Embryology | Development of Fetal Circulation

all right ninja nerds in this video today we are going to be talking about the fetal circulation before we get started please hit that like button comment down in the comment section and please subscribe also down in the description box we'll link to our facebook instagram patreon account go check that out all right engineers let's get into it all right ninjas when we talk about fetal circulation we have to approach this in particularly two ways i want to talk about the fetal circulation while the baby is actually still in utero so before birth go over

the flow of blood throughout that fetal circulation pathway then after we do that we're going to go into the next step which is talking about fetal circulation after birth so once they cut the umbilical cord and then finally what we'll do is we'll end off talking about what some of the fetal structures that are involved in the fetal circulation become as an adult remnant if you will all right first things first when we talk about fetal circulation before birth i have to kind of start everything off with a little pathway first so we talk about

the baby right the baby is actually sitting in amniotic fluid if you will right so it's not actually breathing in air all the oxygen that the baby needs is coming from the placenta that's the source of oxygen when the baby is in utero right we said that they're not taking in any oxygen so when we look at the oxygen concentration inside of we zoomed in on one of these alveoli and zoomed in on it the oxygen concentration would be pretty much zero what we're just gonna put for the sake of it here we're gonna put

really really really low but it'll pretty much be zero now normally if you guys remember from your pulmonary physiology whenever you have low amounts of oxygen in the alveoli remember you have those pulmonary capillaries and those pulmonary capillaries are taking blood and moving it to the actual alveoli where what will happen in this process you'll move co2 from the blood into the alveoli and oxygen from the alveoli into the blood and that's that gas exchange process that occurs in adults whenever there's crazy low oxygen in the alveoli you know what it does to this pulmonary

vasculature it constricts the pulmonary arteries that are coming to that area so what does it do again whenever there's really low amounts of oxygen this induces what's called vaso constriction and this is particularly in the pulmonary circulation now whenever you vasoconstrict the blood vessels the whole design is that you're going to shunt this blood from going into this alveoli potentially to another alveoli so let's say that we drew another alveoli here and theoretically the goal is to shunt this to another alveoli where there's going to be lots of oxygen that's the whole reason you're constricting

this one to shunt it to another area but guess what all the alveoli have crazy low oxygen so not only will you vasoconstrict here you're going to vasoconstrict multiple alveoli so there's going to be what a significant intense degree of vasoconstriction and that significant vasoconstriction and the pulmonary circulation which vessels here the pulmonary arteries it is going to increase the pulmonary artery pressure when you increase the pulmonary artery pressure that translates to which side of the heart which side of the heart pumps blood into the pulmonary arteries the right side of the heart so now

not only will the pulmonary artery pressure be high but now the baby's right ventricle and right atrial pressures are going to be high because it has to pump a lot more pressure has to generate a lot more pressure to pump blood into this high pressure circuit so because of that high pulmonary artery pressure due to intense vasoconstriction due to hypoxia in this case because the baby is in amniotic fluid does not getting oxygen through breathing that is going to increase the right side pressure so all the pressures on the right side of the heart are

going to be higher than the pressures on the left side of the heart and the baby so that's what i want you to remember next the last thing here is that right side pressure of the heart is greater than the left side pressures of the heart i can't preface how important that is to really understanding this fetal circulation process there's a particular name for this that we call it that we actually call it in um and pulmonary kind of like your physiology classes this right here this kind of process here is called hypoxemic hypoxic or

hypoxemic we're going to just say hypoxic vasoconstriction okay hypoxic vasoconstriction and this is what is happening within that pulmonary circulation when the baby is in utero during the birth process well actually before it's actually born all right so now we have this concept it really should make sense now what is going to happen in this fetal circulation before birth so let's kind of annotate what we have here in our diagram this right here this portion here is going to be the placenta so this is basically you know the placenta has many different functions it can

release hormones but one of the big things related to the fetal circulation is it's responsible for picking up co2 so it removes waste and removes co2 and then helps to provide oxygen into the blood okay so let's actually kind of follow this flow here all right the first thing that you're going to start with is these blue kind of veins here that we're going to start with these blue veins that is running through this next structure this here is the placenta okay this part here is the placenta but then from here you're gonna have a

cord you know what this cord is called this whole cord here this is called the umbilical cord and within the umbilical cord runs a couple different things the first one that we're going to focus on is this one here that i'm kind of putting like little asterisks with this is your umbilical vein so blood is going to be running from the placenta via the umbilical vein do you guys remember which technically if we really want to be specific which umbilical vein actually persists at the actual development of the vascular system was it the right or

the left one it was weird because it was the left umbilical vein but we're just going to call this the umbilical vein because there's only one of them and it's the left one that persists do you guys remember though from the development of the vascular system this vein here which is called your umbilical vein it empties its blood right we said that it formed two connections one is it gave off a connection here to what's called the sinusoids within the liver that was one of the connections but the other connection that was even more interesting

was this connection starting here to this connection ending here this connection here is the big connection between the umbilical vein and this structure that we're going to kind of annotate here which is going to be the inferior vena cava okay so we called this technically remember from the development of the vascular system we said it was the hepatic portion of the inferior vena cava the umbilical vein is taking blood moving it towards what the inferior vena cava and it's connected to the inferior vena cava via this dark structure here what is this dark structure here

called this is called the ductus venosus and what the ductus venosus is is it's a structure that shunts blood from the umbilical vein into what into the inferior vena cava now here's the next question you should be asking okay we know blood is coming from the placenta we said that the placentas are designed to be able to remove co2 from the blood okay and then provide oxygen what kind of blood is this umbilical vein carrying here's where it's kind of like it's weird you wouldn't think of it usually you associated oh arteries are red veins

or blues that means arteries or oxygen and veins are always deoxygenated this is not one of those cases the umbilical vein is actually containing oxygenated blood so there's higher amounts of oxygen umbilical veins than there will be in the umbilical arteries generally it's somewhere around 85 percent saturation of oxygen that umbilical vein is it takes blood oxygen your blood empties it into the inferior vena cava via the ductus venosus then from the inferior vena cava blood is going to move upwards when it comes up from the inferior vena cava the hepatic portion of it let's

test your knowledge what did the hepatic portion of the inferior vena cava come from which are the veins during the development the vitalin vein which one the right vitiline just wanted to see if you guys remember i know you guys did because you're awesome engineers but blood's going to empty in via that inferior vena cava into the right atrium so now there's here's going to be blood here let's actually put right atrium right over here so this is our right so the inferior vena cava takes the blood there and empties it into the right atrium

now once the blood comes into the right atrium via the inferior vena cava there's also some other blood supply that's coming from the baby what's this guy this is called the superior vena cava and the superior vena cava is bringing blood from the head and neck area right and we talked about the superior vena cava came from the right common cardinal vein remember that all right blood is coming from the superior vena cava and inferior vena cava and coming into the right atrium now remember what i told you when we compare pressures between right side

and left side here's going to be our left atrium do you remember in the development of the heart there was a hole between the atria called the what foramen ovale there was a hole between the right atrium and the left atrium if you really remember though it's a little bit odd if you kind of imagine here when we looked at that actual that light that separation between the atria there was actually what structures here that made it up remember this was called the septum intermedium and then this line coming down here was called the septum

primum and then there was a hole that developed up here called the ostium secundum and then there was a line that came down here that was called the septum secundum right and the space here where blood can flow this would be right atrium this would be left atrium this space where blood could flow is called the foramen valve now if the pressure in the right atrium is higher than the pressure in the left atrium because of all this process we talked about hypoxia vasoconstriction where would the blood more likely go think about this for a

second down here we're going to have right ventricle and here we'll have left ventricle right what do we say the pressure in the right side is if you had to compare pressure wise right ventricle the pressure is going to be pretty high because we said right side pressures are high left atrial pressure is going to be low so the blood would not want to go which way it's not really going to want to go this way because the pressure is higher that way blood likes to go from areas of high pressure to low pressure so

it's not going to want to go to the right ventricle that much it's going to want to go to the left atrium the where there's less pressure so blood will technically flow from this area in via the foramen ovale which is between the right atrium and goes into the left atrium now blood is here in the left atrium where does that blood glow go then from the left atrium blood can be pumped down here into the left ventricle from the left ventricle the blood can then be pumped where up via the aorta through the aortic

semilunar valve when it goes up through the aorta it then can do what continue on its direction to go through the ascending aorta through the aortic arch and then down via the descending aorta and we'll talk about where it can go from here in a second now when i said that all the blood goes to the left atrium from the right atrium through the foraminal bowel val that's not always like true if i were to say like if i made an imaginary percentage i'm completely making this up but if i said how much of the

blood is going from right atrium to the left atrium let's just say i'm saying 70 percent that means that there's still maybe 30 percent of that blood that moves down from the right atrium into the right ventricle because not all of it is going to go in that direction so there's still a little bit of blood that makes it down here into that right ventricle okay that's fine so let's hear let's denote this as right ventricle all right beautiful so i have my right ventricle if blood comes down here into that right ventricle the next

place it's going to go is up via the pulmonary trunk through the pulmonary semilunar valve as it goes up through the pulmonary trunk it can split and get ready to go into these arteries i'm going to put a little structure here there's a big big structure here that's going to be connecting the pulmonary arteries though to this structure here called the aorta as blood is flowing through the pulmonary trunk it has an option here it can go through the pulmonary trunk and into the pulmonary arteries right or it can go through this little hole here

between the pulmonary arteries and the aorta let's go back to pressures if we think about this right side pressure pulmonary artery pressures are going to be high right the aorta is taking blood from the left ventricle so technically the aorta is actually a left-sided pressure when you think about it with respect to the heart and circulation so pressure here in the aorta is going to be lower than the pressure within the pulmonary circulation we're just going to put circulation put circ right there for a second so when you're talking about pressure the pressure in the

order is less than the pressure in the pulmonary circulation because of this process we talked about the hypoxic vasoconstriction so where is the blood going to want to flow is it going to flow into the high pressure pulmonary circuits or into the low pressure aortic circuit it's not going to want to go to the pulmonary circuit it's going to want to go to the aortic circulation and then continue down via the descending aorta and then down here to the next structures we'll talk about what in the heck is that little tube that's connecting the pulmonary

trunk to the aorta that structure there is called the ductus arteriosus it's called the ductus arteriosus and that is a little bridging connection between the pulmonary trunk and the aorta now i want you to think about this for a second we said that the baby is in when it's in utero it's kind of sitting in amniotic fluid there's no reason for very much blood to go to the lungs because there's not going to be any gas exchange occurring there so why send blood there what did we do with the process of using that foramen ovale

and that ductus arteriosus do did any blood really get into this pulmonary circulation from this process because it was supposed to go technically right we said it would go into right atrium it should go to right ventricle but we had blood shunted into the left atrium that took some of the blood going into the pulmonary circuit then was supposed to go right atrium to right ventricle pulmonary trunk but then we have the ductus arteriosus that shunts it away from the pulmonary circulation so now do you see any lines here going to the pulmonary arteries no

that is why that process happens it takes and prevents blood from going to the lungs because we don't need it to go there all right now what happens that that blood is going to continue down let's go back to where pretty much most of the blood went into the left side circulation into the aorta it's going to come down the descending aorta and then bifurcate this part where it bifurcates this is called your common iliac arteries right your cias okay then from here it splits let's say i put like a imaginary line here this would

be your external iliac arteries this would be your external iliac artery these ones here and then you got these ones here these are called your internal iliac arteries blood is going to flow via the common iliacs and then into the internal iliacs and then from the internal iliac there's a portion of the internal iliac which we kind of like show this stripy color here that's her umbilical arteries so then from your internal iliac arteries it's going to flow into these structures which are going to take blood lead the umbilical cord back to the placenta and

again when it does it takes it back through these structures what are these vessels here called these are called your umbilical arteries and how many do you have two that is important the next thing i need you to understand about the umbilical arteries is if we had umbilical veins taking oxygenated blood from the placenta to the baby what do you think the umbilical arteries are taking blood from the baby to the placenta what kind of oxygen do you think it is in deoxygenated blood so i want you to remember this as low oxygen maybe like

50 percent oxygen saturation when you think about it then from there what do you think is going to happen well blood will move via the umbilical arteries and they'll go to the placenta you know there's what's called a chorionic uh arteries and the chorionic arteries will go to what's called the chorionic villi we talked about that in the development of the placenta video it'll undergo the gas exchange process dropping off co2 which one will drop off co2 umbilical arteries they'll pick up oxygen and then come back via the umbilical veins and we just start the

whole circulation all over again this is what's happening during the fetal circulation before birth now let's cut the cord see what happens after birth so after birth you cut that cord right now the placenta is no longer the organ that's acting like the lungs if you will for the fetus now the fetus has to breathe on its own you cut the cord now there's really no oxygen supply that is going to be coming via those umbilical veins so we need to understand now that once you cut the cord the baby is actually giving birth it's

no longer an amniotic fluid it has that first cry boom air starts coming in air starts flushing into the lungs then because the baby is now exposed to air and if those muscles are working well and if their surfactant is perfectly coated then what happens oxygen should start flooding into these alveoli if the oxygen starts coming into the alveoli what happened in comparison to what we had before birth it was really low it's going to go up the oxygen concentration will go up if the oxygen concentration goes up what happens to those pulmonary vessels that

are going to the lungs if there's good oxygen we want blood to go there we don't want to clamp down and send it somewhere else so because of that is there going to be a lot of vasoconstriction here no so there shouldn't be very much vasoconstriction at all there should be very very little vaso constriction going to the these pulmonary arteries if there's less vasoconstriction what happens to the pressure then within the pulmonary circulation it starts dropping so now the pressure and the pulmonary circulation so the pulmonary pressure starts dropping so that pulmonary artery pressure

starts dropping if the pulmonary pressure the pulmonary artery pressure starts dropping what happens to that right side pressure on the heart what happens to that right side heart pressures the right heart pressures starts dropping and as the right heart pressure starts to drop if you compare that with what happens to the left sided pressures what's going to happen then then the actual right side pressures we'll put right side pressures will start becoming less than the left pressures the left-sided heart pressures so now we're going to shift the direction of the blood flow right so is

there going to be any hypoxic vasoconstriction assuming that we have normal fetal lung development normal surfactant production no there shouldn't be right so there should be no hypoxic assuming complete normal condition no hypoxic vasoconstriction and then the next thing here you have cut this cord so now these umbilical veins are no longer very significant for us we don't really care about these anymore right so what we can do is we can just say we're not really worried about these these are going to become another structure here in a second i don't really care about these

right now because these are no longer my focus okay so i'm just going to get rid of those they'll become something else a little bit later and we'll talk about what that is but let's go to those two structures that we had before one of the structures we have to draw this again because now you might think oh well if things were going from the right side to the left side well then technically blood would now shift technically if the pressure if the left pressure is now greater than the right pressure then technically wouldn't the

blood go in the opposite direction of the foramen ovale no watch watch what happens this is why you need to know that kind of anatomy of that atria interatrial septum so imagine here i draw that again all right here's our septum intermedium what did we have coming down here this was our septum primum then we had our osteum secundum then we had our septum secundum when blood is going from the right atrium to the left atrium it can go kind of like imagine this is like a valve is the best way to think about it

if i want blood to go this way it can but if i want blood to go back in this direction because of the way this actual interatrial septum is formed and the way it's actually made blood will not be allowed to go in this direction it'll kind of shut that valve closed so imagine here you kind of imagine this is like a like a like a lever you push blood here it's going to kind of start doing what smacking against that one and now can blood get through that tiny little space now no so blood

won't be going back to the right atrium from the left atrium because the left side pressures are higher than the right side pressures that's the first thing to remember okay that's interesting so what we were able to say is that the blood cannot go from the left side to the right side and you know what actually is even interesting eventually that hole the foraminal valve and normal patients normal fetus it should actually completely close so it should close what was that hole again it was previously called the foramen ovale generally it should close once birth

happens left pressure becomes higher than right pressure kind of starts causing fibrosis of that area and then switches it into a fibrotic area called the fossa ovalis so now no blood should be able to go either way between the atria that's important to remember okay good so now we understand that the second thing that we should understand follow the blood flow to the to the pulmonary circulation right for a second think about this if you now have more blood that's able to run through those pulmonary vessels because there's more oxygen now what's going to happen

to the blood flow running through these pulmonary arteries it's going to start increasing right because now these pulmonary vessels are no longer clamped down they're going to be nice and open and plump and blood is going to start rushing through these and they're going to run through the pulmonary arteries and they're going to run through the capillaries and they're going to come back via the pulmonary veins and you know the pulmonary veins right we're going to put p v these pulmonary veins where do they empty into the left atrium so now we have the blood

kind of nicely coming in here to that left atrium what did we say what's going to happen with that left atrium it no longer can go back we have fibrous tissue here now that's called the fossil valves no blood can go between the atria now so now the only direction it can really go here is into the left ventricle and then from the left ventricle what will happen it can move up via the aorta now as it moves up through the aorta through the ascending aorta and gets up to the aortic arch so we're going

to have aorta here go back to this next structure what was this structure here called it was called jor ductus arteriosus think about the pressures now when you think about the pressure between the pulmonary circulation so this is palm circulation and compare it to the aortic circulation which one's higher the aortic circulation right because that left sided pressures are going to be higher so where would blood actually kind of want to go it would want to go from the aorta into the pulmonary circulation and it'll do that for a very small amount of time to

keep pushing more blood into that pulmonary circuit so that we can get nice amounts of blood there to oxygenate the blood for the baby but you know what happens that ductus arteriosus is very stingy that's a good thing it's stingy so again what was this here structure called ductus arteriosus let's talk about this structure for a second because it's very important the ductus arteriosus is very sensitive to three things so here's our ductus arteriosus it's very sensitive to low oxygen or oxygen in general let's just say it's very sensitive to oxygen it's very sensitive to

prostaglandins okay so we'll put prostaglandins and it's also sensitive to what's called brady kinans whenever the baby is actually born right and it's breathing in oxygen what happens that goes up you know what happens whenever you have high oxygen it's inversely related to the prostaglandins you know prostaglandin is due to the ductus arteriosus high prostaglandins keep this ductus arteriosus patent and open and then low oxygen also keeps this ductus arteriosus patent and open as the oxygen concentration increases now the ductus arteriosus is going to become less patent as oxygen starts increasing guess what happens to

prostaglandin production it starts dropping so now the prostaglandin production will start dropping and then you know what happens whenever you have blood flow going through the lungs there's more bradykinin production whenever blood is flowing through the lungs more and now bradykina production will increase whenever bradykinin production increases guess what that also does all of these things whenever there is decreased prostaglandins increase oxygen and increase bradycains it closes the ductus arteriosus so now no more blood can be circulate going between the pulmonary and between the pulmonary artery and the aorta we want to kind of close

it off and keep them separate so now the ductus arteriosus after birth will start closing and no blood will be shunting between the pulmonary trunk and the aorta so now the aorta there might be a little bit of blood that flows in there during the process after birth but eventually that ductus arteriosus is going to close and blood will go on its own through the aortic circulation and blood will move on its own via the pulmonary circulation right now blood is still going to be coming right so umbilical veins going to get cut right so

now no blood's coming through that umbilical circulation but the baby's still getting blood that's coming from its lower limbs via the iliacs and via the inferior vena cava and that's emptying into the right atrium blood's still coming from the upper extremities and from the head and the neck coming down via the superior vena cava and when blood comes into that right atrium where will it go again that hole is closed it's not going to go between the right atrium to left atrium because that it's a fossil ovals now no hole there it only can go

into the right ventricle right ventricle then pumps up via the pulmonary trunk into the pulmonary trunk and then into the pulmonary arteries because this is now closed now we've separated the circulations perfectly because of this amazing process of the hypoxia vasoconstriction and then this ductus arteriosus sensitivity of oxygen prostaglandins and bradykinans the next question is is what happens then is as the blood is continuing to flow down let's go back to the aorta blood's coming down this actual aorta descending aorta going via the common iliac arteries right and the common iliacs you have the if

i put a line there you have the external iliacs and then you have your internal iliac arteries and then coming off of the internal iliac artery as your umbilical arteries again we cut the cord so now the umbilical arteries aren't going to be taking blood to the placenta anymore so they're going to start degrasing and becoming fibrotic tissue the umbilical veins they're not going to be taking blood to the actual inferior vena cava anymore so they're going to start degrading it's actually becoming fibrotic tissue the ductus arteriosus it'll actually close become kind of fibrotic tissue

and become another's particular structure that is the next thing that we have to address we understand now the whole fetal circulation process before and after birth now let's talk about what some of these actual structures umbilical vein umbilical artery ductus phonosis ductus arteriosus we already kind of mentioned the foraminal valve we'll do it again and then one other structure in the umbilical cord called the elantois become in the adult all right ninja nerds now let's kind of just have our nice little kind of finishing point kind of a little bit of a recap but also

just kind of making sure that you guys have a nice little way to remind yourself or outline what was the the big takeaway between the fetal structures and then the adult remnants if you will all right first thing ductus venosus again what was it just to remind you what was that connection between umbilical vein and inferior vena cava right this ductus venosus should close and when it closes it becomes the ligamentum venosum the ligamentum venosum the foramen ovale what was that structure between the right atria and the left atria it was formed by remember you

had the septum primum hole up in the top osteum's conundrum septum coming down is the septum secundum the little space through that is called the foramen ovale it should close after birth because of that changes in the left atrial pressure becoming higher than the right atrial pressure and smashing those structures together and it becoming fibrotic and becoming the fossa ovalis it's important to remember that because what happens is is if the foraminal vowel does not close okay it can become what's called the patent foramen ovale why is that an issue it could be like no

problem some people have them and have no issue but let's say that you have a dvt in your like in your lower leg it breaks off comes up the inferior vena cava goes into your right atrium where could it go potentially right atrium into left atrium via this patent foraminal vowel from the left atrium down to the left ventricle left ventricle up through your aorta where does the aortic carotids up into your brain you can develop a stroke it's called a patent foraminal bat vowel which can lead to what's called a paradoxical embolus so you

see how why that could be important to remember and the next thing is called the ductus arteriosus it was that little structure that was sensitive to what three things oxygen prostaglandins and brady kindness when it was generally connecting the pulmonary trunk and the aorta but as the oxygen concentration increases prostaglandin production decreases and bradykina production increases what happens to it it becomes closed and becomes a particular structure called the ligamentum arteriosum arteriosum if this sun of a gun does not close it can become the patent ductus arteriosus which is a type of a cyanotic congenital

heart defect right and that can be a problem and you'll be able to hear that usually in exams they'd love to say it's the machine continuous machine sounding type of murmur but again that is if it does not close it becomes the patent ductus arteriosus or pda all right so the umbilical vein again remember what is it doing it's taking oxygenated blood from the placenta via the umbilical cord emptying it into the shunt between that and the inferior vena cava which was called the ductus venosus you cut the cord it starts to degenerate and what

does it become it becomes a very interesting ligament that connects on the liver and that is called the ligamentum teres ligamentum teres and sometimes you know this ligament can reopen sometimes if you have really high uh portal pressure and hepatic uh portal and what's called portal hypertension from liver diseases and things like that the actual there has to be some direction for the blood to flow sometimes this can recantalize and blood can flow through it and then cause distension in some of the veins on the uh abdomen called capic medusae so again interesting kind of

structure there umbilical arteries there's two of these right now umbilical artery and elan choice this is this is why i mentioned the elantris because sometimes this comes up on exams and i had a heck of a time trying to remember which one was medium and mediol it's it's a son of a gun to thing to remember so here's how i like to remember it umbilical right there's two of them and there's al so media al umbilical ligament is the adult remnant of the umbilical artery okay so i just remember medio umbilical ligament okay now there

is another thing that it can become a lot of books will actually write this some small portion of the umbilical artery some of will become the media umbilical ligament but some portions of it can actually remain patent and actually provide blood flow from the internal iliac to the bladder and this is called so it also can give way to the superior vesicle artery beautiful so again i like to just remember a l medial there's two umbilical arteries plural that's the best i can do to help you to remember that all right so the last structure

i want to mention here because we haven't talked much about it in this situation but the atlantos right the answer is if you would actually take a cross-section right of the umbilical cord and look at it we already kind of mentioned some of these structures one of them if you took a cross section would be running here we're going to represent it here in this color here just for simplicity the umbilical vein even though it is carrying oxygenated blood okay this would be an umbilical vein then what else do you have here you have the

two umbilical arteries so these are your two umbilical arteries the next thing that you also have running around here is the elantois and sometimes what's called the vitalin duct and then there's also tiny little vitellin arteries we already talked about the vascular system and there's already small little vital and veins there's vital arteries and vital and veins that are also running in these areas now generally these will start to break down okay but it is important to know what the land choice becomes oh one other thing last thing i promise is there's also a jelly

here that comes around this area sometimes they like to ask this this jelly that's kind of all around the structure this is called wharton's jelly it's just designed to provide a little bit of like insulation okay and and what happens is after the baby's born the warren's jelly kind of likes actually starts kind of uh breaking down but again this is kind of the structure in the cross section what i want you to remember is the atlanta toys becomes particularly what's called the uracius and then the uracus eventually becomes fibrotic and becomes the median you

only have one elantois median whereas you have two umbilical arteries pleural medial umbilical ligament the elantois will become the median umbilical ligament i think we beat a dead horse with that one but as long as you guys don't mix these up that's the whole goal all right that covers fetal circulation all right ninjas in this video we talk about fetal circulation i hope it made sense and i hope you guys enjoyed it all right engineers thank you and as always until next time [Music] you