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Studying for a test? Prepare with these 12 lessons on Advanced circulatory system physiology.
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before the baby is born there lot of adaptations that we see that allow the baby to take nutrients and oxygen from mom and inner successfully get those nutrients and oxygen to the different cells that need them in the body so what I want to do is kind of drying out for you and one diagram all the kind of things that we see this for birth these are all the things that are happening while the baby is still in the uterus sometimes we say in utero before birth what do we notice while this structure over here this is our placenta this is you know partially mom in partially fetus to the placenta has moms blood kind of pulling in this area and the baby actually sticks its little capillaries inside of the pool of blood and you can see that the purple ish blood is kind of going into the reddish blood is coming out and essentially what I was trying to draw there's that oxygen is getting picked up it's actually getting oxygenated in this blood as its kind of reddish is joining into this blood vessel down here this is kind of the smiley part of our Scarface and this is our umbilical vein their umbilical vein is as you get a carry oxygen blood back towards the liver area so let me just jump that name down umbilical vein and this is actually the first of the adaptations I was talking about so I'm gonna make a little list of adaptations over here on the side just so we can keep track of what they are adaptations and the first one will be the umbilical vein so once the blood goes into the umbilical vein it has kind of a branch point you can see that it can either go to the right or the last and if it goes to the left it's going to enter the liver so it goes kind of this way it's going into the liver and it's gonna take awhile for that blood to come out on the other side because it has to go through all the little capillaries in the liver and then emerged on the other side but there is a shortcut so the shortcut to me just circle is here the shortcut is actually going to be right here so let me just make sure it's very clear that shortcut keys this is called are docked dis the gnosis ductus witnesses and the doctors have been OSIS is basically get all our blood to go from the umbilical vein through it so it's like a little tube so it is just like any other blood vessel gonna go through it and on the other side it hits and meets up with are inferior vena cava so this is our inferior vena caval alright IVC just four short and the IVC inferior vena came as a large main pic near blood from the right leg and also from the left leg this down here to the inferior vena cava meets up with the blood coming from the umbilical vein which is very oxygenated and so this blood draws kinda purplish now because it's kind of got some option but it's not as rich as what was coming up initially from the umbilical vein is it mixed in with the IVC and that blood dumps into the right atrium is already among the side and simultaneously you actually have blood from the superior vena cava or SEC is our head and arm region raining down this way and his blood also ends up in the right atrium you've got this blood kind of mixing and now I'm gonna drive is kind of a deeper purple because it's mixed up blood now the second adaptation then let me just make sure I don't skip out on these this is the first time the 2nd law and would be the ductus the notice that I rode up which is as i said Thomas shortcut from the umbilical vein over to the inferior vena cava now the blood is in the right atrium so has a couple of options first it could simply go down into the right ventricle and some of the blade does that it just goes right down into the right ventricle LV goes into the right ventricle its gonna get squeezed it went to get squeezed it goes into the pulmonary artery the artery over here and we know that he has a branch over to the lungs on both sides so we've got some blood going to one lung and some blood going to this other longer but remember one step blood kind of approaches the lungs we have to think about what's going on inside of the lungs let me draw what's happening then inside the lungs you've got these socks air sacs actually are not full of air right because when the baby is still inside of the uterus or when the fetus in the uterus it's full of fluid you've got these sacks fluid in going past them are little blood vessels so this is a little blood vessel let's say this is an arterial over here now if it's full of fluid that means there's not much oxygen so what ends up happening is that there's a process called hypoxic pulmonary vasoconstriction and what that means is that the alveolus literally tries to help constrict constrict the arterioles so they are still has some smooth muscle like this and because there's no oxygen the alveolus is going to cause that little are chiral to basically can track down so basically looks a little bit more like this it looks like that what we've essentially done this increase the resistance of the DART rail and if this is happening millions of times and millions and millions of alveoli then the entire lung is gonna have a lot of resistance lot of resistance in the lung at this point so if that's the case that there's a lot of resistance then a few things we have to kind of deduce from that the first is that if there's a lot of resistance than the pressure in the pulmonary artery from this is our pulmonary artery right here these two little arrow to both of them the pressure in the pulmonary artery is gonna go very high so these pressures are going to be high and that's simply because you've got a lot of resistance that you have to try to fight against so they have a lot of pressure and it is a lot of pressure in the pulmonary artery just think back and think what where did that come from it came from the right ventricle so for there to be forward flow of blood you better have a lot of pressure on the right ventricle and then I could take the arguing back and say well if you have a lot of pressure the right ventricle then you must have a lot of pressure in the right atrium they have a lot of pressure basically on the right side of the heart because of the fact that you've got a lot of resistance in the lungs so these pressures especially the right atrial pressure starts getting so high that it starts getting higher than the pressure in the left atrium and see you get a little bit of blood slow that starts going from the right atrium across that for Raymond over that allows race here that allows blood actually go across it this is our freemen of alle Moreno Valley allows blood to go from one atrium over to the other instance blood can now go across your gonna see some of the blood continue down into the right ventricle but some of the blood will also come to go across into here and that's actually quite useful because at the same time the young blood going across you actually don't have too much blood coming back through the pulmonary veins and the reason for that again is because it's hard to get blood flow through the lungs because they're so much resistance there so you have a little bit of blood kinda coming in through the pulmonary veins and you get some blood coming from the right atrium now from the last 8 a.m. blood is gonna go down into the left ventricle and its gonna get squeezed around into the aorta get blood in the order I get squeezed there were sent there from the aorta from the left ventricle apologized so the left ventricle squeezing blood down into the aorta and the airport is distributing blood all the way down before I finish off showing you where the aortic blood goes that's actually make sure I don't forget my list over here my seared adaptation then should be there for a little valley foramen ovale scenting blood from the right atrium to the left atrium and a fourth adaptation siad just sketched out but haven't talked about is right here so you actually have this little this little guy right here a little connection little vessel you can think what is a vassal because blood flows through there between the pulmonary artery and aorta so this thing right here is called the ductus ductus arteriosus doctors arteriosus so the ductus arteriosus allows blood to go from the pulmonary artery to the aorta and why would blood going that direction particular will remember the pulmonary artery again has very high pressures and high pressures are because of the high resistance in the lungs so because of those high pressures blood of course goes from high pressure to a place where there is a lower pressure usually and in this case is gonna go from the pulmonary artery over to the aorta so that's going to flow in this direction of me just draw a little arrow it's gonna go for slowing in that direction so ductus arteriosus is another another vehicle adaptation so we've got four so far doctor Sartorius and this actually explains then why you don't get too much blood coming back through the pulmonary veins because a lot of the blood goes into the pulmonary artery trunk ends up going into the aorta now she doesn't even go into the lungs because the resistance is so high so now it's kinda wrap this up let's say blood is now down to the airport as I said it's going to go into the legs and it's also going to kind of go into these internal iliac arteries have drawn these arteries here is the internal iliac arteries and there of course lots of branches off the internal iliac but the important brandt said I want to play out right now is this one this branch this major sketching in this is actually the we have a name for we call this the umbilical artery so this is actually bringing blood back towards the placenta now why would so much blood go to the placenta me that's a fair question why doesn't it go you know there's a branch it goes to the bladder there's a bridge that goes other places why is blood going into the press center branch or the umbilical artery why why so much well it turns out that the placenta and this is very clever actually has a very low resistance very low resistance so just as the alongs have a high resistance and they're kind of making blood diver away from them the placenta has a low resistance and it makes blood divert towards it so you can see now that this is a really ingenious current system we have these five adaptations umbilical vein umbilical artery now we have the ductus arteriosus and we have the foramen ovale and the ductus arteriosus I don't miss out on any of them so we have five important adaptations here and this is how blood flows in the fetus