Fetal circulation right before birth | Circulatory system physiology | NCLEX-RN | Khan Academy
Summary
TLDREl guion del video describe el proceso de adaptación fetal antes del nacimiento, centrándose en cómo el bebé obtiene nutrientes y oxígeno de la madre. Se destaca la función de la placenta y el intercambio sanguíneo entre madre e hijo. Se mencionan cinco adaptaciones clave: la vena umbilical, la arteria umbilical, el ductus venosus, el foramen ovale y el ductus arteriosus. Estas estructuras permiten que la sangre oxigenada fluya directamente al corazón y se distribuyan a los órganos importantes, mientras que la sangre de bajo oxígeno regresa a la placenta para su procesamiento. El guion ilustra cómo la resistencia en los pulmones del feto y la baja resistencia en la placenta influyen en la dirección del flujo sanguíneo.
Takeaways
- 👶 Antes del nacimiento, el bebé tiene adaptaciones para obtener nutrientes y oxígeno de la madre.
- 📐 El placenta es una estructura mixta que permite el intercambio de nutrientes y oxígeno entre la madre y el bebé.
- 🔄 La sangre del bebé se oxigena en el placenta y se mezcla con la de la madre a través de capilares.
- 🌀 La vena umbilical es la primera adaptación clave que transporta oxígeno y nutrientes al hígado del bebé.
- 🚀 El ductus venosus es un atajo que permite que la sangre del vientre del bebé pase directamente a la vena cava inferior.
- 🔄 La vena cava inferior recolecta sangre de las piernas y mezcla con la sangre oxigenada proveniente de la vena umbilical.
- 🫀 La presión en el lado derecho del corazón es alta debido a la resistencia en los pulmones del bebé.
- 🗝️ El foramen ovale permite que la sangre fluya del atrio derecho al atrio izquierdo, evitando la necesidad de pasar por los pulmones.
- 🔄 El ductus arteriosus es una conexión fetal que permite que la sangre fluya desde la arteria pulmonar a la aorta.
- 🌐 La aorta distribuye la sangre oxigenada a lo largo del cuerpo del bebé, incluyendo las piernas y el placenta.
- 🔙 La arteria umbilical es una rama importante de la aorta que devuelve la sangre al placenta, donde tiene baja resistencia.
Q & A
¿Qué es la placenta y cómo ayuda en el intercambio de nutrientes y oxígeno antes del nacimiento del bebé?
-La placenta es una estructura parcialmente del mamífero y parcialmente del feto que permite que el bebé obtenga nutrientes y oxígeno de la madre. La sangre de la madre se acumula en una zona de la placenta y el bebé inserta sus capilares en ese charco de sangre para intercambiar nutrientes y oxígeno.
¿Cuál es la función del ductus venosus durante el desarrollo fetal?
-El ductus venosus es un atajo sanguíneo que permite que la sangre proveniente de la vena umbilical se una directamente a la vena cava inferior, evitando el paso por el hígado y asegurando que la sangre oxigenada llegue rápidamente al corazón del feto.
¿Cómo se describe la mezcla de la sangre oxigenada y la no oxigenada en la atrium derecha del corazón fetal?
-La sangre oxigenada proveniente de la vena umbilical se mezcla con la sangre proveniente de las venas cava superior y inferior en la atrium derecha. Esta mezcla resulta en una sangre de color púrpura más oscuro, indicando una mezcla de sangre oxigenada y no oxigenada.
¿Qué proceso ocurre en los pulmones fetales que resulta en una mayor resistencia y cómo afecta esto a la presión arterial?
-El proceso de hipóxica pulmonar vasoconstrictión ocurre en los pulmones fetales, lo que hace que los arteriolas se contraigan debido a la falta de oxígeno. Esto aumenta la resistencia en los pulmones y, consecuentemente, la presión en la arteria pulmonar se eleva.
¿Cuál es el propósito del foramen ovale en el corazón fetal y cómo ayuda en el flujo sanguíneo?
-El foramen ovale es una abertura en el septum interauricular del corazón fetal que permite que la sangre fluya del atrio derecho al atrio izquierdo. Esto ayuda a que la sangre oxigenada llegue directamente al ventriclo izquierdo y luego a la aorta, evitando el pulmón donde la resistencia es alta.
¿Qué es el ductus arteriosus y por qué es importante para el flujo sanguíneo fetal?
-El ductus arteriosus es un conducto que conecta la arteria pulmonar con la aorta en el corazón fetal. Permite que la sangre con presión alta proveniente de la arteria pulmonar fluya hacia la aorta, evitando así el pulmón donde la resistencia es alta.
¿Cómo se describe el flujo de la sangre en el aorta del feto y hacia dónde se dirige?
-La sangre proveniente del ventriclo izquierdo se dirige a la aorta, que luego distribuye la sangre a través del cuerpo del feto, incluyendo las piernas y los arterios internos ilíacos.
¿Cuál es el nombre de la arteria que lleva la sangre de regreso a la placenta y por qué es importante?
-La arteria umbilical es la que lleva la sangre de regreso a la placenta. Es importante porque la placenta tiene una resistencia baja, lo que hace que la sangre se dirija hacia ella para recoger más nutrientes y oxígeno.
¿Cuántas adaptaciones importantes se mencionan en el flujo sanguíneo fetal y cuáles son?
-Se mencionan cinco adaptaciones importantes en el flujo sanguíneo fetal: la vena umbilical, la arteria umbilical, el ductus venosus, el foramen ovale y el ductus arteriosus.
¿Cómo se adaptan estas estructuras fetales después del nacimiento del bebé?
-Después del nacimiento, las estructuras como el ductus venosus, el foramen ovale y el ductus arteriosus comienzan a cerrarse, ya que el bebé comienza a respirar y los pulmones asumen la función de oxigenación, reduciendo la necesidad de estas adaptaciones fetales.
¿Qué sucede con la resistencia en los pulmones después del nacimiento del bebé y cómo afecta esto el flujo sanguíneo?
-Después del nacimiento, los pulmones se llenan de aire y la resistencia disminuye significativamente. Esto reduce la presión en la arteria pulmonar, lo que provoca el cierre del ductus arteriosus y normaliza el flujo sanguíneo.
Outlines
🤰 Adaptaciones fetales antes del nacimiento
El primer párrafo explica las adaptaciones que ocurren antes del nacimiento para permitir que el bebé obtenga nutrientes y oxígeno de la madre. Se describe el papel de la placenta y cómo las capillarias del bebé se insertan en la sangre materna. Se ilustra el proceso de oxigenación del sangre y su flujo a través del vena yugular umbilical. Se mencionan las primeras adaptaciones: la vena yugular umbilical y el ductus venosus, que permite a la sangre omitir el hígado y unirse directamente a la vena cava inferior.
🫁 La importancia del hipoxia en el pulmón fetal
El segundo párrafo detalla cómo la ausencia de oxígeno en las alveolas del pulmón del feto provoca una contracción de los arteriolas pulmonares llamada hipoxia pulmonar vasoconstrictiva. Esto aumenta la resistencia en el pulmón, lo que lleva a un aumento de la presión en la arteria pulmonar y, por ende, en la ventrícula y atrio derecho. Como resultado, la presión en el atrio derecho supera la del atrio izquierdo, permitiendo que la sangre fluya a través del foramen ovale y se una con la sangre que proviene de la vena cava superior. Se discuten las consecuencias de esta adaptación fetal y cómo la sangre se distribuye a través del cuerpo del feto.
🔄 Adaptaciones fetales en la circulación sanguínea
El tercer párrafo concluye la explicación de las adaptaciones fetales, destacando cómo la sangre fluye desde la aorta hacia las piernas y el plexo placentario a través de la arteria umbilical. Se enfatiza cómo la placenta, al tener baja resistencia, atrae la sangre de regreso, en contraste con la alta resistencia de los pulmones que desvía la sangre. Se resumen las cinco adaptaciones clave: la vena yugular umbilical, la arteria umbilical, el ductus venosus, el foramen ovale y el ductus arteriosus, destacando su papel en la circulación fetal.
Mindmap
Keywords
💡Placenta
💡Umbilical vein
💡Ductus venosus
💡Inferior vena cava (IVC)
💡Foramen ovale
💡Ductus arteriosus
💡Hipoxia
💡Hipotensivo pulmonar
💡Aurícula derecha
💡Aorta
Highlights
Adaptations before birth allow the baby to take nutrients and oxygen from the mother.
The placenta is a crucial structure for nutrient and oxygen exchange between mother and fetus.
The umbilical vein carries oxygenated blood from the placenta to the fetus.
The ductus venosus serves as a shortcut for blood from the umbilical vein to the inferior vena cava.
The inferior vena cava (IVC) collects blood from both legs and mixes with oxygenated blood from the umbilical vein.
The right atrium receives mixed blood from the IVC and superior vena cava (SVC).
Hypoxic pulmonary vasoconstriction in the lungs restricts blood flow due to lack of oxygen.
Increased resistance in the pulmonary artery leads to high pressure in the right side of the heart.
The foramen ovale allows blood to flow from the right atrium to the left atrium.
Blood from the right ventricle is directed away from the lungs due to high resistance.
The ductus arteriosus shunts blood from the pulmonary artery to the aorta, bypassing the lungs.
The aorta distributes blood to the rest of the body, including the legs and internal iliac arteries.
The umbilical artery returns deoxygenated blood from the fetus back to the placenta.
The placenta has low resistance, drawing blood towards it despite the presence of other branches.
Five key fetal adaptations include the umbilical vein, umbilical artery, ductus venosus, foramen ovale, and ductus arteriosus.
Transcripts
Before a baby is born, there are a lot
of adaptations that we see that allow the baby
to take nutrients and oxygen from mom
and successfully get those nutrients
and oxygen to the different cells that need them
in the body.
So what I wanted to do is kind of draw out
for you in one diagram all the kind of things
that we see before birth.
These are all the things that are happening
while the baby is still in the uterus.
Sometimes we say in utero.
So before birth, what do we notice?
Well, this structure over here, this is our placenta.
This is partially mom and partially fetus.
So the placenta has mom's blood kind of pooling in this area.
And the baby actually sticks its little capillaries
inside of that pool of blood.
And you can see that the purplish blood is
kind of going in, and the reddish blood is coming out.
And essentially what I was trying
to draw there is that oxygen is getting picked up.
So it's actually getting oxygenated.
And this blood, as it's kind of reddish,
is joining into this blood vessel down here.
So this is kind of the smiley part of our face.
And this is our umbilical vein.
So this umbilical vein is actually
going to carry oxygen and blood back towards the liver area.
So let me actually just jot that name down, umbilical vein.
And this is actually the first of the adaptations
I was talking about.
So I'm going to make a little list of adaptations over here
on the side, just so we can keep track of what they are.
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 left.
And if it goes to the left, it's going to enter the liver.
So if it goes kind of this way, it's going enter the liver.
And it's going to take a while 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 emerge on the other side.
But there is a shortcut.
So the shortcut-- let me just circle it here.
The shortcut is actually going to be right here.
So let me just make sure it's very clear what
the shortcut is.
This is called our ductus venosus.
And the ductus venosus is basically
going to allow 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.
It's going to go through it.
And on the other side, it hits and meets up
with our inferior vena cava.
So this is our inferior vena cava.
I'll write IVC just for short.
And the IVC or the inferior vena cava
is a large vein picking up blood from the right leg
and also from the left leg.
So this is our left leg down here.
So the interior vena cava meets up
with the blood coming from the umbilical vein, which
is very oxygenated.
And so this blood I'm going to draw is kind of purplish
now, because it's kind of got some oxygen,
but it's not as rich as what was coming out initially
from the umbilical vein because it mixed in with the IVC.
And that blood dumps into the right atrium.
So this is our right atrium on this side.
And simultaneously, you actually have blood
from the superior vena cava, or SVC.
This is our head and arm region, draining down this way.
And this blood also kind of ends up in the right atrium.
So you've got this blood kind of mixing.
And now I'm going to draw it as 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 one.
The second one would be the ductus venosus,
that I wrote out.
Which is, as I said, kind of a shortcut
from the umbilical vein over to the inferior vena cava.
Now, the blood is in the right atrium.
So it has a couple of options.
First, it could simply go down into the right ventricle.
And some of the blood does that.
It just goes right down into the right ventricle.
And if goes into the right ventricle,
it's going to get squeezed.
And once it gets squeezed, it goes into the pulmonary artery.
This is my pulmonary artery over here.
And we know the pulmonary artery 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 lung.
But remember, once that blood kind of approaches the lungs,
we have to think about what's going on inside of the lungs.
So let me draw out what's happening then
inside the lungs.
You've got these sacs, air sacs, that
actually are not full of air.
Right?
Because when the baby is still inside of the uterus,
or when the fetus is in the uterus, it's full of fluid.
So you've got these sacs full of fluid.
And going past them are little blood vessels.
So this is a little blood vessel.
And let's say this is an arteriole 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 the arteriole.
So the arteriole has some smooth muscle like this.
And because there's no oxygen, the alveolus
is going to cause that little arteriole to basically contract
down.
So basically, it looks a little bit more like this.
And when it looks like that, what we've essentially done
is increased the resistance of that arteriole.
And if this is happening millions of times
in millions and millions of alveoli,
then the entire lung is going to have a lot of resistance.
A lot of resistance in the lung at this point.
So if that's the case, if 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,
then the pressure in the pulmonary artery-- remember,
this is our pulmonary artery right here, these two.
I'll actually draw a little arrow to both of them.
The pressure in the pulmonary artery
is going to 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 if there's a lot of pressure in the pulmonary artery,
just think back, and think, well,
where did that pulmonary artery come from?
It came from the right ventricle.
So for there to be forward flow of blood,
you better have a lot of pressure
in the right ventricle.
And then I could take the argument back and say, well,
if you have a lot of pressure in the right ventricle,
then you must have a lot of pressure in the right atrium.
So you 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 so you get a little bit of blood flow
that starts going from the right atrium,
across that foramen ovale, that allows-- right here-- that
allows blood to actually go across it.
So this is our foramen ovale.
Foramen ovale allows blood to go from one atrium
over to the other.
And since blood can now go across,
you're going to see some of the blood
continue down in the right ventricle.
But some of the blood will also kind of go across into here.
And that's actually quite useful,
because at the same time that you have 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 there's so much resistance there.
So you have a little bit of blood kind of coming in
through the pulmonary veins.
And you get some blood coming from the right atrium.
Now, from the left atrium, blood is
going to go down into the left ventricle.
And on its going to get squeezed around into the aorta.
So now you get blood in the aorta.
That gets squeezed there or sent there from the aorta--
or from the left ventricle.
I apologize.
So the left ventricle is squeezing blood
down into the aorta.
And the aorta is distributing blood all the way down.
Now, before I finish off showing you
where the aortic blood goes, let's actually make sure
I don't forget my list over here.
My third adaptation, then, should be the foramen ovale,
foramen ovale sending blood from the right atrium
to the left atrium.
And a fourth adaptation, actually, I've
just kind of sketched out, but I haven't talked about yet,
is right here.
So you actually have this little guy right here.
A little connection, a little vessel--
you can think of it as a vessel because blood flows
through there-- between the pulmonary artery and the aorta.
So this thing right here is called the ductus arteriosus.
So the ductus arteriosus allows blood
to go from the pulmonary artery to the aorta.
And why would blood go in that direction in particular?
Well, remember the pulmonary artery,
again, has very high pressures.
And the 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's lower pressure usually.
And in this case, it's going to go from the pulmonary artery
over to the aorta.
So it's actually going to flow in this direction.
Let me just draw a little arrow.
It's going to go flowing in that direction.
So ductus arteriosus is another fetal adaptation.
So we've got four so far.
Ductus arteriosus.
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.
It actually doesn't even go into the lungs
because the resistance is so high.
So now let's kind of wrap this up.
Let's say blood is now down in the aorta.
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.
So I've drawn these arteries here.
These are the internal iliac arteries.
And there are, of course, lots of branches
off the internal iliac.
But the important branch that I want to point out right now
is this one.
This branch, this major one that I'm
kind of sketching in, this is actually-- we
have a name for it.
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?
I mean, that's a fair question.
Why doesn't it go-- there's a branch here
that goes to the bladder.
There's a branch that goes to other places.
Why is blood going into the placental branch
or the umbilical artery?
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 lungs have a high resistance
and they're kind of making blood divert 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 kind
of system.
We have these five adaptations-- the umbilical vein,
the umbilical artery now, we have the ductus venosus,
and we have the foramen ovale, and the ductus arteriosus.
I don't want to miss out on any of them.
So we have five important adaptations here.
And this is how blood flows in the fetus.
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