Fetal Circulation (Before and After Birth) Maternity Nursing Heart Shunts NCLEX

Summary

This video explains fetal circulation and how it differs from normal circulation after birth. The instructor reviews the typical blood flow through the heart and highlights the key difference in fetal circulation, which involves three shunts that bypass the lungs. The fetus relies on the placenta for oxygen and nutrients, delivered through the umbilical cord. The video also covers how the circulation system changes after birth when the baby begins using its lungs, leading to the closure of these shunts. Viewers are invited to take a quiz to test their knowledge on the topic.

Takeaways

• 🌟 Fetal circulation is different from adult circulation because the fetus does not use its lungs for oxygenation.
• 🔄 The fetus relies on the placenta to exchange oxygen and nutrients, bypassing the need for lung function.
• 🚫 Three main shunts in fetal circulation are the ductus venosus, foramen ovale, and ductus arteriosus, which allow blood to bypass the lungs.
• 📍 The ductus venosus shunts blood from the umbilical vein to the inferior vena cava.
• 🔄 The foramen ovale allows oxygenated blood to flow from the right atrium to the left atrium.
• 🔗 The ductus arteriosus connects the pulmonary artery to the aorta, directing blood away from the non-functional lungs.
• 💧 The placenta acts as a temporary lung, providing oxygen and nutrients to the fetus and removing waste.
• 🌀 Blood flow in the fetus is directed to ensure the most oxygenated blood reaches the brain and other vital organs.
• 👶 After birth, the baby's first breaths cause the lungs to expand, changing blood pressure and closing the fetal shunts.
• 🛑 The closure of the foramen ovale and ductus arteriosus is crucial for the transition to independent respiration and circulation.
• ❗ Failure to close these shunts after birth can lead to congenital heart defects.

Q & A

What is the main difference between fetal circulation and normal postnatal circulation?

The main difference is that fetal circulation involves shunts to bypass the lungs, which are non-functional in utero, while postnatal circulation relies on the lungs for oxygen exchange.

Why does the fetal circulatory system bypass the lungs?

The fetal circulatory system bypasses the lungs because the fetus is not breathing air; its lungs are filled with fluid. Oxygen is provided by the placenta, so the blood is shunted away from the lungs.

What are the three main shunts in fetal circulation, and what are their roles?

The three main shunts are the ductus venosus, foramen ovale, and ductus arteriosus. The ductus venosus bypasses the liver, the foramen ovale allows blood to flow between the right and left atrium, and the ductus arteriosus connects the pulmonary artery to the aorta, bypassing the lungs.

What is the function of the placenta in fetal circulation?

The placenta functions as the site for gas exchange and nutrient delivery in fetal circulation, providing oxygen and nutrients from the mother’s blood and removing waste products from the fetus.

How does the umbilical cord contribute to fetal circulation?

The umbilical cord has one umbilical vein, which carries oxygenated blood from the placenta to the fetus, and two umbilical arteries, which carry deoxygenated blood back to the placenta for waste removal and reoxygenation.

What happens to the shunts after birth?

After birth, the shunts (ductus venosus, foramen ovale, and ductus arteriosus) close due to changes in pressure and the baby's need to use its lungs for oxygen exchange. The closure ensures blood flows properly to the lungs for oxygenation.

Why does the foramen ovale close after birth?

The foramen ovale closes after birth because the pressure in the left atrium becomes higher than the right atrium, reversing the flow of blood and eliminating the need for this shunt.

What role do prostaglandins play in fetal circulation?

Prostaglandins, produced by the placenta, help keep the ductus arteriosus open during fetal development. After birth, the removal of the placenta and the decrease in prostaglandins allow the ductus arteriosus to close.

What happens if the foramen ovale does not close after birth?

If the foramen ovale does not close after birth, it results in a condition called a patent foramen ovale (PFO), which can lead to abnormal circulation where blood may still bypass the lungs.

How does the resistance in the fetal lungs affect blood flow?

In the fetus, the lungs are filled with fluid, causing high resistance. This high resistance directs blood away from the lungs through the ductus arteriosus and the foramen ovale, ensuring that blood bypasses the non-functional lungs.

Outlines

00:00

🌀 Introduction to Fetal Circulation

Sarah Thread Sterner introduces the topic of fetal circulation, emphasizing the importance of understanding normal blood flow in the heart before diving into the specifics of fetal circulation. She explains that the fetal heart has shunts that direct blood away from the non-functional lungs, which are filled with fluid in utero. The video promises a quiz to test the viewer's understanding of the material after watching. The normal blood flow is reviewed, highlighting the journey of deoxygenated blood from the body to the lungs for oxygenation, and then to the left side of the heart to be pumped throughout the body.

05:03

🔄 The Role of Shunts in Fetal Circulation

The paragraph delves into the three shunts present in fetal circulation: the ductus venosus, the foramen ovale, and the ductus arteriosus. These shunts allow blood to bypass the lungs, which are not used for respiration in utero. The placenta, with the help of the umbilical cord, serves as the source of oxygen and nutrients for the fetus, acting as a temporary 'lung'. The umbilical vein carries oxygenated blood from the placenta to the fetus, while the two umbilical arteries return deoxygenated blood back to the placenta. The video explains how blood flow changes as the fetus develops and prepares for life outside the womb.

10:04

🚫 Bypassing the Lungs in Utero

This section describes how blood flow is directed in the fetal heart to bypass the lungs. The ductus venosus shunts blood from the umbilical vein to the inferior vena cava, while the foramen ovale allows oxygenated blood to flow from the right atrium to the left atrium. The ductus arteriosus shunts blood from the pulmonary artery to the aorta, ensuring that the majority of blood goes to the body rather than the non-functional lungs. The pressure differences between the right and left sides of the heart facilitate this shunting process.

15:04

🌱 Transition from Fetal to Postnatal Circulation

The final paragraph discusses the changes in circulation that occur after birth. Cutting the umbilical cord stops the transfer of blood between the fetus and the placenta. As the baby starts breathing and clears the fluid from its lungs, the resistance in the lungs decreases, changing the pressure dynamics in the heart and causing the shunts to close. The foramen ovale and ductus arteriosus close, transitioning the baby's circulation to the adult pattern where blood must flow through the lungs for oxygenation. The video concludes with a reminder to take the quiz to test knowledge on fetal circulation.

Keywords

💡Fetal Circulation

Fetal circulation refers to the unique blood flow pattern within a developing fetus, which allows the fetus to receive oxygen and nutrients from the mother's blood supply via the placenta. This process bypasses the lungs, as the fetus does not breathe while in utero. The video script explains how fetal circulation is different from the normal blood flow in adults, highlighting the role of shunts such as the ductus venosus, foramen ovale, and ductus arteriosus.

💡Shunts

Shunts in the context of fetal circulation are passages that allow blood to flow in different directions, bypassing certain parts of the circulatory system. The script mentions three key shunts: the ductus venosus, foramen ovale, and ductus arteriosus. These shunts are crucial for directing blood away from the non-functional lungs and ensuring that oxygenated blood reaches the baby's body.

💡Placenta

The placenta is an organ that develops in the uterus during pregnancy, providing oxygen and nutrients to the fetus and removing waste products. It is described in the script as the 'lifeline' for the baby while in the uterus, as it connects with the mother's circulation to facilitate the exchange of oxygen, nutrients, and waste.

💡Umbilical Cord

The umbilical cord is a cord that connects the fetus to the placenta, allowing for the exchange of oxygen, nutrients, and waste. The script explains that there is typically one umbilical vein carrying oxygenated blood from the placenta to the fetus and two umbilical arteries carrying deoxygenated blood back to the placenta.

💡Deoxygenated Blood

Deoxygenated blood is blood that has released its oxygen to the body's tissues and is in need of reoxygenation. In the script, deoxygenated blood is described as blood that has returned from the body to the heart, low in oxygen, and in need of replenishment via the lungs in a typical circulation system.

💡Oxygenated Blood

Oxygenated blood is blood that has been enriched with oxygen. The script mentions that oxygenated blood from the mother is carried to the fetus via the umbilical vein, rich in oxygen and nutrients, which is essential for the baby's growth and development.

💡Foramen Ovale

The foramen ovale is a shunt located between the right and left atria of the fetal heart. The script explains that it allows oxygenated blood from the umbilical vein to bypass the right ventricle and lungs, directly entering the left atrium to be pumped to the body.

💡Ductus Arteriosus

The ductus arteriosus is a shunt that connects the pulmonary artery to the aorta in fetal circulation. As described in the script, it allows blood to bypass the lungs by directing it from the pulmonary artery into the aorta, ensuring that the blood is oxygenated by the placenta rather than the non-functional fetal lungs.

💡Ductus Venosus

The ductus venosus is a shunt located near the liver and is responsible for directing oxygenated blood from the umbilical vein to the inferior vena cava, thus bypassing the liver and ensuring that nutrient-rich blood reaches the heart efficiently.

💡Gas Exchange

Gas exchange is the process by which oxygen is taken into the bloodstream and carbon dioxide is expelled. The script explains that in the fetus, this process occurs across the placenta rather than the lungs. After birth, the lungs begin to function, and gas exchange starts to occur there.

💡Postnatal Changes

Postnatal changes refer to the physiological adjustments that occur after birth. The script describes how the cutting of the umbilical cord and the baby's first breaths lead to changes in blood pressure and resistance in the circulatory system, causing the fetal shunts to close and the lungs to begin functioning for gas exchange.

Highlights

Introduction to fetal circulation and its differences from normal adult circulation.

Explanation of how the heart and lungs work together in a normal adult to oxygenate blood and distribute it throughout the body.

Review of normal blood flow through the adult heart, starting with deoxygenated blood from the body.

Importance of shunts in fetal circulation to bypass the non-functional lungs filled with fluid.

Introduction to the three fetal shunts: ductus venosus, foramen ovale, and ductus arteriosus.

Explanation of how the placenta functions as the temporary lungs for the fetus by providing oxygen and nutrients.

Discussion on the umbilical vein carrying oxygenated blood and the two umbilical arteries carrying deoxygenated blood.

Role of the ductus venosus in shunting blood from the liver to the inferior vena cava.

Importance of the foramen ovale in allowing oxygenated blood to bypass the right ventricle and go to the left atrium.

Explanation of how the ductus arteriosus connects the pulmonary artery to the aorta to bypass the lungs.

Details about how the pressure differences between the lungs and heart enable blood flow through the shunts in fetal circulation.

Changes in fetal circulation after birth: cutting the umbilical cord and the effects on ductus venosus, foramen ovale, and ductus arteriosus.

Discussion on how the pressure drop in the lungs after birth affects circulation and closes the shunts.

Description of patent foramen ovale (PFO) and its occurrence in some people when the foramen ovale fails to close.

The effect of decreased prostaglandin levels after birth on the closure of the ductus arteriosus.

Transcripts

hey everyone it's sarah thread sterner

sorry and calm and today we're going to

talk about fetal circulation and as

always whenever you get done watching

this youtube video you can access the

free quiz that will test you on this

content so let's get started to help us

understand fetal circulation we first

have to go back and review the normal

blood flow of the heart like we need to

know how the blood actually flows

through a heart that is outside of the

uterus that's not depending on a

placenta and we need to know where

deoxygenated blood is versus oxygenated

blood because the biggest difference

between a person's heart whenever

they're outside of utero compared to

whenever they're inside of utero is that

inside of utero they have these shots

that are shunting hints pushing away or

pulling away blood from the lungs

because in utero the person the baby is

not using their lungs they're full of

fluid

but whenever they're born they do use

their lungs

so those shunts aren't needed anymore

because we actually need that blood to

go through the lungs so first let's

review the blood flow through the heart

so everything starts on this right side

and here in this illustration in the

blue this is our right side and over

here this is our left side so what's

going on on the right side is that all

this blood is draining back to your

heart it is very low in oxygen because

that oxygen has went and replenished

your tissues and organs so they continue

to work so now it goes on to the right

side and it's whole goal is to get to

the lungs because the lungs are going to

replenish that deoxygenated blood with

oxygen and then after it does that it's

going to enter into the left side which

is going to pump it up through your body

and replenish your organs and tissues

with oxygen and it's just constantly

cycling like this so everything we have

this inferior vena cava in the superior

the vena cava and blood is draining back

to those the blood is going to go down

into the right atrium the

and it's gonna flow down into the right

ventricle the right ventricle is going

to pump it up through the pulmonary

artery right now it's still low in

oxygen but once it leaves the pulmonary

artery it's gonna hit the lungs where

gas exchange is going to happen

so the build-up of waste in your blood

like carbon dioxide is going to cross

over you're going to exhale that out and

the oxygen that you've taken in is gonna

cross over and go in the blood and

replenish it so over here I have the

deoxygenated represented in blue letting

you know it's really low in oxygen so

once I hit stop those lungs it's gonna

flow back through into the pulmonary

vein so now we're into the left side of

the heart and it's red it's really high

in oxygen so it's going to go into the

left atrium down through the left

ventricle which is really strong and

it's going to pump that blood up through

the aorta and it's going to shoot up

through here go to your brain your upper

extremities it's also going to flow down

through here through the descending

aorta and replenish your lower

extremities so as you can see the right

and left side they work beautifully

together but they really have their own

job the right side is going to take

deoxygenated blood pump it to the loans

the left side is going to take that

oxygenated blood it just receive from

the lungs and pump it throughout the

body so the heart and the lungs they

work beautifully together

now as you can see in this heart there

are no shunts or a little passageways

that's allowing blood to flow in

different directions which would help

bypass the lungs because we're using the

lungs so the lungs need this blood flow

so gas exchange can't occur now that is

what's different in this fetal heart

circulation here our lungs are not

working they're non-functional they're

full of fluid but whenever that baby is

born takes their first breath those

loans those Abiola sacs they pop open

baby starts breathing gas exchange

starts to occur however before that even

happens while they're still in utero the

lungs aren't work

so we need a little bit of blood flow to

go to those lungs to maintain that lung

tissue but we need majority of it to

bypass the lungs so to do that in the

fetal heart and in circulation we have

three shunts all of those three shunts

two shunts play a huge role with

shunting blood away from the lungs so

for exams you want to remember the names

of these shunts where they're located

and how blood flows through them so the

shunt I want you to remember are the

ductus venosus the foramen ovale and the

ductus arteriosus the ductus venosus is

located over here with the liver and

we're going to go in depth with these

here in a moment the foramen ovale is

located between the right atrium and the

left atrium and the ductus arteriosus

helps connect the pulmonary artery to

the aorta now you may be wondering okay

we're bypassing the lungs so the lungs

aren't providing oxygen to the blood but

this baby that's growing in the uterus

still needs oxygen in their blood so

their brain can develop and their whole

body and all those vital organs so how

are they getting oxygen in their blood

well they're getting it from the

placenta now the placenta along with the

umbilical cord which attaches to the

baby is like the lifeline for that baby

whilst developing in the uterus if you

don't have a healthy placenta there's

gonna be issues with the baby growing

and developing properly along with major

complications that can happen so the

placenta what it does is it embeds

itself in the uterus and when it does

this it in a sense connects with moms

circulation because this placenta what

it's gonna do is it's going to give the

baby oxygen and nutrients that it pulls

from Mom's circulation Cinda through the

umbilical cord go to baby and then

baby's gonna use it up produce its own

waste and it needs to get rid of it so

the baby will send it back through the

umbilical cord to the placenta which

will go into moms

circulation and mom will clear it so

think of the placenta as like the

temporary lungs for the baby until

they're actually able to use their own

set of lungs now for exams what you want

to know is really about this umbilical

cord specifically about the umbilical

vein and the umbilical artery like how

many there are of each and what type of

blood they carry so with this umbilical

cord there's usually in most babies

there is only one umbilical vein and

what this umbilical vein does is it

carries oxygenated blood so it's gonna

carry it away from the placenta it's

illustrated here in this red and you can

see the arrows and it's going to take it

away from the placenta because it's rich

in oxygen and nutrients and send it to

the baby now there are two umbilical

arteries and they carry deoxygenated

blood so blood that's really low in

oxygen so here it's represented in blue

we have the arrows going back to the

placenta so the baby has used up that

nice nutrients and oxygenated blood that

the mom sent it but now has waste in it

and it needs to get reoxygenate 'add so

it's going to leave via these two

umbilical arteries and send it back to

the placenta so now let me walk you

through fetal circulation of a baby who

is in utero and then follow that up with

how that fetal circulation changes once

they are born and they start breathing

on their own so we're gonna start here

about this placenta and specifically

we're gonna start at the umbilical vein

how many umbilical veins are there one

and what kind of blood does it carry

oxygenated so it has nutrients and

oxygen in it so it has pulled from Mom's

circulation that oxygen and nutrients

and it's gonna flow down through this

vessel and then it's going to hit the

liver

now the liver is not fully functional

yet but it does have some blood flow so

some of that blood is going to go

through the paddock portal vein the

majority of it is going to be shunted to

the inferior vena cava so this is our

first shot

the ductus venosus so the ductus venosus

is going to help shunt this rich

oxygenated nutrient-rich blood and it

wants to get it to the heart so it's

going to enter in to the inferior vena

cava now also and then fear your vena

cava just like over here with a normal

heart blood flow it's blood that's

draining back from the baby that is low

in oxygen that's a deoxygenated so this

blood is going to flow up and it's going

to enter into the right atrium just like

how it did over here now there's some

really cool things going on in this

right atrium first of all most of this

rich oxygenated blood is actually going

to flow over here to this left side via

a shunt which is our second shunt called

the foramen ovale so the frame in ovalle

is going to connect your right atrium to

your left atrium because remember what

did we say over here was the whole goal

of this right side to get deoxygenated

blood to the lungs but over here our

lungs aren't working so we need to take

this fresh blood with oxygen that we

just received from mom and we need to

get it to this left side because the

left sides want to get it to the body we

don't need it to go through this right

side and hit the lungs so majority of

this fresh rich rich oxygenated blood is

going to go and flow over here into the

left atrium it's going to go down into

the left ventricle up through the aorta

and replenish the body now another thing

that is occurring in this right atrium

is the flow of blood draining back to

the body that is deoxygenated so you

have the superior vena cava flowing in

this deoxygenated blood a majority of

this blood is actually going to go down

into this right ventricle because the

body needs to get this deoxygenated

blood back to this placenta and how it's

going to do this is it needs it to go

here on this side so the blood is going

to flow down here hit the right

ventricle now

also some of this rich oxygenated blood

that came from this umbilical vein is

also going to flow down in here as well

so the blood is going to be mixed with

oxygenated and deoxygenated blood and

it's going to be pumped up through the

pulmonary artery now normally this

pulmonary artery was sent it to the

lungs well it will sing a little bit to

the lungs just to maintain the lung

tissue but most of it is going to

actually be shunted away and this is

where our third son is this is the

ductus arteriosus so it's going to be

shunted from the pulmonary artery into

the aorta so that's what our ductus

arteriosus does it connects our

pulmonary artery to our aorta now you

may be wondering how is this able to

happen how are these structures able to

allow blood to be shunted here into

cross from right atrium to left atrium

well there's a pressure difference let

me go over this with you real fast in

these lungs that are non-functional the

resistance is really high because

there's fluid in there because it's

really high it's making the pressure in

this right side a lot higher than the

left side so because we have that

pressure difference this allows

oxygenated blood to easily flow through

this frame and ovalle and hit this left

side also it allows the blood to just

flow up through this ductus arteriosus

into the aorta because it's easier for

blood to flow from a higher resistance

to a lower resistance now keep that in

mind because after birth those pressures

are going to change and that is what

really affects our shunts and helps them

still close off so just keep that in

mind so majority of this mixed blood is

flowing down through this aorta

specifically the descending aorta now

some of that blood is going to go down

to the lower extremities and help those

out because it's mixed it has some

oxygen in it but this descending

Horta is when a branch off and it has

different branches and we have the

internal iliac artery which will connect

to our umbilical arteries and again what

do the umbilical arteries do there's two

of them it can they carry the

deoxygenated blood so we're going to

take that blood and we're gonna get it

back to mama who is going to remove that

waste and help replenish it so this

cycle will just keep going over and over

so now let's talk about how this changes

after birth so a baby is born and they

saw it breathing on their own what's one

of the first things they do after the

baby is born they cut the umbilical cord

so when we cut the umbilical cord we are

stopping this whole transfer of blood

flow back and forth so especially with

the umbilical vein we do not need the

ductus venosus so it disappears now

remember the resistance thing I was

talking about earlier with the lungs

so before baby's breathing on their own

and they have fluid in their lungs the

resistance is really high in here we're

just making the resistance on the right

side a lot higher than compared to the

left side of the heart but once baby

starts breathing they clear all that

fluid out of their lungs those sacs pop

open the resistance drops so whenever

that drops that's going to change the

pressure over here on the right side of

the heart it's actually going to become

a lot lower on the right side compared

to the left side so now we don't need

that shunting of the blood it's not

really gonna happen because we've

changed the pressure so this is going to

help the frame in ovalle close so you

won't have this connection anymore

between your right atrium and left

atrium because now we need blood to go

and do its job like how it does on the

right side we need to majority up

through this pulmonary artery and hit

those lungs now in some people this

framin ovalle doesn't close and we call

this a patent foramen ovale a PF oh and

I have a whole series on congenital

heart defects if you want to check out

that video that will talk about this

along with the patent ductus our

Yuriy osis so that closes then we have

the ductus arteriosus and this closes we

have the pressure changes you're not

going to have the high pressure here

pulmonary artery allowing it to flow up

here into the aorta but we've also

removed this placenta the placenta

produces prostaglandins and this vessel

is really sensitive to prostaglandin so

when we cut that out we decrease the

prostaglandins that's gonna help close

this ductus arteriosus plus the baby's

breathing on their own oxygen levels are

up and so we don't need that structure

anymore and it will still off okay so

that wraps up this review over fetal

circulation and don't forget to access

the free quiz that will test you on this

content