic terrain in the vagina
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    or even their own physical failings that
    now pose a mortal threat to sperm.
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    Everything in the vagina is
    working against sperm survival
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    there's only a matter of minutes
    between sperms arrival and potential death.
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    Sperm face attack from every angle,
    the use of intimate lubricants
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    and even saliva here can render
    sperm lifeless in minutes
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    Worst of all, thanks to the female immune
    system, the vagina is coated with deadly acid.
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    The acid is there to kill and invading force,
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    I think that's a really important point to recognise
    because as far as the female is concerned
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    sperm are an invading force, they're foreign cells,
    they could be there to cause damage
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    they could be there to spread infections,
    they are foreign cells to her
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    and as far as her immune system is
    concerned they need to be destroyed.
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    Within 30 minutes of entering the vagina, over
    99 per cent of sperm will be dead or dying.
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    For our sperm people, it would
    be a scene of devastation.
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    A few million survivors press on
    into the dark side of the vagina.
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    Desperate to somehow escape death by
    reaching the cervix high above them.
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    But the entrance is out of reach,
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    now to avoid total annihilation,
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    Emily's body needs to come to the rescue.
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    To understand how, meet Zita West
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    Zita is a mid-wife who specialises in helping
    couples conceive using natural methods.
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    And she knows the odds of any sperm
    making it past the vagina are slim at best.
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    For most of the month these
    sperm aren't going anywhere
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    you know, the female body isn't allowing them to.
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    Her cervix will be shut and there'll be a plug of mucous
    there that's stopping any sperm getting through.
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    But there will be an opportunity when a lifeline is given
    to enable the sperm to actually reach the egg.
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    And that lifeline is the egg itself.
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    The cervix is usually sealed to protect the
    inside of the body from anything nasty.
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    But as ovulation approaches
    oestrogen surges through the female body
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    causing the body's mucous to
    undergo a radical transformation.
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    So this is what the sperm will be hoping for.
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    It's the same consistency as cervical secretions.
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    And these secretions will be coming
    from the cervix into the vagina
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    forming channels for the sperm to be able to swim up.
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    Now these secretions are alkaline
    and they contain salts and sugars
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    which will nourish the sperm and
    give them energy on their journey.
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    This is the first sort of fitness
    test if you like for the sperm
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    not all the sperm will be able to swim up here, it'll depend
    on the healthiest, the fittest, the fastest swimmers,
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    some that are more abnormal
    in the shapes of their heads etc.
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    won't be able to fit in these channels
    to be able to swim up as easily.
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    Back in our people sized sperm world,
    what would this fitness test compare to?
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    Well, what if your life depended on climbing a ladder?
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    A ladder stretching over a mile into the sky.
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    It's a long gravity defying climb that only
    a tiny fraction of sperm will be able to manage.
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    For the 60,000 or so that do, it's out
    of the frying pan and into the fire.
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    Now they must endure stage 2 of their quest, the cervix.
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    The objective here, to push 4cm to the other side
    and reach the wide open space of the uterus.
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    Sounds simple, until we take a closer look at the terrain.
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    The cervix is quite simply, sperm hell.
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    It's lined with tens of thousands of tiny
    branching tunnels most roads to nowhere
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    and some just a single sperm head wide.
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    With the vast majority, if not all of Glenn's sperm will
    get crushed, trapped and ultimately face a slow death.
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    Nature does have a selection process in the cervix,
    it is selecting sperm that are well made.
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    It would be a bit like me dressed as a sperm,
    trying to climb a staircase that's a kilometre high.
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    I'm defying gravity, I'm going against
    the flow and when I get to the top
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    I find that I've gone down the wrong staircase
    and I should have gone down another one
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    Our sperm must fight their way,
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    crushed amongst thousands of others up through
    a twisted nightmarish urban environment
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    Only one per cent of sperm that make it into the
    cervix have any chance of making it out alive.
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    But could the performance of Glenn's sperm be
    affected by his performance between the sheets?
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    This woman thinks so
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    As Dr Joanna Ellington knows
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    an average fertile healthy couple has just a
    one in five chance of conceiving every month.
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    And for her, success depends on
    the quality of the sex they're having.
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    The better the sex, the better your chance of conception.
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    One of the things a lot of men don't realise
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    is that the more excited they are
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    the further back in the testicle
    they're going to draw on reserves,
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    so if you have, what I like to call 'gourmet sex'
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    where you really spend time and you
    really make it fun for both partners
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    that is going to make the man more excited, more
    stimulated and he's going to ejaculate more sperm
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    and they're healthier sperm.
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    Research shows that men enjoying 'gourmet sex'
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    can ejaculate up to fifty per cent more sperm.
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    Good news for Glenn, but what about Emily?
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    Could more fun in bed for her
    help the chances of conception?
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    Nineteen century evolutionary psychologists believed
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    'the purpose of female organisms was to
    keep a woman lying down longer after sex
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    keeping sperm in the body and
    increasing her probability of conception.'
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    More recently its been suggested the female orgasm
    evolved to create a stronger bond between lovers
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    increasing the chances of the couple
    staying together after a child is born.
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    Nice theories,
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    but there's never been any actual
    evidence to support the idea
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    that female orgasm had any functional
    relevance what so ever, until now.
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    I happen to be a fan of female orgasm myself, and that's
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    from a physiological stand point
    as well as the personal one.
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    What happens during female orgasm is the
    pH in the vagina actually is elevated some,
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    there's some changes in the ion concentration
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    and there are contractions that help
    pull the sperm up into the female's body.
  • 28:07 - 28:12
    Strangely this remarkable theory has been supported
    by a Danish study into the sex lives of pigs.
  • 28:12 - 28:16
    Creatures with reproductive systems
    almost identical to ours.
  • 28:16 - 28:21
    We don't know if a pigs having an orgasm or not
    but we know that if we stimulate their clitoris
  • 28:21 - 28:26
    when they do artificial insemination
    we can increase pregnancy rates.
  • 28:26 - 28:32
    Some people mistakenly think that female orgasm is bad
    for conception and there's certainly no evidence of that
  • 28:32 - 28:36
    in fact the evidence would suggest
    that it's a good thing to have.
  • 28:41 - 28:42
    Luckily for Glenn,
  • 28:42 - 28:47
    three thousand of his sperm are both full
    fit and manage to avoid getting lost.
  • 28:51 - 28:56
    But as the female immune system
    prepares to mobilise its elite assassins,
  • 28:56 - 29:00
    the great sperm race is about to get even tougher.
  • 29:20 - 29:22
    Inside an unsuspecting woman,
  • 29:22 - 29:25
    the great sperm race is underway.
  • 29:26 - 29:30
    Our army of sperm, unstoppable
    by sheer force of numbers
  • 29:30 - 29:34
    have fought their way through the
    mountainous terrain of the vagina
  • 29:34 - 29:37
    and squeezed through the tight
    passage ways of the cervix.
  • 29:42 - 29:49
    Getting this far has cost many lives,
    now just three thousand sperm remain.
  • 29:51 - 29:52
    The adventure continues,
  • 29:52 - 29:55
    thanks largely due to the fact that Emily is ovulating.
  • 29:56 - 29:58
    So is it a coincidence
  • 29:58 - 30:04
    this couple had sex at the perfect moment during her most fertile and sperm friendly monthly period?
  • 30:09 - 30:11
    This man doesn't think so.
  • 30:11 - 30:13
    For evolutionary psychologist Geoffrey Miller
  • 30:13 - 30:17
    nothing in the great sperm race happens by accident.
  • 30:17 - 30:23
    The sperm didn't get there by chance the woman's
    body and brain has arranged for it to be there.
  • 30:23 - 30:30
    Its made choices, in its life and its mate search
    and its discrimination between male partners
  • 30:30 - 30:33
    and its sexual behaviour that
    led to the sperm being there.
  • 30:33 - 30:36
    Female choice runs evolution, largely
  • 30:38 - 30:42
    Unlike men, who can produce
    millions of sperm every day,
  • 30:42 - 30:47
    women are born with all the eggs
    they will ever have, about a million.
  • 30:47 - 30:50
    By menopause that number has fallen to zero,
  • 30:50 - 30:53
    making them the most important
    commodity in the natural world.
  • 30:54 - 30:59
    A fertile egg from a healthy and intelligent egg
    donor costs about $30,000 on the open market.
  • 30:59 - 31:05
    If you take the size of the egg that adds out to
    about a thousand trillion dollars per pound.
  • 31:06 - 31:11
    So even in strictly economic terms a fertile egg,
    it's rare, it's special, it's valuable
  • 31:13 - 31:16
    Each egg is made even more precious
  • 31:16 - 31:19
    because one will appear for just a few days per month.
  • 31:19 - 31:24
    Many female animals make the most
    of ovulation by experiencing oestrous,
  • 31:24 - 31:30
    where their physical appearance, scent and
    behaviour will change to advertise their fertility.
  • 31:33 - 31:36
    Geoffrey Miller believes woman do the same thing.
  • 31:37 - 31:41
    It used to be thought that humans uniquely lost oestrous
  • 31:41 - 31:44
    that human females don't go
    into oestrous when they ovulate.
  • 31:44 - 31:49
    That somehow we have this
    pair bond that trumps oestrous,
  • 31:49 - 31:54
    but in fact the new research is showing
    human females do go through oestrous,
  • 31:54 - 31:58
    it serves exactly the same functions
    that it does for other mammals,
  • 31:58 - 32:02
    all the same hormones all the same
    psychology is still right there
  • 32:02 - 32:05
    under the surface of human culture.
  • 32:08 - 32:11
    So could women effectively go on heat every month?
  • 32:12 - 32:18
    Could their reproductive systems be unconsciously
    controlling their actions and men's responses?
  • 32:22 - 32:24
    Miller believes so
  • 32:24 - 32:29
    and to prove it he and his team at the university of New
    Mexico have carried out some extraordinary research
  • 32:30 - 32:32
    at a gentleman's club
  • 32:39 - 32:43
    We know that lap dancers earnings fluctuate a lot,
  • 32:43 - 32:47
    so it seemed like an ideal
    set-up for being able to ask them,
  • 32:47 - 32:51
    how much have you earned night by nightshift by shift?
  • 32:51 - 32:55
    and to be able to track that in relation to
    where they are in the menstrual cycle.
  • 32:55 - 33:02
    And we thought that was a pretty cool way of,
    of, quantifying female attractiveness to males
  • 33:05 - 33:10
    The dancers provided Miller's team with information
    about their earnings and menstrual cycles
  • 33:10 - 33:13
    over a period of 300 work shifts.
  • 33:13 - 33:17
    The equivalent of about 5,000 lap
    dancers for their male customers.
  • 33:19 - 33:21
    The results were surprisingly strong,
  • 33:21 - 33:24
    I was amazed at how strong the effects were
  • 33:24 - 33:31
    that the women in oestrous were earning about twice as
    much as they were earning when they were mensturating.
  • 33:31 - 33:34
    If your'e ovulating you're a lot more attractive to men,
  • 33:34 - 33:39
    you're earning higher tips, you're
    getting called over for more lap dances.
  • 33:44 - 33:48
    Miller's research suggests a link between
    female ovulation and attractiveness to men.
  • 33:49 - 33:52
    But if women are unconsciously
    controlling men's actions once a month,
  • 33:53 - 33:55
    What actually happens?
  • 33:56 - 34:01
    They're more sexually perceptive,
    higher sex drive more interest in sex,
  • 34:01 - 34:04
    they dress in more stylish and revealing clothing,
  • 34:04 - 34:07
    their voice pitch gets more attractive to men,
  • 34:07 - 34:10
    breasts become more symmetrical,
  • 34:10 - 34:15
    um, the waist to hip ratio changes,
    so the waist gets relatively thinner.
  • 34:15 - 34:21
    There also changes in smell, so that the women's scent
    will be become more attractive to men during oestrous.
  • 34:24 - 34:30
    So with a little help from the unconscious power of
    ovulation the great sperm race continues.
  • 34:34 - 34:39
    Two hundred and fifty million of Glenn's
    battling sperm entered the vagina.
  • 34:39 - 34:43
    Just three thousand have made it through
    the dark twisted hell of the cervix.
  • 34:44 - 34:48
    Which now opens out into an
    environment that is altogether different.
  • 34:53 - 34:56
    Our sperm expert Dr. Allan Pacey knows,
  • 34:57 - 35:03
    if you or I were a sperm entering
    the uterus would be quite a sight.
  • 35:23 - 35:27
    From a sperm's point of view the
    uterus represents a vast plain
  • 35:27 - 35:31
    across which they have to navigate and find at the other end
  • 35:31 - 35:35
    actually quite a tiny opening that will lead
    them through to the fallopian tubes.
  • 35:38 - 35:44
    Scaled up to sperm people size the uterus
    becomes a large area of open country side,
  • 35:44 - 35:48
    two miles long and around half a mile wide.
  • 35:53 - 35:57
    For our sperm finding the entrance to the fallopian tubes
  • 35:57 - 36:02
    just a few sperm head wide is like
    looking for a needle in a haystack.
  • 36:05 - 36:09
    Once again it's ovulation to the rescue.
  • 36:12 - 36:16
    Ovulation occurs on one side one month,
    the other side another month.
  • 36:16 - 36:23
    So on the times that the egg is going to
    be ovulated from the ovary on the left,
  • 36:23 - 36:27
    the uterus seems to preferentially
    move material to the left hand side.
  • 36:27 - 36:33
    So the sperm are probably carried to a large
    degree by these muscular contractions
  • 36:33 - 36:37
    and moved through the uterus relatively quickly.
  • 36:49 - 36:52
    But on this journey nothing is ever that easy.
  • 37:02 - 37:06
    Glenn's sperm are about to discover they're not alone.
  • 37:09 - 37:12
    They're running straight into an ambush.
  • 37:13 - 37:19
    The primary function of the uterus is of course to receive
    the developing embryo should conception occur
  • 37:19 - 37:23
    and to gestate the foetus throughout pregnancy.
  • 37:23 - 37:26
    It's not really designed for sperm,
    it's designed for something else
  • 37:26 - 37:30
    it will almost certainly begin to contain leukocytes
  • 37:30 - 37:33
    and the immune response will be
    mounted to try and mop up sperm
  • 37:33 - 37:36
    and to try and kill the sperm before
    they get to the fallopian tubes
  • 37:39 - 37:43
    Leukocytes are the assassins of the female body,
  • 37:43 - 37:46
    blood cells commanded into
    action by the immune system.
  • 37:46 - 37:50
    Massing into the uterus in their
    thousands with murderous intent.
  • 37:50 - 37:53
    In comparison to sperm, leukocytes are quite large,
  • 37:53 - 37:58
    they're big cells, they often hunt in
    packs they will detect a sperm
  • 37:58 - 38:05
    and many leukocytes will descend upon the sperm
    and encapsulate it and dismantle it slowly.
  • 38:05 - 38:10
    For the female body of course, lukocytes
    are wonderful essential things,
  • 38:10 - 38:13
    fighting disease and harmful foreign materials.
  • 38:14 - 38:18
    But let's try to imagine them from the
    perspective of a trespassing sperm.
  • 39:33 - 39:36
    Once again Glenn's sperm face utter decimation,
  • 39:38 - 39:42
    as thousands are killed by Emily's immune system.
  • 39:48 - 39:52
    Just a few dozen lucky ones reach
    the entrance to the fallopian tubes.
  • 39:57 - 40:00
    Only to find that there is a strict door policy.
  • 40:02 - 40:06
    Sperm have to display the
    correct swimming characteristics
  • 40:06 - 40:09
    in order to get through that uterotubal junction.
  • 40:09 - 40:14
    And any sperm expressing a very random
    form of motion is probably excluded.
  • 40:16 - 40:20
    There's also potentially a molecular
    recognition system there
  • 40:20 - 40:25
    so only sperm that are expressing the right
    molecules actually are allowed through.
  • 40:41 - 40:45
    Sperm have faced death and
    destruction in the uterine cavity,
  • 40:45 - 40:49
    the leukocytes have been trying to,
    ah, kill them along the way
  • 40:49 - 40:54
    and only a lucky few in comparison to the
    many millions that are ejaculated initially
  • 40:54 - 40:59
    actually make it into the fallopian tubes
    where finally they get to sperm heaven.
  • 41:24 - 41:27
    Welcome to one of Emily's fallopian tubes.
  • 41:28 - 41:33
    10cm of what can only be
    described as paradise for sperm.
  • 41:51 - 41:56
    The environment of the fallopian tube
    is just very accommodating for sperm,
  • 41:56 - 42:02
    it's what sperm have been aiming for and it's set-up to
    try and maintain sperm health and they can have a rest.
  • 42:04 - 42:07
    Its got nutrients for them, its got the right pH
  • 42:07 - 42:15
    it has the right ion concentration and some of these
    sperm will actually bind to the fallopian tube cells
  • 42:15 - 42:18
    their membranes will become very closely associated
  • 42:18 - 42:24
    so that the fallopian tube cells can pass
    nutrients and sugar and protect those sperm.
  • 42:25 - 42:29
    Scientists believe with no immune
    system trying to kill them
  • 42:29 - 42:34
    sperm can blissfully hang around in the
    fallopian tubes for hours, even days
  • 42:34 - 42:37
    but ultimately it's hard to know for sure.
  • 42:40 - 42:45
    At the farthest reaches of the reproductive tract
    the fallopian tubes are very difficult to study,
  • 42:45 - 42:50
    so difficult in fact some scientists
    are willing to extraordinary lengths.
  • 42:51 - 42:54
    When I was done having children
    I choose to have my tubes tied
  • 42:54 - 42:57
    and I told my Dr. that I wanted to do an experiment
  • 42:57 - 43:01
    where I had intercourse before I had the surgery
  • 43:01 - 43:06
    and then she was to cut out that section of my
    fallopian tubes where the sperm were stored
  • 43:06 - 43:11
    so that I could look at them under the electron
    microscope and count how many sperm were there.
  • 43:11 - 43:15
    So it was pretty humorous actually because I'm
    coming out of anaesthesia and I was like
  • 43:15 - 43:19
    did you get it, did you get it?
    cause no one had ever done this before.
  • 43:21 - 43:25
    There were about twenty sperm
    in my tubes, that we counted.
  • 43:27 - 43:29
    Thanks to such dedication,
  • 43:29 - 43:34
    we now have a clearer sense of what happens
    during the final stage of the voyage to the egg.
  • 43:38 - 43:42
    The sperms objective, to wait for the
    egg to appear ahead of them
  • 43:42 - 43:48
    find it, swim through its outer layer and be the
    first to reach its inner core and seal victory.
  • 43:50 - 43:53
    But how will they know when the egg
    has been released from its follicle?
  • 43:54 - 43:57
    We're just beginning to
    understand that there is receptors
  • 43:57 - 44:00
    that communicate between the egg and the sperm
  • 44:00 - 44:04
    and the sperm smell the egg,
    they're able to sense where that egg is
  • 44:04 - 44:07
    and you can even see this some in the petri dish
  • 44:07 - 44:09
    when you're doing in vitro fertilisation
  • 44:09 - 44:14
    if you put an egg in there, boy those sperm just
    right away they orient themselves towards that egg
  • 44:14 - 44:18
    they're going right towards it, they're
    not wandering aimlessly around the dish
  • 44:18 - 44:23
    hoping to encounter it, it's not left up to chance,
    they know what they want to go find.
  • 44:25 - 44:28
    It's believed sperm wait in the fallopian tubes
  • 44:28 - 44:31
    until they pick up an irresistible sense signal
  • 44:31 - 44:33
    which intensifies as the egg draws near.
  • 44:36 - 44:41
    One study has shown, the scent attracting the
    sperm smells just like Lily of the Valley perfume.
  • 44:42 - 44:46
    The egg basically lays out a
    red carpet and asks the sperm
  • 44:46 - 44:50
    this way, this is where you want to go,
    this is the end of your journey.
  • 44:50 - 44:53
    So instead of swimming backwards into the uterus
  • 44:53 - 44:56
    they head straight up that fallopian tube, right to the egg
  • 44:56 - 45:00
    and that's how that final step of the sperm race is won.
  • 45:05 - 45:08
    Back in the scaled up world of our great sperm race
  • 45:08 - 45:13
    an egg is finally released, making its way
    towards one end of the fallopian tube.
  • 45:15 - 45:18
    The finish line is tantalisingly close.
  • 45:19 - 45:22
    And from here on in timing is everything.
  • 45:41 - 45:46
    She has no idea, but Emily could be
    just minutes away from being pregnant.
  • 45:49 - 45:53
    Beating incredible odds, Glenn's sperm
    have fought their way through her body
  • 45:53 - 45:56
    and have reached one of her fallopian tubes
  • 45:56 - 45:59
    where hopefully an egg will be waiting.
  • 46:01 - 46:04
    Just single figures have made it this far,
  • 46:04 - 46:08
    scaled up to people size, what happens next?
  • 46:10 - 46:15
    Imagine an olympic freestyle swimming final,
    where the winner gains immortality
  • 46:15 - 46:18
    and the rest are killed.
  • 46:23 - 46:28
    Scent signals released during ovulation
    will make the sperm hyperactive
  • 46:28 - 46:31
    giving them the ability to actually fertilise the egg,
  • 46:31 - 46:35
    shedding layers of proteins,
    in a process called capacitation.
  • 46:46 - 46:49
    Up until now they have been
    swimming in quite straight lines
  • 46:49 - 46:53
    but now they're swimming becomes much more erratic.
  • 46:53 - 47:00
    And that tail beat will give them power and propulsion
    in order to get through the outer coat of the egg.
  • 47:08 - 47:12
    All of a sudden they are a hundred per cent on target.
  • 47:18 - 47:23
    They want to find that egg, they want to penetrate
    that egg and it's a race for the finish.
  • 47:27 - 47:30
    So once they capacitate,
    sperm die within just a few hours,
  • 47:30 - 47:33
    so it's a no going back.
  • 47:37 - 47:42
    On the sperm people scale, the egg
    drifts just a mile or so ahead.
  • 47:42 - 47:45
    But as our reproductive scientists can testify
  • 47:45 - 47:51
    the egg's 24 hour lifespan will present
    the sperm with one final, fatal hurdle.
  • 47:51 - 47:57
    What needs to be kept in mind
    for this whole great sperm race
  • 47:57 - 48:05
    is timing, timing, timing, timing
    because the egg has a limited lifetime.
  • 48:10 - 48:16
    What if the egg arrives a little earlier?, we want some
    sperm to be able to capacitate relatively early.
  • 48:16 - 48:20
    What if that egg comes, maybe a few
    hours from now or another day?
  • 48:20 - 48:25
    Well, you don't want all the sperm to be capacitated right
    at the beginning because then they're going to die.
  • 48:52 - 48:55
    Having arrived hours before the egg,
  • 48:55 - 49:01
    these sperm reach the end of the line
    falling into the abyss beyond the fallopian tubes.
  • 49:07 - 49:10
    Behind them, just two heroic sperm remain,
  • 49:10 - 49:13
    all that survives of a quarter of a billion.
  • 49:14 - 49:20
    These two are y chromosome bearing male sperm
    and an x chromosome female
  • 49:20 - 49:23
    left Glenn's testicles 14 hours ago.
  • 49:32 - 49:37
    They've endured an incredible journey
    and against overwhelming odds
  • 49:37 - 49:41
    they've got their timing, just right.
  • 49:45 - 49:48
    At the farthest reaches of Emily's reproductive system
  • 49:48 - 49:52
    the egg is waiting.
  • 49:58 - 50:05
    If you or I were a sperm, the egg would soar
    into the sky as high as Nelson's column.
  • 50:06 - 50:09
    During the great sperm race, there's
    been this great attrition of sperm
  • 50:09 - 50:12
    from the point of ejaculation through to the fallopian tube.
  • 50:12 - 50:16
    Actually at the site of fertilisation
    when the egg is being fertilised
  • 50:16 - 50:19
    there may only be one sperm,
    there may be two or three,
  • 50:19 - 50:24
    but only very few sperm are actually
    fighting for that final prize.
  • 51:01 - 51:06
    Eventually one sperm will hit the outer coat of the egg
  • 51:06 - 51:09
    and this is it, this is the moment
    that they've been waiting for.
  • 51:12 - 51:18
    To secure victory, all this sperm has to
    do now is find a way inside
  • 51:19 - 51:22
    The sperm is carrying this, this genetic payload
  • 51:22 - 51:29
    for delivery, but that genetic payload
    has to be able to get into the egg.
  • 51:30 - 51:35
    And the way that it gets into the egg
    is the sperm literally blows its top.
  • 51:35 - 51:40
    Above the head of the sperm, there's kind
    of a bag of juices, a bag of enzymes
  • 51:40 - 51:42
    that are really important at this stage
    of the process
  • 51:42 - 51:51
    by touching an egg that bag bursts and those enzymes
    will facilitate the sperm and finally penetrating through,
  • 51:51 - 51:53
    um the outer coat of the egg,
  • 52:10 - 52:13
    The great sperm race has been won.
  • 52:19 - 52:23
    The victorious male sperm is instantly devoured
  • 52:23 - 52:29
    as Glenn's genetic information
    merges with Emily's waiting DNA.
  • 52:42 - 52:48
    So you get this elegant dance of male chromosomes
    and female chromosomes coming together
  • 52:48 - 52:54
    which will officially announce the fact that, that egg
    is fertilised and that new life is being created
  • 52:54 - 52:58
    and development of a new individual
    has started.
  • 52:58 - 53:00
    Just fourteen hours ago,
  • 53:00 - 53:05
    hundreds of millions of sperm embarked on the
    most incredible adventure in the natural world,
  • 53:05 - 53:08
    an adventure that claimed all their lives.
  • 53:14 - 53:17
    So what made that winning sperm special?
  • 53:17 - 53:20
    Why did it succeed over billions of others?
  • 53:22 - 53:26
    When you think about the odds that
    any single one of us are here right now
  • 53:26 - 53:31
    compared to the hundreds and millions of other
    sperm that in that ejaculate that were left behind
  • 53:31 - 53:35
    there could have been, a smarter offspring
  • 53:35 - 53:38
    a handsome or more athletic, a better in every way
  • 53:38 - 53:44
    ones that just didn't make it, because they either
    weren't in the right place at the right time
  • 53:44 - 53:49
    or you know they just didn't find their way
    through the cervix or uterotubal junction
  • 53:49 - 53:52
    or maybe they capacitated a little too
    early before the egg got there
  • 53:52 - 53:55
    or maybe they were a little too late to capacitate
  • 53:55 - 54:03
    so there's just a lot of luck involved with it as
    well as to which sperm actually is able to fertilise.
  • 54:08 - 54:11
    Yet one unremarkable sperm,
  • 54:11 - 54:15
    against odds of trillions to one did not die in vein,
  • 54:17 - 54:23
    it has given its life to start an utterly unique new one.
Title:
The Great Sperm Race
Video Language:
English
Duration:
55:29

English subtitles

Revisions