so the fetal development goes from nine weeks until birth and the placenta is functioning by the end of the third month that means that that corpus luteum is going to shrivel up and it is going to become the corpus albicans which is scar tissue that always happens corpus hemorrhagicum corpus luteum corpus albicans the only difference is that the amount of time it spends is the corpus luteum is going to vary according to whether you're pregnant or not if you're not pregnant it's going to have a much shorter window of time during which it's the corpus luteum if you are pregnant then it's going to stay the corpus luteum for a couple of months until the placenta is producing hormones and stops sending the signal that human chorionic anatotropin all right so here we have that process we have fertilization in the uterine tube and then we have cleavage occurring and we make a morula and it's moving through here through both ciliary action as well as peristalsis and then it gets in here and we have ourselves a blastocyst and so it is a hollow it's going from a solid ball of cells to a bigger ball of cells because we've cracked open that zone of pellucidus now this guy can get bigger and it's going to have cells all around the outside called the trophoblast it's going to have a fluid-filled interior called the inner cell mass and it's going to or the embryoblast and then the cells around the outside are called the trophoblast and then the fluid filled area inside is the blastocell and then it's going to implant about six days after fertilization and the trophoblast is going to release the enzymes that are going to digest its way and it's going to start trying to hook up with the blood supply that's in here actually it's almost like a little parasite right there because as it's digesting its way into the stratum functionalis it's using the nutrients from that digested tissue for growth okay so it's feeding off of it essentially as it digests its way in all right so do do do do we talked about capacitation and it it takes about six hours four to six hours for capacitation to occur so it's it it's even more of a schedule that the sperm have to be under in order to get to the egg in time so the egg is 24 hours the sperm 48 but they have to spend four to six hours at 48 undergoing capacitation before and then they have to swim and they are so teensy tiny that's a real long distance to swim through the uterus and then in through the uterine tubes um prostaglandins remember that's a component the semen that comes from the seminal vesicles they cause uterine contractions and that helps to push the sperm through the uterus as well all right fusion sperm the secondary oocyte cingamine thigami and fertilization are often used interchangeably those words polyspermy is prevented by chemical changes and here we have the way that it pushes its way in and once it does this is going to complete meiosis ii here it's in anaphase here's that first polar body and now we're undergoing the first and second the fast and slow um blocks to polyspermy um the fast block remember one to three seconds after contact uh the oocyte membrane depolarizes and then that also is going to trigger the intracellular release of calcium that causes and it's it causes exocytosis of molecules that harden the zone zona pellucida and they also destroy those zp3 receptors so even you know it's hard and now the guys can't bind to it and have that acrosomal reaction that releases all those enzymes that help um that help it okay and we talked about twins before and we talked about this and this is making the morula and you can see on the outside we still have that zone of pellucida so as the cell divisions occur the cells get successively smaller all right we talked about that okay all right so uh seven eight days after fertilization is implantation and remember there's a window of time during which it has to happen where everything has to be right and the trophoblast is going to get two layers this in sensadio trophoblast and the cytotrophoblast cytotrophoblast is going to be the area right around the embryo and the it's insideiotrophoblast is what's going to be secreting the enzymes that are going to digest through and so over here would be you're going to have the sensatio over here where it's going to digest its way through so um this incideo then these cells actually fuse together and make this yellowish area so this whole yellowish thing is this insideiotrophoblast and it has digestive enzymes and it's it's pushing its way through and it it creates these lacunae remember lacuna means cradle and these generally are filled with blood and that's providing them with oxygen and nutrients as well and it's going to start sending out little branches that are going to become the chorion so here this blue is the inner cell the inner cell mass and inside of it we're it's going to start to differentiate and inside we're going to have the amniotic cavity okay and this is starting to differentiate this is the embryo and it's starting to create specific layers and then on the outside of the embryonic part you're going to have the the cyto trophoblast okay so the sensatio is what's digesting through it's this yellow and it all fuses together to become this multi-nucleated kind of weird mess and this part here is the the um cytotrophoblast that's going to help uh become part of this embryonic structure here and this is actually starting to develop into layers that are going to become different parts of the um embryo and this area here now is called the yolk sac okay um so the uterus the endometrium is now it's also called the after implantation it's called the decidua and so there's three regions deciduous basalis deciduous capsularis and decidual parietalis the basalis is between the chorion and the stratum basalis of the uterus and that's the maternal part of the placenta the capsularis covers the embryo and the parietalis is the rest of it so the basalis would be over in here and that's going to become the female's contribution to the endome to the placenta the capsularis is going to be around the rest of this embryo and then the rest of the uterus the area up here there the endometrium excuse me the area down there the area up here the part that's not contacting this uh embryo is the parietalis all right eggtopic pregnancy is when it occurs outside of uterine tube placenta previa is when the placenta is planted near or covering the us of the cervix and that is often a very dangerous condition in which the mother can can bleed out as well as the baby can die and generally you just see bright red blood coming out of the vaginal cavity um near i think it's the seventh month is it in the third trimester yeah and so they'll get put you on bed rest and and deliver it by c-section now um so normulation that's the beginning you create an organization tube um and development of nervous system happens real early on the heart begins to form and pump blood and then the limb buds the allen toes forms and the allen toes um is contained within the umbilical cord you can't see in this picture we have limb here we go so the blue here is the amnion the amniotic cavity and remember when somebody's water breaks that's what it is the fluid that's in there and then here we have the alantois this little green guy and this is going to be become part of the umbilical cord all right so the allen toast and the yolk sac are parts of the this yellow here and the green are parts of going to be part of the umbilical cord these little guys that are sticking out here like little decorations little snowflakes on a christmas ball or something these guys are the chorion the chorionic villi the dark pink structure is the chorion these are the chorionic villi and the chorionic villi are what they sample when they do hence the name chorionic villi sampling um when they're trying to do an early test to see if the baby is normal okay so first they look like little dragons with little limb buds and a tail and a little dragon head and the same it's difficult at this point to tell the difference between a human embryo and other uh embryos um the same structures here that are going to become the thymus and parathyroid and so forth are going to become guilts in fish and amphibians so by the end of eight weeks the embryo is only 38 millimeters an inch and a half long but now it's starting to look less like a little dragon and more like a human and then we start to have bone replacing cartilage remember we start with that cartilage model well now the bone is starting to replace it and you start seeing the epidermal refinements you also see in third and fourth months you start to see the individual fingers and individual toes being carved out and remember that's apoptosis that's doing that you can also see the genitals the genitals have differentiated from male and female and you can hear a heartbeat and this is what a baby that age looks like alpha feta protein is a blood test and the higher the levels are the more likely there is that something either you're having multiple babies or something's wrong with your baby it could be like a neural tube defect lenugo is the hair that covers babies the fur and vernex casiosa is the cheesy like substance that covers the babies okay so their circulation remember is going to bypass the lungs and it doesn't mean the lungs don't get nutrients that's coming from the bronchial blood vessels not the pulmonary pulmonary is there to pick up oxygen well you don't have oxygen in there so you're not going to be picking up oxygen you're going to bypass that system and you do that through the the uh foramino valley that oval hole in between the right and left sides of the atrium right and left atrium i should say and we also have um the uh ductus arteriosus that is a connection between the pulmonary trunk and the aorta that allows the shunting of blood so um the umbilical arteries branch off the iliac arteries and you can see them right in here in some umbilical arteries okay and they are and remember arteries take blood away from the heart and so they're taking deoxygenated blood to the placenta the umbilical veins are bringing oxygenated blood in so the veins in this case will be red they're going towards the heart the blood vessels going away from the heart our arteries and they're going to be blue okay um and the chorionic villi remember are going to project into the maternal tissue as it develops and by the 10th week the placenta is fully formed secretes estrogen and progesterone you don't have mixture of fetal blood and maternal blood however certain things can cross igg can cross so if a woman is exposed to some disease-causing organism she will transmit the antibodies to her baby while it's in utero and then if she nurses it will also be transmitted through her her breast milk ultrasound is good to see a lot of things it's ultrasound think about ultrasound is what you can see so if there is some type of genetic abnormality like cystic fibrosis you can't see that by looking at the baby all you can see is get an idea how big the baby is you can measure it they have tools where they can measure it you can so that you can get a closer idea of how old it is if you're unsure when you got pregnant um you can uh using ultrasound you can see if you have multiple births you can tell if it's a boy or a girl you can see how it's positioned you can see i mean there's a lot of stuff you can tell from it there's a lot of things you can't tell and so if you're looking for specific abnormalities amniocentesis or chorionic villi sampling are going to be the best bet