lastly and this isn't in your book this is something I did want to bring up because your case study will deal with this a little bit in fetal circulation so we've talked about how blood moves through a normal adult human it starts off coming back to the the right side of the heart right atrium then down to the right ventricle out to the lungs through the coronary arteries or start pulmonary arteries left and right goes to the lungs becomes oxygenated returns on the pulmonary veins into the left side of the heart left atrium then left ventricle and then out the aorta to systemic circulation in in a fetus in a developing baby who's still inside the mother it receives its oxygenated blood not from the lungs like a normal individual can breathe but from the umbilical cord that means that and here we're just showing here is the placenta that's interfacing with the maternal blood supply it brings in oxygenated blood down the umbilical vein it goes to the liver and then from the liver it makes its way to the heart so this is the oxygenated blood that's coming from the maternal circulation normally blood entering into the right side of the heart is deoxygenated so it gets sent to the lungs to be reoxygenate 'add in a fetus there is no breathing taking place the lungs aren't doing anything there's no oxygen there so it wouldn't make any sense to send the majority of the blood to the lungs majority of the oxygenated blood to the lungs so in fetal circulation there are two main adapt ations or two main structures that exist that allow for oxygenated blood that's already in the left side of the heart to pass to the right side of the heart and then out to systemic circulation these two areas are the the oval foramen or foramen ovale this is a hole a kind of a passageway between the the left and right atrium in a normal individual that is not there it's closed off but in a fetus it is there's this little hole and a valve a flap there so this allows for the oxygenated blood that's coming from mom to pass from the right atrium to the left atrium down to the left ventricle and out to systemic circulation instead of the majority of this oxygenated blood first going to the lungs that don't have any oxygen to to deliver to take or to push to the to the blood so then we get a smaller a small tiny amount of blood going to the lungs the majority gets passed to the left side of the heart so this is this structure is called the foramen ovale also in the pulmonary trunk right here there is what's called the ductus arteriosus so normally in a healthy adult individual the pulmonary trunk branches into the left and right pulmonary arteries they go off to the lungs again there's no oxygen in the in the lungs so there's no need teleologically for that blood to go to the lungs there's nothing to pick up there so this little ductus arteriosus 'm allows for the majority of the blood pumped by the right side of the heart to actually just get pumped directly into the aorta so we have two little bypasses here the ductus arteriosus 'm and the foramen ovale after an individual is born they take a big deep breath and that affects the lungs causes the blood vessels to dilate to get bigger and that decreases the resistance to those tissues so now it's really easy for blood to flow to the lungs that actually ends up shutting this valve so because the resistance goes down now there's less pressure pushing over this little valve closes and closes almost permanently for for the majority of individuals eventually it will kind of scar over and will left with and we're left with this bit of scar tissue which is called the fossa ovalis so that usually scars up additionally the ductus arteriosus 'm once oxygen increases in the blood will basically do the same thing this will start to deteriorate and turn into scar tissue and that closes off for most individuals so now we have our normal sort of adult circulation in some individuals though this foramen ovale stays open as well as the ductus arteriosus 'm so that can cause some problems and we'll see that in the key study