Anatomy and Physiology of Embryological Fetal Development

Anatomy and Physiology of Embryological Fetal Development

hi welcome back to educator calm this is the lesson on Embree illogical and fetal development so an overview of development from conception up to adulthood would go like this it starts with fertilization that is the moment of conception when sperm fuses with egg you're going to get what's called a zygote that's the first cell of life then from that point on it's embryo logical development until it becomes a fetus the first step in getting from zygote to embryo is what's called cleavage and that's a term for when cells physically divide the cytoplasm zand and separate so cleavage happens after telophase if you took biology recently but cleavage happens over and over and over and over you form a ball of cells and that ball of cells that has a hallow Center is called a blastula and then it goes through what's called gastrulation gas elation is a folding in and then you get defined layers within that ball of cells you get outer layers of cells middle layers of cells and inner layers of cells and then there's this gastrula development until we call it an embryo and it's called an embryo until about week nine and then from that point on it's a fetus and it's a fetus in through the second trimester third trimester and then eventually birth happens and then you have postnatal development so this baby here this cute baby is going to develop you know into a toddler child adolescence adulthood and eventually reach maturity and you die fertilization overview so how does fertilization actually occur what are the details it's fusion of a secondary oocyte and a spermatozoon or spermatozoa secondary oocyte if you saw the female reproductive system lesson that comes from what's called a BOGO Neum that's kind of like the stem cell that makes eggs and the secondary oocyte is more technical term rather than just calling it an egg or an ovum this is actually not completely done with meiosis and I'm going to cover that a little bit in the future in this lesson but once the sperm metazoan makes contact with it it will finish meiosis and then become that full-fledged ovum and each of these should have 23 chromosomes that's the haploid number that's chromosomes without a pair that go with that those chromosomes so when you have sperm and egg coming together you have 23 going with 23 chromosomes and that's how you get the diploid number of 46 once again the volume ratio when you compare the O site and the spermatocyte or spermatozoon is about two thousand to one volume wise so the amazing thing is that when you when you take one sperm and if you were to stretch it out with its you know little sperm head and an flagellum it's close to about half the length of the diameter of an egg cell but the volume is crazy different 2,000 times the volume in an egg and that makes sense because besides you know the sperm had having the nucleus there's not much else going on there when you look inside of an ovum one of those egg cells you've got a lot of cytoplasm outside of the nucleus but contained within the plasma membrane all the major organelles that you're going to have in that ball of cells in that embryo come from mom including mitochondria ER Golgi etc and those are a lot of what are called epigenetic factors just things other than DNA that are inherited from the maternal side and fertilization typically occurs within a day after ovulation in the fallopian tube so if it happens within the day after ovulation the part of the fallopian tube that is going to happen here is that infundibulum if you remember the fallopian tubes have those fimbriae that's closer to the ovary rather than closer to the uterus you know if fertilization happens where the sperm reach the egg and in the second day after ovulation or even the third day yes then the egg will have gotten closer to the body of the uterus and yes a zygote is forms I goat is the term for the first cell of a new life and that zygote should have 46 chromosomes if all well and here's a older micrograph of the surface of an egg cell and a sperm beau-site activation so once sperm actually come into contact with the egg you're going to have some things happening that are very important in this sequence so it's a series of events that are triggered when the plasma membranes of sperm and a site come into contact with each other first thing that happens is a block to polyspermy here's what that means that's a fancy way of saying the egg hardens its exterior so that no other sperm can penetrate once that first one has gotten through when you look at a bunch of sperm trying to penetrate an egg you have this region on the very outside that actually won't be won't be broken down unless a lot of sperm are poking at it all of their acronym is later on in this lesson but all of those little enzyme sacs at the edges of the sperm heads we're way that outer area and then you get to what's called the zona pellucida and once a single sperm penetrates the zona pellucida there's an immediate chemical reaction that hardens the outside because you don't want multiple sperm exiting or sorry entering rather one egg you want the diploid number you want 46 chromosomes you don't want 92 you don't want you know four copies of every chromosome that's not going to be a viable human being so block to polyspermy makes us that only one sperm head has actually entered the egg cell next thing completion of meiosis two so remember a secondary oocyte is is not quite a full-fledged ovum it's actually arrested in meiosis 2 so meiosis 2 completes once that sperm has entered and then also activation of enzymes and that increases metabolism so in an egg cell you have a lot of mRNA or messenger RNA strands that are just kind of hanging out in the cytoplasm and kept inactive by certain proteins but once the Oh site is activated by that sperm entering you turn on the mRNA and then you start synthesizing a lot of important proteins that are part of making an embryo so those things are on hold until it needs to start and once you have that diploid number once those chromosomes have come together in that zygote time to get a metabolism going because there's gonna be a lot of cell divisions only the nucleus of the sperm is supposed to move into the center of the oocyte you've got that middle piece of a sperm you're gonna hear more about later in this lesson and the flagellum those things don't stick around and a lot of times they fall off right after the sperm has come in and actually the egg has the potential to destroy those things if for some reason paternal the dad's side mitochondria stay around in the egg and they're not destroyed that actually results in a severe disorder that has a lot of impact on your muscle tissue so healthy individuals do not have paternal mitochondria all of the mitochondria that men and women have should be from their mother and that's because those mitochondria were in the cytoplasm of the egg cell and the ones from the sperm they just got the sperm to that destination they don't stick around typically oh and this is actually a micrograph of a no site they've removed some of the outer nourishing cells that the trophoblast cells they can hear more about later so you can get a better view of it but that is a no site alright cleavage so cleavage means that it is this this pinching in let's go through kind of what happens on a day by day basis day zero meaning that's the day that fertilization happened you get the first cleavage division and then by the time days gone by hey you've got two cells and the amazing thing is when we go through all of this all the way up to blastula we get a ball of cells the size does not change that's the amazing thing early on is that you have this large ovum and then all these cell divisions happen maintained in that that space you don't get a drastic increase in volume not quite yet so even when we get to the point where there's you know 80 something cells it's taking up the same space as we had at day zero when there was a zygote so day one two cells two cells divide to make four cells eventually you get to the point day three approximately where they say it's an early more EULA and amore Allah is a just a dense ball of cells and then day four more cell divisions have happened then we have an advanced Morla a little bit more cells taking up that space and then flash forward to almost a week into this day six we finally have what's called a blastocyst or blastula is another name for it and that's what you're looking at right here this this little picture is a hollow ball of cells with a nourishing layer called the trophoblast number four here what you're looking at is an inner mass of cells so I'm going to highlight that in yellow inner cell mass that's what's going to become the embryo these cells right here and you'll see what's going to happen of those later on in this lesson number 3/2 you're looking at the trophoblast layer around the outside of this and that is a nourishing body for this very very young life and eventually this trophoblast won't be needed eventually because it will be connected to the mother's blood supply but not quite yet this this particular blast chiller blastocyst has not anchored itself into get into the endometrial lining of the uterus and eventually you'll get a placenta coming out of that and an umbilical cord and all that but that's not quite yet number one is called the blastocyst you'll see let me spell it out for you so number one blasto seal I know it's a funny spelling but that sounds pretty blasto seal that is the hollow section in here and we'll see that even when we get to the the folding in you'll still see this this hollow section but yeah now we have a blastula and it's just kind of rolling down the fallopian tubes and into the uterus into the cavity of the body of the uterus plantation so now this is blastocyst is going to implant itself in the endometrium of the uterus and this usually begins at around day 8 it could be day 9 but day 8 usually an enzyme is secreted by the trophoblast from that outer layer into the endometrial lining allowing the initial implantation so it can kind of penetrate those outer layers of the endometrium lacunae little little holes or little channels that help to supply nutrients to the developing trophoblasts from the blood supply of the endometrium and there are these finger-like villi they look like little finger like projections extending from the trophoblast into the endometrium and these continue to develop to start to kind of suck nutrients into this area I should rephrase that initially what happens is is just diffusion its diffusion of nutrients so it's not they're not really sucking you know into the trophoblast region but diffusion is a passive process and there's a lot of blood flow from the mother into the endometrium you're going to see in the next few slides this is very important the blood cells that develop in this very early early new life those blood cells if you look at the haemoglobin of the fetal blood cells actually they have a higher affinity for oxygen than the maternal blood cells meaning that the babies early red blood cells are even more of a magnet for oxygen than the mother's red blood cells and that's going to be a very important piece of the puzzle in terms of how this works all right so after this blastocyst has implanted itself further development happens within that inner mass of cells by day 12 the inner cells of the blastocyst have developed into three distinct germ layers germ here don't think of bacteria think of like the word germination like like in plants in terms of like a seed you know developing and coming to be in terms of it making new life so germ in that sense that it's like a germination new life so there's three distinct germ layers the ectoderm mesoderm endoderm ecto outer mezzo middle and endo inner and i'm giving you some examples here of what these cells become and in a fully developed baby or human being that we can you know recognize this is not all of the tissues you can look up everything that the actor turn ectoderm becomes and everything that the endoderm becomes but these are some major parts and the way that they know this is by studying gastrulation and gastro as in the development into the embryo and fetus if you tagged certain cells with certain chemicals and those chemicals remain in the tissues that develop later on you know that those tissues are descendants from from the particular cells that you tagged and they've done this in animals a lot over the years so ectoderm that that outer layer that you see here in blue becomes the epidermis the outer layers of skin neural tissue the brain nerves everything skeleton nice odor i know you don't see that in this particular drawing but when this this folding it happens from from the blastula you do get like another folding in from this green area it almost looks like little ears so that folding in and in this section here and here is what gives you the mesoderm Meisel durum forms slightly deeper levels of skin like the dermis the muscles come from the mesoderm and your heart and blood vessels come from the museum and finally the innermost part next to this this cavity the space here they call the the blastopore and actually actually the arc entraron is the term for this the blastopore is just the opening into the arc and drawn my apologies but the endoderm you get the digestive tract glands a lot of different glands and the urinary system the way that i remember that the endoderm gives you the digestive tract is if you think of like the inside of the body the most inner holes the most inner cavities inside your body the digestive system comes to mind you have this pathway going all through your body from mouth to anus and the most inner passageways that stuff's moving through it's easy to think yeah that's the digestive tract and it's funny this blastopore we know in humans and in a lot of different animals vertebrates especially animals with spines this blastopore is is the first hole that we see in this gastrulation and that becomes the anus and other animals like if you look at insects the blastopore becomes the mouth so of course later on in our development you're going to see the mouth hole develop but blastopore becomes the exit for the digestive tract so it's no surprise that that this greenish layer cells gives rise to the digestive tract so gastrulation the forming of a gastrula is that folding in and establishment of germ layers that become the major tissues of the body when we look at what happens to the trophoblast those those surrounding nourishing cells they become different extra embryonic membranes membranes outside of the embryo itself yolk sac is one of them and this is an interesting thing you know we're not birds or reptiles that are you know born inside of this this little egg where you would actually need a yolk sack to nourish you but the yolk sac evolutionary biologists assume that this yolk sac is from our ancestors mammals came from a class of reptiles and we are mammals so yolk sac it's not filled with yolk it just doesn't actually contain yolk like you would see in a chicken egg but it is this sac that helps give rise to our blood cells that eventually are going to receive nutrients sorry oxygen specifically from from the mother through that that connection that placenta we're going to get to in a bit so the yolk sac once the placenta is established in the umbilical cord comes to be the yolk sac is kind of off to the side of the umbilical cord itself the amnion you may have heard of amniotic fluid yes the amnion ends up being this fluid filled region that surrounds the embryo protecting it you're going to get cells from the embryo stuffed off into it eventually the baby swallows amniotic fluid but yeah this is a fluid-filled region that surrounds the embryo and there's the amniotic sac that contains the amniotic fluid and as the baby develops it expands by the time you're into the the second trimester the amniotic sac has expanded a great deal and eventually is pushing up against the inner edge of the uterus the endometrium the allantois when I first saw this as a student I thought it was Alan tois but it's a the allantois is this little area that eventually gives rise to the urinary bladder and parts of this have to do with the establishment of that connection for nourishment and gases to the mother the chorion you see this term chorionic villi associated with Cori on this leads to the entrance of blood vessels feeding the gastrula so before we have a full-fledged placenta you have what are called chorionic villi by the time you're into week three in the first month of development before women typically know that they're pregnant you have chorionic villi that are helping to to get blood vessels from the endometrial lining to feed the baby at a certain point the trophoblast is not enough the trophoblast initially nourishes that you know ball of cells but once it grows to the point where it's thousands and thousands of cells you need a lot more entrance of nourishment and gases from the mother and chorionic villi a lot to do with that there's a test you can do later on a pregnancy called chorionic villi sampling and this is the tissue that they can get a sample of to test for certain kinds of problems that could be happening with the fetus so the placenta the placenta initially blood supply to the embryo enters through chronic villi so initially we wouldn't call that a placenta but through the chorionic villi and those arise from remember the allantois the alan TOEIC arteries and veins help that blood connection happen but by week five if you were to go in it with a camera and kind of look around you would see a placenta and from that point on the placenta is there it it grows a little bit as time goes on to help the growing baby but a full-fledged placenta has some major layers I want to introduce you so the decidua bacillus this is a basal layer and decidua means a falling off like deciduous leaves deciduous trees if you're wondering what's what's falling off thing look here this is a little image from Grey's Anatomy so here's the endometrium if you're wondering what we're looking at this whole thing here is the placenta and here's the umbilical cord it is anchored to the endometrium of the uterus and and usually it's towards the top kind of near the fundus of the uterus towards the top of the body or superior portion of the body of the uterus if the placenta is down to low next to the cervix that could lead to some problems especially during labor I'll get to that in a bit but the the deciduous part here what why do they call it this the decidua you see here there's little like breaks in these blood vessels and blood is just kind of entering this space that's what this is referring to that that this layer here parts of the embryo are sorry of the maternal tissues that have blood flow there's kind of a wearing away to the point where maternal blood just pours into this cavity and that's why I've said hey there's a cavity and here all this space here you can see it here it's the inter Villas space you can barely see that term but this space around the chorionic villi which are coming from the embryo you have maternal blood just coming into here and that's brilliant because think of the chorionic villi is kind of like little blood vessel branches little blood vessel trees in a sense and as long as you have maternal blood adjacent to it diffusion will bring those those oxygen gases the nutrients into the blood flow of the baby and what also happens is the waste from the baby enters into this cavity and can go back into the mother so the carbon dioxide being generated in the baby's body and the waste products from metabolism go the reverse way the umbilical cord that's right here and of course it's cut off you don't see the full thing but the umbilical cord goes into the belly button region what does become the belly button after the umbilical cord little nub falls off when a baby's been born but the umbilical cord has arteries and veins arteries going into the baby veins going back to the mother so here is a placental body when birth happens the placenta comes out they call it the afterbirth because after the baby comes out and you know the baby hasn't bulgor attached to it what's the other end of the iboga cord the placenta so once the baby is born there's no need for the placenta anymore that comes out after the baby so week four embryo by the time gas relation has happened and these different areas of that folded in ball of cells become parts that you can actually notice you know this doesn't quite look human but you can see some parts that are going to be more obviously human several weeks later if we looked at embryos of rabbits cows dogs they would actually look very similar to human embryos at this point in time but let me show you some of these different parts so the forebrain which becomes the majority of the higher brain that's right here forebrain is in this region the eye I think you can probably notice the eye already at week four right there the heart should have used red for that but I'll use blue so the heart right in this region the Ferengi arches up I already use green Pipal Franju large is what the heck are those alright so here they are the pharynx is the throat the amazing thing is that even in a human embryo you would see these little little Holdings looking like they could become gills they don't because we're human but this is one of those as far as we know vestigial structures kind of leftover remnants from ancestors in the ocean from hundred millions years ago I mean even reptiles you can trace their ancestry back to vertebrates in the water that breathed with gills so Franz you arches you would see them for a little while and then they don't develop into gills because of course we have lungs and we do not breathe underwater arm buds and leg buds I'm going to highlight those in yellow arm bud leg bud that's the cool thing is you just see little little they look like little nubs popping out where the arms are going to be and where the legs are going to be and if you flash for a few weeks later you would see a longer bud and it almost looks like a little paddle for the hand with no fingers and 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 what happens is this region is stimulated to die this region is stimulated to die the cells are signaled hey you're done and that's called apoptosis that's basically programmed cell suicide or cell death if that does not happen completely you would be born with webbed hands or webbed feet so there are places in an embryo where cells need to stop developing to create spaces and then tail we actually do have a tail for awhile as an embryo here it is you can see that this of course is going to become the spinal column you can even see already little divisions between the sections of what's going to become vertebrae but the reason why the tail doesn't look like a tail later on is the amount of growth in this part of the embryo compared to other parts gradually lessons so that it doesn't become a long tail we we grow into that tail bone so ends up being not visible outside the the buttocks region all right a week eight embryo about two months into the process this is bigger of course that actually is in real life the size of a week eight embryo about that big this is typically before a woman is showing before you could obviously know that she is pregnant but yeah about that big just a few centimeters about an inch long this baby the reason why we have this image is because it could have been a spontaneous abortion the baby was lost and in this tissue was preserved probably through the process of plastination which is a way that you can preserve tissues in a deceased body or organ from a deceased person and you can see a very early umbilical cord and how it enters into the the body yeah you can see it's about eight or nine weeks 38 millimeters or 3.8 centimeters you know close to an inch inch-and-a-half week 12 fetus by the end of the first trimester the the first approximately three months the rudimentary parts of all major organ systems have formed the heart is beating the brain has brain function there is a liver you know there are lungs are all of these ready for the outside world know the earlier the baby is born of course prematurely the the less developed the organs are so I'm going to talk more about you know premature births in terms of the danger of that but you could see with an ultrasound here that this this is a human baby and yeah ultrasounds have gotten better and better over time they're not all black and white and grainy anymore there's some good three-dimensional images from ultrasounds so speaking of ultrasounds how does that work 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 so the reason why even though there's sound waves we can't hear them is the frequency of these sound waves is beyond human hearing tens of thousands of Hertz sex can be detected between 18 and 22 weeks it really depends but potential birth defects and other problems are also observed so ultrasounds are not just for telling the mom and dad hey it's a boy it's a girl seeing the baby how it's moving how the body parts look can tell the ultrasound technician or a doctor if there are some other problems so technicians look oops that's a typo technicians look for obvious genitalia markers to determine sex so at this point in time when you're around the twenty week mark or so you can look at the genital region and see whether or not there's the labia majora you can see whether or not there's an early penis with the the testicular region all right flash-forward a great deal week forty fetus that's full-term birth happens at week forty I was actually close to the 41 I was I came a little bit later than was expected but you know plenty of births happen at at week 38 week 39 but week 40 this is an older image of kind of how the baby is situated a normal presentation meaning normal orientation of the fetus prior to birth is that the head is facing down towards the cervix towards the the birth canal and 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 to the side and this is one of the reasons that especially later on in pregnancy a pregnant woman has to go to the bathroom a lot because the bladder is being pressed upon that the colon the intestines are being pressed upon and also the stretching of all this material can stretch out the sphincters that that keep those things where they're supposed to be so yeah by week forty pregnant women feeling a lot of extra mass there and probably going to the bathroom a lot more but yeah now we're gonna move on to how does Labor happen so prior to week forty some women experienced false labor so these are little bits of contractions in the uterine muscles that don't lead to real labor and real birth so you know sometimes it'll be like week 35 or week 36 a woman will feel you know stuff going on down there go to the hospital and it's a false alarm the baby's not ready to come out yet true labor is when biochemical and mechanical factors reach the point of no-return the unconscious portions of the female brain have signaled hey it's time this baby is ready and labor contractions are what tell you it's true labor and we're talking initially there there are three stages initially it's dilation and what's dilating is the cervix remember the cervix is that bottom part most inferior part of the uterus and when it starts dilating it starts gradually opening so that the baby can start to come through the birth canal and initially you're going to get you know contractions that lasts about a half a minute and they happen every ten to thirty minutes so that's the beginning of it that's when it's like hey it's time to go to the hospital now a company with dilation usually they say oh my water broke what they're talking about is the amniotic sac itself inside the uterus has has broken the SAC itself has a hole in it and amniotic fluid comes out that's a sign that the baby's coming now if the amniotic sac gets a hole in it prior to dilation the danger of that is if now there's a hole in the amniotic sac where the baby is but there's no labor that puts the baby at risk of infection because now that protective area is open but the baby is just hanging in there still they sometimes will actually force labor to happen they'll though administer certain drugs to make labor pains happen and to get the baby out as soon as possible but typically associated with dilation is that that water breaking next up is expulsion that's where there are significant contractions of the uterine muscles we're talking those labor pains lasting longer periods of time and happening every few minutes that means that the baby is going to be expelled out and this this can sometimes just be you know one or two hours I can last a lot longer in some women but then the end result of expulsion is delivery of the baby this is when the baby has actually exited the birth canal is actually born so here are some delivery problems or issues that can come up an episiotomy is if the baby coming through the birth canal is too much for for the birth canal opening for the vaginal opening to bear instead of risking a tearing of the perineum meaning the the tissue next to the the vagina opening instead of you know having that tearing the doctor will make incisions in that region to just make it easier for the baby to come through and right after delivery they'll sew up that area which is a lot easier to repair than just you know torn tissue a breech birth means that the baby instead of it being you know head down the legs or some of the part of the body is closest to the cervix you can't deliver a baby normally with with feet down it just it doesn't slide out the right way and what they will try to do is try to manipulate the baby from outside of the mother's abdominal region they will try to get the baby to flip over so that it isn't a breech birth any longer but if they can't if they cannot get the baby to flip over they'll do a c-section or caesarean section the other things that can happen that I didn't list here is sometimes the baby will get tangled and her umbilical cord and the problem with that is if the baby gets tangled middle cord end and is pressing on it with their body they're cutting off gas and nutrients to to their own body ironically and that means you've got to do an emergency delivery typically a c-section to get the baby out before it suffocates but a c-section is where they simply they administer anesthesia of course but they they cut into the abdominal area of the female so that they can see the outer wall of the uterus and they cut into that and then they take the baby out and you can see right here that's what they're doing it looks kind of uncomfortable for the baby like they're they're just pulling it out its head but you can see that this nurse is assisting the doctor in getting that baby out premature delivery premature delivery is if you know prior to that the end of the third trimester if the baby comes out really early like labor pains you know in in in week let's just say you know 35 or week 30 or even late 20s the problem with that is if if a baby is delivered at the end of the second trimester or very early on in the third trimester the risk of the baby dying is very high because when they come out you know two and a half three months early a lot of their organs are underdeveloped and their size they're they're extremely small size relative to a week forty term is means they're going to be losing a lot of heat and the baby is very susceptible to infection and such so premature delivery doesn't mean there's definitely a problem but the earlier they come out the worse it is and I mentioned with the respiratory lesson that one of the problems one of the many problems with an early delivery is the lungs are underdeveloped and the baby hasn't produced enough a surfactant yet and that's that chemical that helps keep the alveoli expanded so they're not collapsing so a lot of times they will administer surfactant to that baby to help the lungs function normally conjoined twins means that really on what can happen with that blastula with that initial you know ball of cells with a hala region is sometimes it just splits apart that that one you know fertilized egg which has become ball cells splits that's identical twins they call it monozygotic twins because they came from ones I go from ones from one egg but if that that separation that cleavage doesn't completely finish that's conjoined twins used to be called Siamese twins but the better term is conjoined twins they can be conjoined just you know with parts of the skin which would be very easy to surgically separate them but oftentimes they're sharing organs they might share a liver i actually saw in the news recently that there was a set of conjoined twins that basically looked like they have one body with two heads they of course have two different spinal cords that fuse at the bottom and I believe they said that they had two different hearts that kind of surgery since they are so connected intimately with their organs they're not gonna be able to surgically separate them successfully so some conjoined twins depending on what organs they're sharing and how can join they are they can separate them other times it's not possible without death happening besides conjoined twins I just want to mention the other way that that twins occur dizygotic would be two different eggs have been ovulated two unique eggs in terms of their genetics two different sperm fertilize them the majority of twins are definitely fraternal twins not identical and the chances of fraternal twins being identical is like one in millions just like how any two siblings born separately you know maybe years apart they'll have some things in common but they're they came from different sperm different eggs the chances of having identical twins is something like one in eighty nine approximately the chance of having triplets is one an eighty nine squared which is interesting to think about that's one in 7900 in something and then quadruplets 1 and 89 cubed that's a lot less likely of course embryological conditions and disorders so here's the first one I listed is one you probably have never heard gestational trophoblastic neoplasia what Shoji Tian what is this well the trophoblast that surrounds that initial blast EULA of cells the way the trophoblast functions in terms of it growing rapidly invading tissues of the mother you know the endometrium and you know not being detected by immune cells it kind of mimics cancer cells if you think about it what it's actually doing so sometimes it's rare but sometimes that trophoblastic region will act like cancer and start invading maternal tissues in that case if they detect that early on in the mother's pregnancy they have to remove that tissue as fast as possible and they will administer chemotherapy so of course the baby's not going to survive that but really weird thing that can happen with that trophoblast region a miscarriage or spontaneous abortion means through no active you know choice of the mother it's it just happened randomly a miscarriage can occur early on in pregnancy even later in pregnancy so spontaneous abortion the mother didn't want it to happen it just happened and there's lots of reasons this can occur lots of reasons the baby didn't successfully develop to full term in the mother of course drug use or alcohol abuse can increase the chances of a miscarriage induced abortion is the technical term for when a mother elects to actually get the baby taken out of her and terminated ectopic pregnancy is not very common but if if a woman of childbearing age is sexually active and there's even a chance that she could get pregnant the first sign of next topic pregnancy is a really severe sharp pain down in the lower regions of the abdomen not exactly where you would have the pain of an appendicitis but but not far from there and that's a sign of an ectopic pregnancy what this is is you'll have fertilization and that that ball of cells that they you know that more yellow or blastula you know it's supposed to roll down from the fallopian tube into the uterus and implant itself there well if that ball of cells implants itself in the fallopian tube and starts growing eventually that's going to result in a lot of pain because the actual diameter inside the fallopian tubes is only a few millimeters so early on in pregnancy the stretching that fallopian tube is extremely painful and the baby is not going to make it but you know if that's not dealt with the bleeding resulting from that could kill the mother so this this requires an emergency surgery to remove that particular embryo in vitro fertilization is is what a couple will do if they're having trouble with the fertilization in vivo in vivo means you know in a living being so natural sexual intercourse and natural conception is in vivo but in vitro if a couple's having trouble they will take sperm from the man eggs from the female mix those together in a laboratory like in a petri dish then they'll get a few little embryos and implant them inside the mother's uterus they will implant a few hoping that just one will take that one will successfully be implanted in the endometrial lining and develop a placenta etc but oftentimes multiple ones actually implant and make it to full term that's why the chances of having twins or triplets or quadruplets etc is much higher with in vitro fertilization amniocentesis is one of the tests you can do to see if there's birth defects early on in the pregnancy if there's chromosomal problems and they recommend this for women who are in their 40s or later on or if there's a history of birth defects in your family so here's a normal karyotype here's what they do they take a needle go into the amniotic fluid through the uterus and withdraw some of that amniotic fluid that's surrounding the baby in that fluid you're going to get skin cells from the baby that have slept off so many of those so in in the fluid you withdraw there's bound to be some of those skin cells you extract the DNA you can actually before extracting the DNA you can stimulate those cells to undergo mitosis so you have a lot more DNA to work with and when you take out the chromosomes from a cell and they're laid out in pairs the pairs that go together there should be 23 pairs and you can see there's all the numbers 1 through 22 and here's the 23rd pair so this would be a male karyotype because here's an X chromosome here's a Y chromosome if instead of XY it was xx well then we know it's a female so looking at the chromosomes they can diagnose certain chromosomal disorders from this particular amniocentesis test speaking of this test you can detect certain birth defects Down syndrome would be if you look at pair 21 Down syndrome is caused by trisomy 21 meaning 3 copies in this particular part here you're supposed to have two copies of the 21st pair two pair but having an extra one either from the sperm or the egg and that happens through nondisjunction errors during meiosis that you may have learned about in biology Down syndrome a you know has forms of mental disability there's a certain look on their face if they have Down syndrome probably because chromosomes associate with this pair have something to do with formation of the skull bones but yes Down syndrome doesn't have a cure but individuals Down syndrome can live normal lives Turner syndrome Turner syndrome rather than it being on the 21st pair that's actually affecting sex chromosomes so all of these 1 through 22 I'll make a box around them 1 through 22 you've got autosomes meaning they're non sex chromosomes so if you're a male there's a female out there on planet earth who could have an identical you know chromosome 22 you coincidentally but she looks like a female you look like a man so only these right here chromosome 23 directly pertain to sex being male or female Turner syndrome is when you're born with an X chromosome and and know why so they are female but but underdeveloped in terms of the ability of them to like actually have kids and their genitalia is underdeveloped and they usually don't look like a typical woman when they go through puberty spina bifida basically means split spine in Latin spina bifida means there was a problem with the development of the spinal cord and it being completely encased correctly in the spinal column within the back so spina bifida can be very minor meaning the spine is is enclosed inside the back correctly and protected and there's meninges around it but sometimes parts of the spinal column meaning the bones don't completely encase or and sheath the spinal cord so those people are a little bit more at risk for certain injuries to their to their spinal cord because and not completely protected the worst end of it is a baby born with severe spina bifida could mean that part of the spinal tissue the spinal cord is actually outside the body and that's huge risk of infection and the baby typically doesn't live long with that PKU is one of those few birth defects that if treated correctly you will see no negative effects PKU stands for phenylketonuria which means you were born with the gene a dysfunctional gene in terms of your ability to break down phenylalanine so phenylalanine is amino acid in the and if you have PKU phenylalanine in the body can build up and cause brain issues brain problems but if you know your baby has this make sure you don't feed the baby phenylalanine and then you will not see any long-term effects of PKU which is pretty amazing and you can look up a list of what kinds of foods have a significant amount of phenylalanine but anyways these are only for birth defects in thousands of disorders that can happen so if you're healthy and you don't have birth defects be thankful so thank you for watching educator com

4 thoughts on “Anatomy and Physiology of Embryological Fetal Development”

  1. great lesson, i absolutely loved it. Wished you would've used more visual, kind of how khan academy does it! Overall i totally loved it <3

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