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Embryological & Fetal Development

  • An overview of development: fertilization, embryological development (cleavage, blastula formation, gastrulation, embryonic growth), fetal development, postnatal development (infanthood, childhood, adolescence), puberty, maturity
  • Fertilization occurs when a secondary oocyte (ovum) fuses with a spermatozoan (sperm), forming a zygote
  • The oocyte is subsequently activated after fertilization to prevent further sperm from entering and to start the development
  • Repeated cleavage (cell divisions) result in a blastula
  • The blastula implants itself into the endometrium of the uterus
  • The blastula eventually becomes a gastrula, forming 3 main layers: ectoderm, mesoderm, and endoderm
  • Extraembryonic membranes include: yolk sac, amnion, allantois, and the chorion
  • The placenta eventually forms to connect the mother’s blood supply to the embryo/fetus, which receives nutrients/gases through the umbilical cord
  • In an early embryo, the forebrain, eyes, pharyngeal arches, arm buds, leg buds, and a tail are visible (under a microscope)
  • Ultrasound involves high frequency sound waves projected into the uterus to detect possible developmental issues and to figure out the sex of the baby in utero
  • The embryo is called a fetus before the end of the first trimester and pregnancy is supposed to last 40 weeks
  • Labor includes these stages: dilation, expulsion and delivery
  • Delivery problems/procedures include: episiotomy, breech birth, caesarian section (C-section), premature delivery, and conjoined twins
  • Did you know…
    • Q: In the lesson you mentioned that people with Down syndrome can live normal lives, but I know a 40-year-old person in my neighborhood with Down syndrome who still lives/depends on his parents. What did you mean?
    • A: What I meant is that though Down syndrome presents a lot of mental difficulties and developmental problems, the severity and level of adversity is variable. Decades ago, doctors would commonly tell pregnant women with a Down syndrome fetus that their child would not be able to do anything on its own and they would use the term “retarded” to describe him or her. These days you can find some people with Down syndrome employed, getting driver’s licenses, and other independent adult activities. Yes, it typically takes a lot longer for someone with Down syndrome to learn a new skill, but they have the potential to do a lot.

Embryological & Fetal Development

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Development Overview 0:05
    • Fertilization
    • Embryological Development
    • Fetal Development
    • Postnatal Development
    • Maturity
  • Fertilization Overview 1:39
    • 23 Chromosomes
    • Occurs a Day After Ovulation
    • Forms a Zygote
  • Oocyte Activation 4:33
    • Block of Polyspermy
    • Completion of Meiosis II
    • Activation of Enzymes That Increase Metabolism
    • Only Nucleus of Sperm Moves Into Oocyte Center
  • Cleavage 8:14
    • Day 0
    • Day 1
    • Day 2
    • Day 3
    • Day 4
    • Day 6
  • Implantation 11:03
    • Day 8
    • Initial Implantation
    • Lacunae
    • Fingerlike Villi
  • Gastrulation 12:39
    • Day 12
    • Ectoderm
    • Mesoderm
    • Endoderm
  • Extraembryonic Membranes 16:17
    • Yolk Sac
    • Amnion
    • Allantois
    • Chorion
  • Placenta 19:28
    • Week 5
    • Decidua Basalis
    • Cavity
    • Umbilical Cord
  • Week 4 Embryo 23:01
    • Forebrain
    • Eye
    • Heart
    • Pharyngeal Arches
    • Arm and Leg Buds
    • Tail
  • Week 8 Embryo 26:33
  • Week 12 Fetus 27:36
  • Ultrasound 28:26
    • Image of the Fetus
    • Sex Can Be Detected
  • Week 40 Fetus 29:46
  • Labor 31:10
    • False Labor
    • True Labor
    • Dilation
    • Expulsion
    • Delivery
  • Delivery Problems 33:57
    • Episiotomy
    • Breech Birth
    • Caesarian Section
    • Premature Delivery
    • Conjoined Twins
  • Embryological Conditions / Disorders 40:00
    • Gestational Trophoblastic Neoplasia
    • Miscarriage
    • Induced Abortions
    • Ectopic Pregnancy
    • In Vitro Fertilization
    • Amniocentesis
    • Birth Defects

Transcription: Embryological & Fetal Development

Hi and welcome back to

This is the lesson on embryological and fetal development.0002

Overview of development from conception up to adulthood would go like this.0005

It starts with fertilization.0012

That is the moment of conception when a sperm fuse with egg you are going to get what is called a zygote.0014

That is the first cell of life.0020

From that point on it is embryological development until it becomes a fetus.0022

The first step in getting from zygote to embryo is called cleavage.0027

That is a term for when cells physically divide the cytoplasm and separate.0033

Cleavage happens after telephase if you took biology recently.0039

The cleavage happens over and over, you form a ball of cells and that ball of cells has a hollow center is called blastula.0045

It goes to what is called gas relation.0055

Gas relation is a folding in and then you get defined layers within that ball of cells.0058

You will get outer layers of cells, middle layers of cells, inner layers of cells.0064

There is this gastro development until we call an embryo.0067

It is called embryo until about week 9 and from that point on it is a fetus.0071

It is a fetus in through the second trimester, third trimester, and eventually birth happens.0077

You have post natal development.0084

Here this cute baby is going to develop into a toddler, a child, adolescence, and adulthood 0086

and eventually reach maturity then you die.0095

Fertilization overview, how does fertilization actually occur?0097

What are the details?0104

It is a fusion of the secondary oocyte and a spermatozoa.0104

Secondary oocyte if you saw the female reproductive system lesson that comes from what is called a oogonium.0112

That is like the stem cell that makes eggs and the secondary oocyte is more technical term rather just calling it an egg or an ovum.0120

This is actually not completely done with meiosis.0128

I will cover that a little bit in the future lesson.0132

Once the sperm makes contact with it, it will finish meiosis and become that full fledged ovum.0134

Each of these should have 23 chromosomes that is the haploid number that is chromosomes without a pair the go with those chromosomes.0143

When you have sperm coming together you have 23 going with 23 chromosomes and that is how you get the diploid number 46 once again.0153

The volume ratio when you compare the oocyte and the spermatocyte or spermatozoan is about 2,000 to 1 volume wise.0161

The amazing thing is that when you take 1 sperm and stretch out with its little sperm head 0172

and flagellum it is close to about half the length of the diameter of an egg cell.0178

But the volume is crazy different 2,000 times the volume in an egg.0184

It makes sense because besides the sperm head having a nucleus there is not much else going on there.0190

When you look inside of an ovum or one of those egg cells you have got a lot of cytoplasm 0196

outside of the nucleus but contain from the plasma membrane.0202

All the major organelles that you are going to have in that ball of cells and that embryo come from mom including mitochondria, ER, golgi, etc.0205

Those are a lot of what are called the epigenetic factors just things other than DNA that are inherited from the maternal side.0216

Fertilization typically occurs within a day after ovulation in the fallopian tube.0224

What happens within a day after ovulation, the part of the fallopian tube that is going to happen here is infundibulum.0229

If you remember the fallopian tubes have those fimbrae that is closer to the ovary rather than close to the uterus.0234

If fertilization happens where the sperm reach the egg in the second day after ovulation even the third day 0241

then the egg will have gotten closer to the body of uterus.0250

A zygote is a term for the first cell of a new life and that zygote should have 46 chromosomes if all is well.0254

Here is a little micro graph of the surface of an egg cell and the sperm.0265

Oocyte activation, once a sperm actually come into contact with the egg you are going to have some things happen that are important in a sequence.0271

A series of events that are triggered when the plasma membranes of sperm and oocyte come into contact with each other.0285

First thing that happens is a block to polyspermy.0291

Here is what that means, it is a fancy way of saying the egg hardens its exterior so that no other sperm can penetrate once that first one is gone through.0296

When you look at a bunch of sperm trying to penetrate an egg you have this region on the very outside 0305

that actually would not be broken down unless a lot of sperm are poking at it.0313

All of their achrosomes in and you are going to see what an achrosome is later on in this lesson.0320

But all of those little enzymes sacs or the edges of the sperm heads where way out of the area and you will get to what is called the zona placeta.0324

Once a single sperm penetrates the zona placeta there is an immediate chemical reaction that hardens the outside 0334

because you do not want multiple sperm entering rather 1 egg.0342

You want the diploid number.0347

You want 46 chromosomes.0348

You do not want 92.0350

You do not want 4 copies of every chromosome.0351

That is not going to be a viable human being.0355

Block of polyspermy makes sure that only 1 sperm head has actually entered the egg cell.0358

Completion of meiosis 2.0365

A secondary oocyte is not quite a full fledged ovum.0368

It is actually arrested in meiosis 2.0375

Meiosis 2 completes once that sperm has entered and then also the activation of enzymes and that increases metabolism.0379

In an egg cell you have a lot of MRNA or messenger RNA strands that are just hanging out in the cytoplasm.0390

They are kept inactive by certain proteins.0397

Once the oocyte is activated by the sperm entering you turn on the MRNA 0400

and you start synthesizing a lot of important proteins that are part of making an embryo.0405

Those things are on hold until it needs to start it.0410

Once you have that diploid number, once those chromosomes have come together in that zygote 0414

it is time to get a catabolism going because there is going to be a lot of cell divisions.0419

Only the nucleus of the sperm is supposed to move into the center of the oocyte.0423

You got that middle piece of the sperm and hear more about later in this lesson.0427

The flagellum those things do not stick around and a lot of times they fall off right after the sperm has come in.0431

The egg has the potential to destroy those things.0440

If for some reason paternal or the dad side mitochondria stay around in the egg and not destroyed, 0443

that actual results in a severe disorder that has a lot of impact on your muscle tissue.0452

Healthy individuals do not have paternal mitochondria.0458

All of mitochondria that men and women have to be from their mother and that is because those mitochondria or 0463

in the cytoplasm of the egg cell and the ones from the sperm they just got the sperm to that destination.0471

They do not stick around typically.0477

This is actually a micrograph of an oocyte.0479

They have removed some of the outer cells the trophoblast cells that you are going to hear more about later so you can get a better view of it.0483

But that is an oocyte.0490

Cleavage means that it is this pinching in.0498

Let us go through what happens day by day basis.0501

Day 0, meaning that is the day that fertilization happen.0505

You get the first cleavage of division and then by the time days gone by you got 2 cells.0509

The amazing thing is when we go through all this all the way up to blastula or ball of cells, the size does not change.0517

That is the amazing thing early on is that you have this large ovum and then all the cell divisions happen maintained in that space 0525

you do not get a drastic increase in volume not quite yet.0533

Even we get to the point where there is 80 something cells, it is taking up the same space we had at day 0 when there is a zygote.0537

Day 1, 2 cells divide and make 4 cells.0546

Eventually you get to point day 3 where they say it is an early morula.0550

A morula is a dense ball of cells.0556

Day 4, more cell divisions have happened then we have an advance morula.0559

A little bit more cells taking up that space.0565

Fast forward to almost a week into this day 6 we finally have what is called a blastocyst or blastula it was another name for it.0568

That what is we are looking at right here.0576

This little picture is a hollow ball of cells with a nourishing layer called trophoblast.0578

Number 4 hear, what you are looking at is an inner mass of cells.0583

I am going to highlight that in yellow.0588

Inner cell mass that is what is going to become the embryo, these cells right here.0590

You will see what is going to happen to those later on in this lesson.0595

Number 3/2, you are looking at the trophoblast layer around the outside of this.0598

That is a nourishing body for this very young life.0605

Eventually this trophoblast will not be needed eventually because it will be connected to the mother's blood supply but not quite yet.0610

This particular blastocyst or blastula has not anchored itself into the endometrial lining of the uterus.0618

Eventually you got the placenta coming out of that and the umbilical cord.0625

That is not quite yet.0628

Number 1 is called the blastocels.0630

That is a funny spelling but that is how it spells.0633

That is the hollow section here.0645

We will see that even when we get to the folding in you will still see this hollow section.0647

We have a blastula rolling down the fallopian tubes and into the uterus, into the cavity of the body of the uterus.0653

Implantations, this blactocyst is going to implant itself in the endometrium of the uterus.0662

This usually begins at around day 8.0670

It could be day 9 but day 8 usually. 0672

Enzyme is secreted by the trophoblast, that outer layer into the endometrial lining allowing the initial implantations.0675

It can kind penetrate those outer layers of the endometrium.0682

Lacunae are little holes or channels that help to supply nutrients to the developing trophoblast from the blood supply of the endometrium.0686

There are these finger like villi, they look like little finger projections extending from the trophoblast into the endometrium.0696

These continue to develop to start suck nutrients in this area.0705

I should rephrase that.0710

Initially what happens is diffusion.0712

It is diffusion of nutrients.0715

It is not really sucking into the trophoblast region but diffusion is a passive process 0717

and there is a lot of blood flow from the mother into the endometrium.0723

You are going to see in the next few slides this is very important.0728

The blood cells that developed in this very early new life, those blood cells if you lookup at the 0732

hemoglobin of the fetal blood cells actually they have a higher affinity for oxygen than the maternal blood cells0739

meaning that the baby’s early red blood cells are even more of a magnet for oxygen than the mother's red blood cells.0745

That is going to be a very important piece of the puzzle in terms of how this works.0753

After this blastocyst implanted itself further development happens within that inner mass of cells.0758

By day 12 the inner cells of the blastocyst had developed into 3 distinct germ layers.0767

Germ here do not think of bacteria, think of like the word germination like in plants 0773

in terms of a seed developing in coming to be in terms of it making new life.0780

German in a sense that it is like a germination.0787

There are 3 distinct germ layers.0790

The ectoderm, mesoderm, and endoderm.0795

Ecto means outer, meso means middle, endo means inner.0798

Given some examples here of what these cells become in a fully develop baby or human being that we can recognize.0803

This is not all of the tissues.0810

You can look up everything that the ectoderm becomes and whatever the endoderm becomes.0813

These are some major parts.0817

The way they know this is by studying gas relation.0819

Gas relation is the development of the embryo and fetus.0824

If you tag certain cells with certain chemicals and those chemicals remained in the tissues that develop later on, 0827

you know that those tissues are descendants from that particular cells that you tagged.0836

They do this to animals a lot over the years.0842

Ectoderm that outer layer that you see here in blue becomes the epidermis, the outer layers of skin.0845

Neural tissue, the brain nerves, everything, skeleton.0852

Mesoderm I do not see that in this particular drawing but when this folding in happens from the blastula 0855

you do get like another folding in from this green area.0863

It almost looks like little ears. 0867

That folding in this section here and here is what gives you the mesoderm.0869

Mesoderm forms slightly deeper levels of skin like the dermis.0874

The muscles come from the mesoderm and your heart and blood vessels come from the mesoderm.0879

Finally the innermost part next to this cavity, this space here they call the blastopore.0884

Archenteron is the term for this.0892

The blastopore is just the opening into the archenteron.0895

The endoderm you get the digestive tract glands and a lot of different glands and the urinary system.0898

The way I remember that is the endoderm, the digestive tract is if you think of the inside the body the most inner holes, 0905

the most inner cavities inside your body, the digestive system comes to mind.0913

You have this pathway going all through your body from mouth to anus and the most inner passageways 0916

that stuff is moving through it is easier to think that is the digestive tract.0924

It is funny this blastopore we know in humans and animals, vertebrates especially, or animals with spines, 0927

this blastopore is the first hole that we see in this gas relation that becomes the anus.0937

In other animals if you look at insects the blastopore becomes the mouth.0945

Later on in our development you are going to see the mouth hole development.0951

Blastopore becomes the exit for the digestive tract so it is no surprise that this greenish layer of cells gives rise to the digestive tract.0956

Gas relation, the forming of gastrula is that folding in and establishment of germ layers that become a major tissues of the body.0965

When we look at what happens to the trophoblasts, those surrounding nourishing cells they 0976

become different extra embryonic membranes or membranes outside of the embryo itself.0982

Yolk sac is one of them.0987

This is an interesting thing.0989

We are not birds and reptiles that are born inside of this egg where you need the yolk sac to nourish you.0990

The yolk sac evolution of biologists assume that this yolk sac is from our ancestors.1000

Mammals came from a class of reptiles and we are mammals.1008

Yolk sac it is not filled with yolk.1014

This does not actually contain yolk that you would see in a chicken egg but it is the sac that helps give rise to our blood cells 1017

that eventually receive oxygen specifically from the mother through that connection of the placenta.1026

The yolk sac once the placenta is established and umbilical cord comes to be the yolk sac is off to the side of the umbilical cord itself.1038

The amnion, have you heard the amniotic fluid.1047

The amnion is being this fluid filled region that surrounds the embryo, protecting it, you are going to get cells from embryos sloughed off into it.1050

The baby swallows amniotic fluid.1060

This is a fluid filled region that surrounds the embryo and there is the amniotic sac that contains the amniotic fluid.1064

As a baby develops it expands.1071

By the time you are into the 2nd trimester the amniotic sac has expanded a great deal 1073

and eventually is pushing up against the inner edge of the uterus, the endometrium.1078

The allantois when I first saw this as a student this is allantoa.1084

The allantois is this little area that eventually gives rise to the urinary bladder and parts of this have to do 1089

with the establishment of that connection for nourishment and gases to the mother.1100

The chorion you see this term chorionic villi associated with chorion.1106

This leads to the entrance of blood vessels feeding the gastrula.1111

Before we have a full fledged placenta you have what are called chorionic villi.1115

By the time you are into week 3 in the first month of development before women typically know that they are pregnant, 1121

you have chorionic villi that are helping to get on blood vessels from the endometrial lining to feed the baby.1128

At a certain point the trophoblast is not enough.1138

The trophoblast initially nourishes that ball of cells but once it grows in the point where it is thousands and thousands of cells 1141

you need a lot more entrance of nourishment and gases from the mother.1148

Chorionic villi has a lot to do with that.1153

There is a test you can do later on pregnancy called chorionic villi sampling and 1155

this is the tissue that they can get a sample of test for certain kinds of problems that could be happening with these.1160

The placenta initially blood supply to the embryo enters to chorionic villi.1167

Initially we would not call that a placenta but the chorionic villi and those arise from the allantois, 1175

the allantoic arteries and veins help that blood connection happen.1183

By week 5, if you are going in with a camera and look around you would see a placenta.1188

And from that point on the placenta is there it grows a little bit as time goes on to help the growing baby.1195

A full fledge placenta has some major layers I want to introduce you to.1204

The decidua bacillus this is a basal layer and decidua means a falling off like deciduous trees.1208

If you are wondering what is falling off thing?1215

Look here, this is a little image from Gray's Anatomy.1218

Here is the endometrium if you are wondering what we are looking at.1222

This whole thing here is the placenta and here is the umbilical cord.1226

It is anchored to the endometrium of the uterus and usually it is towards the top near the fundus of the uterus 1230

towards the top of the body or superior portion of the body of uterus.1241

If the placenta is down too low in the cervix that could lead to some problems specially during labor.1245

The deciduous part here why do they call them those?1252

The decidua you see here there is little like breaks in this blood vessels and blood is entering this space.1256

That is what this is referring to that this layer here, parts of the maternal tissues that have blood flow 1263

there is kind of a wearing away to the point where maternal blood just pours into this cavity.1273

That is why of I have said there is a cavity in here.1279

All of the space here.1287

You could see here it is the inter villi space.1288

You can barely see that term but this space around the chorionic villi 1291

which are coming from the embryo you have maternal blood just coming into here.1295

That is brilliant because you think of the chorionic villi is like little blood vessel branches, little blood vessel trees in a sense.1300

As long as you have maternal blood adjacent to it diffusion will bring those oxygen gases, the nutrients into the blood flow of the baby.1310

What also happens is the waste from the baby enters into this cavity and can go back into the mother.1322

The carbon dioxide being generated in the baby's body and the waste products from metabolism go the reverse way.1330

The umbilical cord that is right here.1336

It is cut off you do not see the full thing but the umbilical cord goes into the belly button region 1341

what does become the belly button after the umbilical cord falls off when babies are born.1347

The umbilical cord has arteries and veins.1353

Arteries going into the baby and veins going back to the mother.1357

Here is the placental body.1361

When birth happens the placenta comes out they call it the after birth because after the baby comes out 1364

the baby has umbilical cord attached to it, it is the other end of the umbilical cord in the placenta.1370

Once the baby is born there is no need for the placenta anymore that comes out after the baby.1375

Week 4, embryo by the time gas relation happened and these different areas of that folded ball of cells become parts that you can actually notice.1382

This does not quite like human but you can see some parts that are going to be more obviously human several weeks later.1395

If we look at embryos of rabbits, cows, dogs they look very similar to human embryos at this point in time.1404

Let me show you some these different parts.1413

The forebrain which becomes the majority of the higher brain that is right here.1415

The forebrain is in this region.1421

The eye I think you can probably notice the eye already at week 4 right there.1424

The heart is right in this region.1438

The pharyngeal arches what are they?1441

The pharynx is the throat.1453

The amazing thing is that even in human embryo you would see these little folding looking like 1455

they could become gills but they do not because we are human.1461

This is one of those as far as I know this vestibular structure of a leftover remnant from ancestors in the ocean from 100,000,000 years ago.1464

Even reptiles you can trace their ancestry back to vertebrates in the water that breath with gills.1474

Pharyngeal arches you would see them for a little while and then they do not develop into gills 1483

because we have lungs and we do not breathe underwater.1489

Arm and leg buds I am going to highlight those in yellow.1492

Arm and leg bud that is the cool thing is on you will see little knobs popping out where the arms and legs are going to be.1496

If you fast forward for a few weeks later you would see a longer bud that looks like little paddle for the hand with no fingers.1512

The way that you get the fingers developing is imagine that I have no spaces here and this is all filled in with skin and tissue.1519

What happens is this region is stimulated to die, this region is stimulated to die, the cells signals that you are done.1527

It is called apoptosis that is basically programmed cell suicide or cell death.1534

If that does not happen completely you would be born with webbed hands or feet.1541

There are places in an embryo where cells need to stop developing to create spaces.1547

And then tail, we actually do have a tail for a while as an embryo here and you can see that.1552

This of course is going to become the spinal column.1560

You can even see already little divisions between sections of what is going to become vertebrae.1563

The reason why the tail does not look like a tail later on is the amount of growth in this part of the embryo 1571

compared other parts gradually lessens so that it does not become a long tail.1578

We grow into that tailbone and ends up being not visible outside the buttocks region.1583

Week 8 embryo, about 2 months of the process this is bigger in real life the size of a week 8 embryo is about that big.1592

This is typically before a woman is showing before you can know she is a pregnant.1606

It is that big just a few centimeters that inch of long.1612

This baby the reason why we have this image is because it could have been a spontaneous abortion.1617

The baby was lost and this tissue was preserved probably through the process of plastenation 1624

which is where you can preserve tissues in a deceased body or organ from a deceased person.1630

You can see a very early umbilical cord and how enters into the body.1636

You can see it is about 8 or 9 weeks, 38mm or 3.8cm.1642

You are close to 1 or 1½ inch.1650

Week 12 fetus, by the end of the first trimester, the first approximate 3 months, the rudimentary parts of all major organ systems have formed.1655

The heart is beating, the brain has brain function, there is a liver, there are lungs, are all of these ready for the outside world.1668

No, the earlier the baby is born prematurely the less developed the organs are.1679

I am going to talk more about premature births in terms of the danger of that.1687

But you can see with an ultrasound here that this is a human being.1691

Ultrasound has gotten better and better over time.1697

They are not all black and white and grainy anymore.1701

There some good 3 dimensional images from ultrasounds.1703

Speaking of ultrasounds how does it work?1706

Ultrasound is named after the high frequency sound waves that are used and projected into the uterus and the reverberation gives an image of the fetus.1709

The reason why even in sound waves we can hear them is that the frequency of the sound waves is beyond human hearing, tens of thousands of hertz.1720

Sex can be detected between 18 and 22 weeks.1732

It depends.1736

But potential birth defects or other problems are also observed.1738

Ultrasounds are not just for telling of mom and dad that is a boy or a girl.1741

Seeing the baby how it is moving, how the body parts look can the ultrasound technician or doctor if there are some other problems.1745

Technicians look for obvious genitalia markers to determine sex.1757

At this point in time when you are around the 20 week marker so you can look at the genital region 1767

and see whether not there is a labia majora. 1774

You can see whether not there is an early penis with the testicular region.1777

Fast forward, week 40 fetus.1788

That is a full term birth happens at week 40.1791

I was actually closer to 41, I came a little bit later than was expected.1796

But you know plenty of births happening at week 38 or 39.1802

Week 40 this is an older image of how the baby is situated.1808

A normal presentation meaning normal orientation of the fetus prior to birth is at the head is facing down towards the cervix, the birth canal.1813

You can see that the mother’s organs are pressed against a great deal, the intestines, the liver, a lot of different areas are being pushed aside.1825

This is one the reasons that later on pregnancy a pregnant woman has to go in the bathroom a lot because the bladders being pressed upon.1835

The colon and the intestines are being pressed upon.1844

Also the stretching of all these materials can stretch out.1848

The sphincters that keep those things where it is supposed to be.1852

By week 40, pregnant woman feeling a lot of extra mass there and probably going to the bathroom a lot more.1856

We will move onto how does labor happen?1864

Prior to week 40 some will experience false labor.1869

These are little bits of contractions in the uterine muscles that do not need lead to real labor and real birth.1875

Sometimes it will be like week 35 or 36 a woman will feel stuff going on down there, go to the hospital and it is a false alarm.1884

The baby is not ready to come out yet.1896

True labor is when biochemical and mechanical factors reach the point of no return.1897

The unconscious portions of a female brain have signaled it is time.1902

This baby is ready.1910

Labor contractions are what tell you it is true labor.1911

We are talking initially there are 3 stages initially.1915

It is dilation and what is dilating is the cervix.1920

The cervix is that bottom part, most inferior part of the uterus and when it starts dilating 1924

it starts gradually opening so that the baby can start to come through the birth canal.1930

Initially you are going to get contractions that last about ½ minute and may happen every 10 to 30 minutes.1936

That is the beginning of it.1946

That is when it is time to go to the hospital.1947

Accompanied with the dilation usually they say the water broke.1949

What they are talking about is the amniotic sac itself inside the uterus has broken.1953

The sac itself has a hole in it and amniotic fluid comes out.1959

That is a sign that the baby is coming.1963

If the amniotic sac gets a hole in it prior to dilation.1966

The danger that is if now there is a hole in the amniotic sac where the baby is but there is no labor that puts the baby at risk of infection.1971

Now that protected area is open but the baby is hanging in there still.1979

They sometimes will actually forced labor to happen.1985

There are certain drugs to make labor pains happen and to give the baby out as soon as possible.1989

Typically associated with dilation is that water breaking.1995

Next up is expulsion that is where there are significant contractions of the uterine muscles.2000

We are talking those labor pains lasting longer period of time and happening every few minutes.2008

That means that the baby is going to be expelled out.2014

This can sometimes just be 1 or 2 hours and can last a lot longer in some women.2018

The end result of expulsion is delivery of the baby.2026

This is when the baby is actually exited the birth canal.2030

It is actually born.2035

Here are some delivery problems or issues that can come up.2037

Episiotomy is if the baby coming to the birth canal is too much for the birth canal opening for the vagina opening to bear.2041

Instead of risking a tearing of the perinium meaning the tissue next to the vaginal opening, 2053

instead of having that tearing the doctor will make incisions in that region to just make it easier for the baby to come through.2061

Right after delivery they will sew up that area, which is a lot easier repair than on torn tissue.2070

A breech birth means that the baby instead of being head down, the legs or some part of the body is closest to the cervix.2078

You cannot deliver baby normally with feet down.2090

It does not slide out the right way.2094

What they will try to do is try to manipulate the baby from outside of the mother’s abdominal region.2096

They will try to get the baby to flip over so that it is not a breech birth any longer.2103

But if they cannot, if they cannot get the baby flip over they will do caesarian section.2109

The other things can happen that I did not list here is sometimes the baby will get tangled in his or her umbilical cord 2116

and the problem with that is if the baby gets tangled in the cord and is pressing on with their body they are cutting off gas and nutrients to their bone ironically.2124

That means you are going to do an emergency delivery typically C section to get the baby out before it suffocates.2133

A C section is where they simply administer anesthesia then they cut into the abdominal area of the female 2140

so that they can see the outer wall of the uterus and they cut into that and then they take the baby out.2150

You can see right here that is what they are doing.2158

It looks kind of a cover for the baby like they are just pulling it out its head but you can see that this nurses is assisting the doctor in getting the baby out.2161

A premature delivery is if prior to the end of the 3rd trimester if the baby comes out really early like labor pains in week 35 or 30 or even late 20’s.2171

The problem with that is if the baby is delivered at the end of the 2nd trimester or very early on in the 3rd trimester 2191

the risk of a baby dying is very high because when they come out 2½ or 3 months early a lot of organs are underdeveloped.2201

Their sizes are extremely small size relative to a week 40 term means they are going to be losing a lot heat.2210

A baby is very susceptible to infections.2218

A premature delivery does not mean that is definitely a problem but the earlier they come out the worse it is.2221

I have mentioned with the respiratory lesson that one of the problems with an early delivery 2228

is the lungs are underdeveloped and the baby has enough surfactant yet.2234

And that is that chemical that helps keep the alveoli expanded so they are not collapsing.2240

A lot of times they will administer surfactants to that baby to help the lungs function normally.2246

Conjoined twins means that early on what can happen with that blastula, 2253

with that initial ball of cells or hollow region sometimes it just splits apart.2259

That one fertilized egg which has become ball of cells splits, that is identical twins and call it monozygotic twins because they came from one zygote.2265

If that separation that cleavage does not completely finish, that is conjoined twins called siamese twins but the better term is conjoined twins.2276

They can be conjoined just with parts of the skin which is very easy to surgically separate them.2286

Oftentimes they are sharing organs.2294

They might share a liver.2296

I saw on the news recently that there was a set of conjoined twins that basically look like they have one body with two heads.2298

They have 2 different spinal cords that fuse at the bottom and I believe they said that they have 2 different hearts.2307

That kind of surgery since they are so connected intimately with their organs they are not going to surgically separate them successfully.2317

Some conjoined twins depending on what organs they are sharing and 2326

how conjoined they can separate them other times it is not possible without them death happening.2330

Besides conjoined twins I want to mention the other way that the twins occur dizygotic would be 2 different eggs 2336

have been ovulated 2 unique eggs in terms that genetics.2345

2 different sperm fertilize them.2348

The majority of twins are fraternal twins not identical.2350

The chances of fraternal twins being identical is like one in millions.2355

Just like any 2 siblings born separately like years apart they will have some things in common but they came from different sperm and eggs.2358

The chances of having identical twins is something like 1 in 89 and approximately.2369

The chance of having triplets is 1 and 89 squared which is interesting to think about.2378

That is 1 in 7000 something.2387

And then a quadruplets its 1 in 89 cubed.2391

That is lot less likely of course.2397

Embryological conditions and disorders.2399

Here is the first one I listed is gestational trophoblast neoplasia.2403

GTN what is this?2409

The trophoblast that surrounds that initial blastula of cells, the way the trophoblast functions 2411

in terms of it growing rapidly invading tissues of the mother, the endometrium.2419

You are not being detected by immune cells.2425

It mimics cancer cells if you think about it what is actually doing.2430

Sometimes it is rare but sometimes that trophoblastic region will act like cancer and start invading internal tissues.2436

In that case if they detect the early on in the mother's pregnancy they have to remove that tissue 2446

as fast as possible and they will administer chemotherapy.2452

The baby is not going to survive that but it is a weird thing that can happen with the trophoblast region.2455

A miscarriage or spontaneous abortion means through no active choice of the mother it just happened randomly.2461

A miscarriage can occur early on in pregnancy or later in pregnancy.2473

Spontaneous abortion, the mother did not want it to happen and it just happen.2477

And there are lots of reasons this can occur.2482

A lot of reasons the baby cannot successfully develop a full term in the mother.2484

Drug use or alcohol abuse can increase the chances of a miscarriage.2489

Induced abortion is the technical term for when a mother elects to actually get the baby taken out of her.2496

Ectopic pregnancy is not very common.2502

If the women of childbearing age is sexually active and there is even a chance that she could get pregnant.2509

The first sign of ectopic pregnancy is a release of sharp pain down in the lower regions of the abdomen.2519

Not exactly where you have the pain of appendicitis but not far from there and that is a sign of an ectopic pregnancy.2527

What this is you will have fertilization and that ball of cells that have lower blastula 2535

is supposed to roll down the fallopian tube into the uterus and plant it there.2545

If that ball of cells implants itself in the fallopian tube and starts growing eventually this can result in a lot of pain 2548

because the actual diameter inside the fallopian tubes is only a few millimeters.2557

Early on in pregnancy the stretching of the fallopian tube is extremely painful.2562

The baby is not going to make it but you know if that is not dealt with the bleeding resulting from that could kill the mother.2567

This requires an urge to surgery to remove that particular embryo.2576

In Vitro fertilization is what a couple will do if they are having trouble with the fertilization in Vivo.2581

In Vivo means in a living being.2588

Natural sexual intercourse and natural conception is in Vivo.2591

In Vitro if the couple is having trouble they will take sperm from the man 2597

and eggs from the female mix them together in a laboratory like in Peachtree dish.2603

They will get a few little embryos and implant them inside the mother's uterus.2609

They will implant a few hoping that just one will take, that one will successfully be implanted in the endometrial lining and develop the placenta etc..2615

But oftentimes multiple ones actually implant make it to full term.2624

That is why the chances of having twins or triplets or quadruple etc. is much higher with in Vitro fertilization.2631

Amniocentesis is one of the tests you can do to see if there is birth defects early on in the pregnancy.2640

If there are chromosomal problems and they recommend this for women who were in their 40’s 2646

or earlier on or if there is a history of birth defects in your family.2650

Here is a normal cariotype.2654

Here is what they do.2656

They take a needle go into the amniotic fluid through the uterus and withdraw some of the amniotic fluid that surrounding the baby.2657

In that fluid you are going to get skin cells from the baby that are sloughed off, so many of those.2666

In the fluid you withdraw they are skin cells, you extract the DNA.2671

Before it is back in the DNA you can stimulate those cells to undergo mitosis so you have a lot more DNA to work with.2679

When you take up the chromosomes from a cell and they are laid out in pairs, the pairs that go together there should be 23 pairs.2685

You can see there is number 1-22 and here is the 23rd pair so this will be a male cariotype because here is an x and y chromosome.2693

If instead of xy was xx then it is a female.2700

Looking at the chromosomes they can diagnose certain chromosome disorders from this particular amniocentesis test.2704

Speaking of this test you can detect certain birth defects.2712

Down syndrome would be if you look up pair 21, down syndrome is cause by trisomy 21 meaning 3 copies in this particular part here.2717

You are supposed to have 2 copies of the 21st pair but having an extra 1 either from the sperm or 2728

the egg that happens to non disjunction errors during meiosis that you learn during biology.2734

Down syndrome has forms of a mental disability.2740

There are certain looks on their face if they have down syndrome because chromosomes associates pair 2746

has something to do with formation of the skull bones.2755

Down syndrome does not have a cure but even with down syndrome can live normal lives.2759

Turner syndrome rather than being on the 21st pair that is actually affecting sex chromosomes.2768

All of these 1 through 22 you got autosomes meaning they are non sex chromosomes.2778

If you are male there is a female out there on planet Earth who could have an identical chromosome 22 coincidentally 2792

but she looks like a female and you look like a man.2801

Only these right here chromosome 22 directly pertain to sex male and female.2804

Turner syndrome is when you are born with an x chromosome and no y.2812

They are female but underdeveloped in terms of the ability of them to like actually have kids and their genitalia is underdeveloped.2816

They usually do not look like a typical woman when they go through puberty.2827

Spina bifida basically mean split spine in Latin.2833

Spinal bifida means there was a problem with the development of the spinal cord and not being encased correctly in spinal column within the back.2838

Spinal bifida can be very minor meaning the spine is enclosed inside the back correctly and protected 2845

and there is meninges around it but sometimes parts of the spinal column meaning the bones do not completely encase or unsheathe the spinal cord.2857

Those people are a little bit more risk for certain injuries to their spinal cord is not fully protected.2871

The worse end of it is a baby born with severe spinal bifida could mean that part of the spinal tissue the spinal cord is actually outside the body.2878

That should risk of infection and the baby typically does not live long with that.2890

PKU is one of those few birth defects that if treated correctly you will see no negative effects.2894

PKU stands for phenylketonuria which means you are born with a dysfunctional gene in terms of your ability to breakdown phenylalanine.2903

Phenylalanine is amino acid in the body.2914

If you have PKU in the body can build up and cause the brain issues or brain problems.2916

But if you know your baby has this make sure you do not feed the baby phenylalanine 2924

and you will not see any long-term effects of PKU which is pretty amazing.2931

You can look up a list of what kinds of foods have a significant amount of phenylalanine.2936

These are only 4 birth defects in thousands of disorders that can happen.2941

If you are healthy and you do not have birth defects be thankful.2946

Thank you for watching