PBS Nova The Miracle of Life 1983 revised

Description

[MUSIC]

The following film, The Miracle of Life,

is about the process
of human reproduction.

Please use discretion when
choosing to view the program.

4.5 billion years ago the young planet
earth was a mass of cosmic dust and

particles.

It was almost completely engulfed
by the shallow primordial seas.

Powerful winds gathered random
molecules from the atmosphere.

Some were deposited in the seas.

Tides and
currents swept the molecules together.

And somewhere in this ancient
ocean the miracle of life began.

[MUSIC]

The first organized form of
primitive life was a tiny protozoan.

[MUSIC]

Millions of protozoa
populated the ancient seas.

[MUSIC]

These early organisms were completely
self-sufficient in their sea water world.

[MUSIC]

They moved about their aquatic
environment, feeding on bacteria and

other organisms.

[MUSIC]

They were covered with hundreds of
tiny whipping hairs called cilia and

flagella that made movement possible.

[MUSIC]

From these one-celled organisms
evolved all life on earth.

[MUSIC]

And the foundation of life, the cell,
has endured unchanged since

the first tiny organisms swam
in the cradle of life, the sea.

Every living being is made up of cells,
the basic units of life on earth.

[MUSIC]

And all cells reproduce themselves by
dividing into two identical cells.

[MUSIC]

This is a single body cell
from a human being, and

this is the process by
which all cells reproduce.

Now there are two cells,
each exactly like the parent.

In the cell's nucleus is
the extraordinary chemical substance DNA.

The DNA is contained in 46 chromosomes
in every cell of the human body.

Each chromosome, in turn,
is made up of thousands of genes,

discrete segments of DNA which
lie along the chromosome.

Penetrating even deeper into
the structure of the chromosome,

we see the DNA molecules themselves.

DNA contains all the genetic
information of the cell, and

it is the only living substance
capable of reproducing itself exactly.

Without DNA, duplication and
therefore life itself is not possible.

All DNA in all living organisms
is chemically identical, but

its arrangement in genes and chromosomes
determines what the cells will become.

Here a tiny primitive organism,
the protozoan,

a massive complex mammal the elephant.

[MUSIC]

A palm tree, swaying in the tropical
breeze, or a human being.

[MUSIC]

We are about to witness, for the first
time, a wondrous and complex process,

[MUSIC]

The actual conception and
growth of a new human being.

[MUSIC]

Each beginning lies deep inside
the mother's body in the ovaries.

[MUSIC]

Each ovary contains a quarter
of a million egg cells,

which reach full development even
before the woman herself was born.

The eggs each contain 23 chromosomes,

the mother's genetic contribution
to her future offspring.

During each menstrual cycle,
the ovaries produce hormones

which stimulate the growth of
a single one of these eggs.

At the midpoint of her cycle,
the follicle,

which encloses the egg in its
protective layers, ruptures.

This is ovulation.

The egg travels through the fallopian
tube, which connects the ovary and

the uterus, or womb.

In the tube, the egg waits for
sperm from the father to fertilize it.

The fertilized egg,
now with genetic material from

both parents,
moves through the tube to the uterus,

where it attaches itself to
the nutrient rich lining.

And here the ovary itself.

[MUSIC]

In cross-section, stained blue for
better visibility,

we see the hundreds of tiny egg cells.

[MUSIC]

This one is nearly mature and
is surrounded by its nutritive layers.

When it is fully developed, the follicle
which encloses the egg will swell,

like this one, with fluid,
the liquor folliculi.

[MUSIC]

Inside the follicle, the egg and
its nutritive layers floats

in this water of life which has
the same salt content as the sea.

[MUSIC]

The swollen follicle here on
the left is then gently brushed

by the swaying fimbriae, the outermost
fringes of the fallopian tube.

[MUSIC]

These fringes are activated by
the hormones just before ovulation.

[MUSIC]

They sweep over the surface of the ovary
searching for the newly released egg.

As ovulation nears,
the fringes become filled with blood.

[MUSIC]

The follicle at the center
is about to burst.

Directly above the white reflections,

the liquor folliculi pours
out of the follicle.

Concealed somewhere within it, is the egg.

[MUSIC]

The fringes search for
the newly released egg.

It lies here surrounded by a cloud
of its own nutritive cells.

It is only the size of a grain of sand.

[MUSIC]

At the far right,
the egg is drawn into the fallopian tube.

[MUSIC]

Deep inside the egg is
the nucleus of new life itself.

[MUSIC]

This is the mouth of the fallopian tube.

[MUSIC]

Its almost imperceptible muscle
contractions move the egg along toward

the uterus.

[MUSIC]

Here, the egg has reached
the interior of the tube itself.

[MUSIC]

These many forms of tissue are lined with
tiny cilia which maintain a constant,

gentle motion that draws
the egg along its length.

[MUSIC]

The inside of the tube
is actually only about

twice the thickness of
a single human hair.

[MUSIC]

It takes the egg three to four days to
travel this distance of only five inches.

[MUSIC]

The translucent egg here lies in a muscle
fold deep inside the fallopian tube

[MUSIC]

On the diagonal edge below the egg,
we can see a thin shimmering

layer of the cilia which line the tube,
gently moving the egg along.

They are exactly like the cilia
of the primitive protozoa.

The egg must join with a sperm within
24 hours of leaving the ovary for

conception to take place.

If no sperm are present
the egg disintegrates and

the same cycle will happen
again the following month and

throughout all the women's
childbearing years.

This remarkable cycle is made possible
by complex molecules, the sex hormones.

[MUSIC]

Crystallized and stained,
they look like this.

[MUSIC]

Hormones control a woman's
entire reproductive cycle.

[MUSIC]

Hormones control a man's
reproductive ability as well.

[MUSIC]

Only seven weeks after conception,
the fetal system is

permanently sensitized to be male or
female by the sex hormones.

[MUSIC]

One fetus will develop ovaries, and

its brain will be programmed to release
hormones in cycles, it is female.

Another fetus will develop testicles,
and its brain will

release constant low level amounts
of sex hormones, it is male.

[MUSIC]

77 billion human beings
have lived on this planet.

Four billion live here now.

And every year,
128 million new ones are born.

We have already seen part of the woman's
remarkable contribution to this

unending process.

Now we will explore the man's.

During a man's lifetime,
his testicles produce billions of sperm.

They are stored here in the epididymis.

The Cowper's gland produces a lubricating
fluid to aid the sperm's journey.

The prostate gland secretes an alkaline
fluid to protect the sperm.

Together they produce most
of the fluid called semen.

During ejaculation the sperm
leave the epididymis,

moving through the vas deferens,
this tube in the body cavity.

They approach the seminal vesicles
which release a solution of sugar

to nourish them.

Cowper's and prostate fluids combine
with the sperm and the blended

semen continues out of the man's body
through the urethra in the penis.

[SOUND] This is the interior

of the urethra itself.

We are travelling up into the man's
body from the outside through the penis.

The red areas are blood vessels.

The black spots are calcium deposits.

In reality, the journey is only seven or
eight inches long.

[SOUND].

Ahead, the red area is
the opening to the bladder.

During sexual arousal, a valve here
stops urine from entering the urethra.

The valve is now open.

[MUSIC]

Here, near the bladder,

the urethra passes through
the prostate gland.

The walls of the prostate have
more than 30 orifices, like these,

which squeeze out prostate fluid
when sperm pass through the urethra.

It is about the size of a golf ball,
and it resembles a sponge.

[MUSIC]

Inside, it is filled with the small
cavities which produce the fluid.

[MUSIC]

These are the testicles, highly magnified
and without their usual protective pouch.

Unlike the ovaries,

their counterpart in women,
the testicles lie outside the body cavity.

They are made up of the tightly
coiled seminiferous tubules,

which have a total length of 700 feet.

In the tubules, sperm are produced
at the extraordinary rate

of 100 million every 24 hours.

In the tissue between the tubules,
the sex hormone testosterone is produced.

The testicles are the essential
male organs of reproduction.

They function well only under
very specific conditions.

One of these specific
conditions is temperature.

Sperm are produced most
efficiently at several

degrees below normal body temperature.

These images from a thermal camera
reveal the various temperature zones

in the scrotum, the pouch of skin in
which the testicles are suspended.

The white areas are the warmest,
and the green ones, the coolest.

The scrotum keeps the testicles
away from the body's heat.

This is a cross section of one
of the tubules in the testicles,

stained blue and magnified 2,000 times.

At the dense center of the tubule
is the transport canal,

which carries mature sperm away
to the epididymis for storage.

The smaller compartments produce many
new immature sperm every 36 hours.

As the sperm become more mature,
they move closer to the central canal.

The average man produces over 400 billion
sperm in his reproductive lifetime.

These sperm, magnified 4000 times,
have been in production for

approximately a month.

They are tightly packed in the tubule
within the testicle, their heads and

tails intertwined.

[MUSIC]

Inside the developing sperm heads,

the normal body cell's 46
chromosomes have been reduced to 23.

But this reduction of chromosomes, so

essential to future reproduction of the
species, puts the sperm in mortal danger.

The man's body considers
these cells enemies.

But the sperm are defended by nurse cells,

like this one and
the large cell at the right.

They form special protective barriers
around the maturing sperm cells.

Each nurse cell cares for
many sperm at a time.

This tendril is part of the remarkable
communication network which connects

each nurse cell to over 150 separate
sperm cells throughout the tubule.

The tendrils enable the nurse cells to
feed and protect the maturing sperm.

And to move them closer
to the transport canal.

This sperm is nearly mature.

During its development, it has lain
in total passivity in the tubal,

being protected and
nourished by the nurse cell.

When mature,

like this one, it is transported by
the nurse cell to the epididymis.

Millions of sperm are stored in
these densely packed tubules, which,

if stretched out,
would be 15 or 20 feet long.

[MUSIC]

The mature sperm in the epididymus
will pass out of the man's

body through ejaculation 2
to 300 million at a time.

[MUSIC]

Or they will eventually die and
be reabsorbed.

These sperm carry the man's genetic
material, and they are fully mature.

[MUSIC]

But they are not yet
able to fertilize a woman's egg.

They do not obtain that ability until
they are actually far up inside

the woman's body.

[MUSIC]

They may stay in the epididymis,
the bag-like structure on the left, for

several weeks.

[MUSIC]

While here,
they develop the ability to swim.

A sperm propels itself by means
of a long tail, a flagellum,

which lashes vigorously from side to side.

This extraordinary activity has but
a single purpose, to deliver the genetic

material in the sperm's head quickly and
precisely to the woman's egg.

On the tip of the sperm's head is a layer
of enzymes and enzyme inhibitors.

The inhibitors preserve the enzymes

which will be needed later to
penetrate the surface of the egg.

This is how the sperm's head
looks without its enzyme cap.

The material of the head itself
is loaded with the actual genetic

information which will be
transmitted to the egg.

These are the strands of DNA which
will be transformed into chromosomes.

This is one of the many fuel packets
arranged along the mid-piece of the sperm.

The fuel consists of sugars,
Which is converted into energy for

the sperm's locomotion.

The propulsion system of the sperm's
tail is made up of a bundle of cords or

filaments.

The filaments are covered
with thousands of tiny hooks.

As the hooks intermesh,
the whole bundle begins to bend, and

the tails of the sperm begin
to whip around like this.

It is a primitive but
highly efficient system of propulsion.

The system does not function
perfectly every time.

On the average, up to 20% of
a normal man's sperm are deformed or

imperfect in some way.

Perhaps, one reason why a man produces so
very many sperm is that so

very many things can go wrong
with the sperm themselves.

They may have two tails, like this one.

Some even have three tails.

In another common deformity the heads of
these sperm appear to be nearly severed

from their tails.

This sperm has been attacked by bacteria.

And this one may have been
produced too rapidly.

It will never complete its development.

White blood corpuscles,

the large round cells are often
found together with defective sperm.

Their presence indicates the likelihood of
infection, fever, or even a common cold.

Most of these sperm deformities could have
been caused by just a slight elevation in

the temperature of the testicles.

Environmental conditions too
often damage sperm production.

Over crowding.

Stress.

Smoking.

Chemical pollution of air and water.

Occupational hazards.

Radiation.

Poor nutrition.

All part of modern life.

Even our modern clothing may
affect sperm production.

Tight blue jeans, for example,
hold the testicles up close to the bod,

perhaps raising their temperature
those few critical degrees.

But in spite of such obstacles,

human beings have been successfully
reproducing for millions of years.

Since the first organisms swam in the sea,
the cycle of life has been continuous,

fueled by the need and
the drive to reproduce.

[MUSIC]

Among human beings,

that drive is intimately linked
with attraction and desire.

[MUSIC]

Affection and

romantic love may initiate the dense
of culture which may lead to conception

[MUSIC]

Sexuality, affection,

and tenderness can all be part of

the complex rituals of mating.

[MUSIC]

But desire and physical love
possess a silent language all

their own that signal parter's
readiness to each other.

The eyes are part of that silent language.

Visual impressions stimulate and

excite special nerve cells in
the sexual areas throughout the body.

The skin too,
is part of the silent language.

It is amazingly sensitive and
responsive to the touch.

It contains millions of these sensory
receptors which when stimulated

direct messages of sexual
arousal to the brain.

Many of these are concentrated in
the body's most responsive areas,

the erogenous zones.

One of these, the man's penis,
is densely packed with sensory receptors.

Here, seen at enormous magnification.

They relay messages of sexual
stimulation to the brain,

which triggers the complex sequence
of events leading up to ejaculation.

The length of the penis is made of many
small cavities called erectile tissue.

When a man is sexually aroused,
the signals from the brain cause these

erectile tissues to become
engorged with blood.

As we can see in these images
from the thermal camera,

the sudden flow of blood to
the penis raises its temperature.

The man's blood pressure,
heartbeat, and respiration increase.

And the blood causes the penis to
become erect and elongated, so

that sperm can be most easily
delivered to the woman's egg.

In the epididymis the hundreds of
millions of waiting sperm which will

soon be expelled from the man's
body accumulate in a mass.

As sexual arousal reaches its peak,
the entire male sexual system

must function perfectly for
ejaculation to take place.

Cowper's gland.

Prostate.

Seminal vesicles.

And epididymis.

This is the actual journey
made by the sperm.

At the climax of sexual arousal
the man's nervous system triggers rapid

involuntary contractions of the muscles
in the walls of the epididymis.

These propel the sperm up into the man's
body along this tunnel like tube,

the vas deferens.

The sperm themselves travel the distance,

a little over 12 inches
in only a few seconds.

The seminal

vesicles release nourishing fructose,

which blends with
the sperm as they pass by.

They mix with the prostate fluid.

The blended semen approaches the urethra.

Its total volume is actually
about one-half a teaspoon.

This is the last leg of the journey.

The semen containing the sperm is
forced out through the penis by

the man's muscle contractions.

[SOUND] And at last, it is ejaculated

into the woman's vagina.

[MUSIC]

As the semen enters the woman's body,
it immediately slows down and coagulates.

[MUSIC]

Perhaps it becomes thicker to ensure that
most of the sperm stay within the vagina.

Or perhaps,
the coagulation is a kind of defense, for

the environment in the vagina
is extremely acid.

[MUSIC]

The acidity protects the woman
against bacteria and infections,

but it is also dangerously
inhospitable to the sperm.

Nearly one quarter of them
will die almost immediately.

[MUSIC]

About 20 minutes after ejaculation,
the semen becomes fluid again.

The surviving sperm
become vigorously active,

swimming rapidly against the downward
currents in the woman's body.

[SOUND] There is great urgency,
for the sperm will remain viable,

able to fertilize for only 28 to 48 hours.

[SOUND] This is the sound made

by thousands of active sperm.

[SOUND] The sperms'

great activity has but

one goal, to find and

fertilize the egg.

There are so many of them that
success might seem assured, but

the barriers too are numerous.

[MUSIC]

The high percentage of defective
sperm has already lowered the odds.

[MUSIC]

So has the vagina's
hostile acid environment.

[MUSIC]

And the woman's own defense
system attacks the sperm.

They are unwelcome cells from another
organism and they are potential enemies.

[MUSIC]

Her defense cells aggressively protect
her from the invaders by destroying them.

[MUSIC]

The sperm are programmed to seek the egg,
but

some of them try to fertilize
the first round object they find.

In this case, an ordinary body cell.

[MUSIC]

Still, in spite of the obstacles,

hundreds of thousands of sperm make their
way up through the vagina to the cervix,

the mouth of the uterus, which will
lead to the Fallopian tubes and the egg.

[MUSIC]

The cervix secretes strands of
a special fluid protein called mucin.

[MUSIC]

During ovulation, it is very liquid and
easy for the sperm to swim in.

[MUSIC]

The strands of mucin provide tiny
channels less than 1/100th of

a millimeter wide, directing
the sperm closer to their objective.

[MUSIC]

But many of them never find the strands of
mucin, and they will die in the vagina.

[MUSIC]

Those that survive will swim up
the mucin channels towards the uterus.

[MUSIC]

They swim in dense bunches.

[MUSIC]

The outer ones may protect the inner
ones from the woman's acidity and

defense systems.

[MUSIC]

Once inside the cervix,
the sperm continue on their journey.

Some remain here, perhaps to provide
a backup for those that continue on.

[MUSIC]

The rest proceed up through the cavity
of the uterus in search of the egg.

[MUSIC]

Their number is noticeably reduced.

[MUSIC]

Here, from inside the uterus, we see
the openings to the two Fallopian tubes.

[MUSIC]

The sperm swim toward them.

[MUSIC]

One leads to the waiting egg,
the other to an empty tube.

[MUSIC]

Only half of the few remaining sperm will
swim up the tube which holds the egg.

[MUSIC]

The tubes are lined with millions
of tiny cilia, the same cilia which

helped draw the egg from the ovary
toward the uterus at ovulation.

These cilia sway constantly,

creating a gentle downward current
that the sperm must swim against.

[MUSIC]

Some sperm gets stuck in among
the cells lining the walls of the tube.

[MUSIC]

Others lose their sense of direction.

[MUSIC]

During this part of the sperms' journey,

the layer of enzyme inhibitors at the tips
of their heads is slowly being worn away.

The sperm are fully capacitated and
able to fertilize the egg.

If they ever

encounter it.

Of the 200 million sperm that
begin this long journey,

only about 50 every reach the egg.

[MUSIC]

The egg is surrounded by two
layers of the nutritive cells,

which have nourished on its
journey in the Fallopian tube.

[MUSIC]

The sperm immediately release their
digestive enzymes to break through

these protective nutritive layers
in order to reach the egg itself.

[MUSIC]

At best, only one will eventually
enter and fertilize the egg.

[MUSIC]

A joint force of their
exertions starts the egg

rolling around like
a mysterious celestial body.

[MUSIC]

All the while the sperm are dissolving
their way through the egg's outer layers.

[SOUND].

The first sperm to reach the egg's
membrane is immediately drawn inside.

This is the tail of the penetrating sperm,

seen from the surface of the egg
at enormous magnification.

And this is a picture from
inside the egg itself.

It has been fertilized now for
only a fraction of a second.

Here is the penetrating sperm with a
circle around it from a wider perspective.

Only the single sperm will
be allowed inside the egg.

A rapid biochemical change took
place in the egg's membrane.

It is now impermeable to all other sperm.

Once inside, the sperm, too,
undergoes a dramatic transformation.

It loses its mid piece and tail.

The tailless head swells up
almost like rising bread.

This hole in the sperm heads covering is
the first indication that it is about

to rupture and
release its precious genetic material.

Here, the first strand of genes is making
its way out of the sperm into the egg.

The genetic material continues
to spill out of the sperm head.

Its tightly packed molecules contain
the father's hereditary message.

They almost seem to have been
dispersed by an explosive force.

This is an extreme close up of
the genetic material itself.

The magnification on the television
screen is over half a million times.

[MUSIC]

The genetic material of the mother's
egg and the father's sperm combine.

Two cells have joined to make a single

new cell, and within 24 hours,

that new cell begins to divide.

These early cell divisions of the human
embryo have never been filmed.

[MUSIC]

The fertilized egg now has two nuclei,

the small indentations at
the center of the cell.

The first division of the egg

is beginning.

[MUSIC]

Now there are two identical cells,

still within the same nourishing
material of the original egg.

No growth has occurred, but
rather a distinction between cells.

Once it has began to divide,
the fertilized egg is called a zygote.

[MUSIC]

Now, there are four cells.

[MUSIC]

The divisions happen at such
an accelerated pace, that there's little

opportunity for the new cells to
grow before they divide again.

[MUSIC]

Now, there are eight cells.

[MUSIC]

Each new generation of cells in the zygote
is smaller than the one before it.

[MUSIC]

Another division and another.

[MUSIC]

As the zygote divides,
it moves along the tube toward the uterus.

Now, it has become a dense,
compact cluster of many cells.

[MUSIC]

And after five days it
is called a blastocyst.

It is still no bigger
than the original egg.

Its center is filled with liquid.

[MUSIC]

[MUSIC]

Within ten days of fertilization,

the blastocyst implants itself
firmly in the lining of the uterus.

Already, the mother's hormones are
directing changes in her body to prepare

it to support the growing embryo.

[MUSIC]

Barely visible to the naked eye,

the embryo will be nourished by the lining
of the uterus, and then by the placenta.

[MUSIC]

After two weeks, the embryo is elongated.

It is barely one-tenth of an inch long

[MUSIC]

At the top,
what will become it's head and brain.

[MUSIC]

Below at the tail, the embryo is
firmly attached to the placenta,

which will nourish it.

[MUSIC]

At four weeks, the embryo has arm buds and
is distinctly curled.

[MUSIC]

It has the beginning of eyes.

[MUSIC]

At five weeks the nose
begins to take shape.

[MUSIC]

At six weeks leg buds are apparent.

The embryo is less than half an inch long.

It floats inside
the fluid-filled amniotic sac.

It's spine is clearly visible.

[MUSIC]

At seven weeks, the embryo is
three-quarters of an inch long.

[MUSIC]

It can move its hands, on which
there are clearly defined fingers.

[MUSIC]

Its internal organs are visible.

[MUSIC]

The eye lenses are formed.

[MUSIC]

The skull bones, rich in blood vessels,

are growing together at an angle
at the crown of the head.

[MUSIC]

At eight weeks,
the fingers of the hands are well defined,

and the toe joints of
the feet are clearly visible.

[MUSIC]

At about ten weeks,
the embryo is considered a fetus.

It can move actively.

There is a suggestion of an ear.

It is two inches long and
it still has the stump of a tail.

[MUSIC]

At 11 weeks it is 2.5 inches long.

[MUSIC]

At 12 weeks, 3 inches long.

[MUSIC]

Here, the umbilical cord,
connecting the fetus to its food supply.

[MUSIC]

By 14 weeks, it can bring its
hands together and suck its thumb.

[MUSIC]

By 15 weeks, the sensory organs
are nearly completely formed.

[MUSIC]

And by 16 weeks,
it is actively turning inside the mother.

[MUSIC]

This fetus is 18 weeks old.

It is 5.5 inches long, and is here shown
15 times larger than its actual size.

[MUSIC]

Its mouth and lips are fully formed, and

it has the strange nasal plugs whose
purpose is not yet understood.

The eyes of the fetus are closed,
but it can see.

[SOUND] This sound is made by the fetus as

it breathes in the amniotic fluid in

what is known as fetal respiration.

It brings the fluid in through its mouth,

and then breathes it out again.

[SOUND] The umbilical cord is the fetuses

link to it's source of life, the mother.

[SOUND] Here are the fetus' sex organs.

[SOUND] All its important
physiological systems have developed,

but it will be at least another
eight weeks before the fetus

has even a remote chance of
surviving outside its mother's womb.

[SOUND] Whatever signals

the beginning of birth

is still a mystery.

But when the fetus is ready to be born,
the uterus begins its powerful

contractions and
the process of birth begins.