Main content
Health and medicine
Course: Health and medicine > Unit 2
Lesson 11: Fetal circulation- Meet the placenta!
- Umbilical vessels and the ductus venosus
- Hypoxic pulmonary vasoconstriction
- Foramen ovale and ductus arteriosus
- Fetal hemoglobin and hematocrit
- Double Bohr effect
- Fetal circulation right before birth
- Baby circulation right after birth
- Fetal structures in an adult
© 2023 Khan AcademyTerms of usePrivacy PolicyCookie Notice
Fetal structures in an adult
Find out what happens to those nifty fetal structures once we get older. Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.
Want to join the conversation?
- At, when PFO is mentioned, he says they can go on with their life without even knowing they have it. But is there anything that could possibly go wrong? If so, what? And is there a name for it? 5:17(13 votes)
- After a stroke is one of the times where you would investigate for a possible PFO. This is because a venous clot (like from a deep vein thrombosis you could get from a flight for example) can return to the right atrium, pass into the left atrium through the PFO and then be shot up into the brain via the aorta. This is also called a paradoxical embolism as the person above mentioned. If you are ever asked in an exam it's probably the main complication you should describe.(2 votes)
- can the patent foramen ovale turn in the fossa ovalis in late childhood/early adolescence?(5 votes)
- If it doesn't close properly you get what is called a shunt. Basically the blood flow from the body is avoiding going to the lungs like it did when the placenta took care of the breathing. (Not as much resistance, though.) But since the placenta is severed from the body, the baby develops cyanosis, which is bluish or purplish skin due to lack of oxygen ("blue baby syndrome"). It needs to close far before childhood or early adolescence, shortly before birth is best.(2 votes)
- Can the ligaments connected to your belly button ever cause any problems? It seems like they could pull on your liver or pull a way the blood source from your bladder in the case of an injury.(5 votes)
- How does the data that 20-25% of people have a patent foramen ovale?(2 votes)
- Both autopsy data and ultrasound data have found these numbers. Does that answer your question?(5 votes)
- I was just wondering what happens if we never form the Fossa Ovalies and hold on to the patent foramen ovale?
I was volunteering in a children hospital and I saw a case similar to that. I remember the baby's lips had a unique blue color. I asked one of the students and he mentioned one of the wholes in the heart wasn't closed properly (after watching this video I am guessing it might have been the Foramen Ovale or the ductus arteriosus). Also The baby had different blood pressures around his body so it wasn't a constant flow rate. This had cuased some of his organs to move out of its original spot and changes its shape.
Are these symptoms related to this condition when the Fossa Ovalis and the ligimintum artiosum are not formed properly?(2 votes)- A patent foramen ovale is a fairly common birth defect, but unless it's pretty severe, you don't typically see a lot of symptoms from it. Lots of people have them and they usually close when you get older, but even if they don't, they can be completely asymptomatic. Based on all of the symptoms you mentioned about the baby you saw, there was likely something else going on, since a PFO or PDA (patent ductus arteriosus) wouldn't cause that.(4 votes)
- The concept of PFO is fascinating. Could someone who develops an acute pulmonary oedema as a result of an infection (who has no seal just flaps) develop PFO in later life? Thanks(3 votes)
- Do the new ligaments have specific functions?(2 votes)
- If you are referring to the fetal structures that turn into "ligaments" they generally do not serve a purpose after birth.(3 votes)
- Could one make use of those ligaments in a surgical procedure? E.g. if somehow the normal circulation isn't functioning properly and one needs to bypass a certain area?(2 votes)
- they can catheterize the umbilical vein in babies after birth for fluid admission, blood test etc before they turn to ligaments. After they turn to ligaments there is no canal to catheterize(2 votes)
- So what may cause the belly button of some people to look big as the grow older?(2 votes)
- Could a PFO open if you go high altitude mountaineering (due to the low pO2)?(2 votes)
- A PFO might open in the presence of very high pressure in the right atrium. I'm not sure, low O2 might make the arterioles of the lungs constrict, increasing resistance and thereby increasing ventricular pressure needed to pump blood to the lungs.(1 vote)
Video transcript
So I left up this picture. This is a picture of how
blood flows in a baby right after it's born, and
all the different parts of that circulation and
all the different names. And the reason I left
this up is because I want to talk about
all the changes that then happen
as we grow older. So you know, let's take
myself for example. I'm an adult now. And as an adult, what are
all of the structures called? Or what becomes of all
these things in my body? Well, for starters, if I
look down at my belly button, I'm not going to see
a little smiley face. Right? I'm not going to see
any blood vessels. I'm just going to see skin. And that's because all these
blood vessels have really, for a long time in my body,
not been delivering blood. So that's the first kind of
change I want to point out. Now, what used to be the
umbilical vein over here has, in my body,
become a ligament. All of that, from
many years ago, there was some clotted
blood in there. But over the years-- in
fact, shortly after birth, this started getting fibrosed. And lots of tissue kind
of fell into this area, and it became almost like
what happens with a scab. You get lots of
proteins in there. And you don't really have
a space anymore for blood to flow. So this becomes a ligament. In fact, there's a
ligament that extends towards the portal vein. And even the ductus
venosus, that becomes a ligament as well. So all these become ligaments. In fact, they have
fancy Latin names. So let me actually just
replace this umbilical vein with what it's
called in my body. And in my body we call it
the ligamentum teres hepatis. So if you want to impress
your friends, you can say, ah, do you mean my
ligamentum teres hepatis? And that's what becomes
of the umbilical vein. This is actually kind of
a tricky word to remember. But "hepatis" refers to liver. So you know that this is
headed towards the liver. So you can remember it that way. And over on this side,
this ductus venosus, well, it's no longer a
duct, right? "Duct" implies that you can actually
pass something through it. And the way I've drawn it,
it's a ligament, right? So it's a ligament. And we're actually going to
name it something fancy as well. We'll call it
ligamentum-- so kind of starting out the same
way as the other one. This one is ligamentum venosum. So remember it used
to be ductus venosus. So now we call this
the ligamentum venosum. So that's fairly
easy to remember. So two ligamentums
so far, right? And I promise you we're going
to have a few more before we're done. Now moving on, we have blood
entering the right atrium. And you know blood
in the fetus used to go from the right
atrium to the left atrium through the foramen ovale. But then we talked
about how it closes when the pressure
on the left side gets higher than the
pressure on the right side. And so when it closes, the
idea is that, over time, there is actually going to be
some-- some tissue is going to basically form
between those two flaps. And so it actually
creates a real seal. And when that happens, then
that space-- this space right here-- becomes known
as the fossa ovalis. So that's what it might be
called in me or you today. If you were to actually look
inside of the right atrium, you would spot a
tiny little hole on the wall that has
tissue on the other side, and that's called
the fossa ovalis. But it turns out
that in many adults, you actually don't
have a real seal there. So the way I've drawn it
where there's actually a little seal between the
two, that may not even happen. In fact, let's say in
about 20%, or sometimes you'll see the
number 25% of adults, you actually just
have two flaps that could theoretically kind of move
apart from each other again. And so if you're one of those
20%, let's say 20 to 25%, if you're one of
them, then you'd have what's called a
patent foramen ovale. And if you're part
of the majority, then, the other 75 to 80%,
then you'd have a fossa ovalis. So really all that means
is that some people have a real seal that connects
the two flaps of tissue, and some people
don't have a seal. And so the two
flaps can actually move apart from each other if
the pressure on the right side gets really high. So in a person with a patent
foramen ovale, theoretically, if you had a lot of pressure on
this right side, on that spot, you would actually
open that flap up. And you could actually
have a situation like this, where all of a
sudden now, you can actually move blood between the two. So this is actually an
interesting thought process. You can actually move
blood from the right side to the left in people
with what they call a PFO. But for most people, the
pressure on the right side really never gets that high. So even if you have a
PFO, because the pressure on the right side
is almost always lower than the left
side, it almost always means that this
flap will stay shut. So even with a PFO, the
vast majority of people never even know it. In fact, they go on living
their lives very happily, even though there's really no
seal sealing that thing off. Now moving onwards, we
have the ductus arteriosus. And so we know that this,
shortly after birth, is going to kind of tighten up. The muscles constrict when
they face all those high oxygen levels and they can sense
the low prostaglandins. And this ductus
arteriosus then, it really doesn't have this name anymore. It gets changed. And in an adult, I'm
going to give you a moment to guess
as I write it out. Again, ligamentum-- and
I'll give you a clue. Try to remember what we
called this guy over here. We're going to call this
one ligamentum arteriosum. So you're getting the hint
for how we name these things. And now if we follow the
blood down, down, down, down the aorta, it goes into
the internal iliac artery. That's this guy on the left
and this guy on the right. And the internal iliac
artery has lots of branches. And we haven't drawn all the
branches, but there are many. And eventually, it
was going to lead into what we used to call
the umbilical artery. Now, these umbilical
arteries, just like the ductus
arteriosus, actually starts kind of constricting
once the oxygen levels go up and once the prostaglandins
levels go down. And when it constricts,
it turns into a ligament. And this is also
because there's no blood flow through this area. And the last place where
there is blood flow is going to maintain blood flow. So there were branches, I said. And of course, through
these branches, blood is flowing to
other areas, right? Blood it's going to, let's say,
different structures inside of our pelvis. And these last couple
of branches right here, these are headed
towards our bladder. So sometimes you'll see that. You'll see that
they'll say part of it turns into an artery
towards the bladder. And the other part
turns into a ligament. So let's actually erase this
word, "umbilical artery," and replace it with
the correct word, which is that it turns
into the medial-- and actually, this is very
important, because people get confused on this
point all the time. I'm going to point to the L--
medial umbilical ligament. And there are two of
them, of course, right? Because there are two arteries. So I should write medial
umbilical ligaments, two of them. So then just to
kind of summarize, we have a few ligaments down
here by our belly button. We have one important
ligament that's in our liver. We also have one up by
our aorta separating it from the pulmonary artery. And finally, we have-- either
you have a sealed-off version, and we call that a fossa
ovalis in our heart, or you have a patent
foramen ovale. And even if that's the
case, for most of us, that is not a problem.