anatomy (foetal circulation)

8/7/2019 ANATOMY (foetal circulation)

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ANATOMY

Dr. Dakubu


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FOETAL CIRCULATION

During pregnancy, the fetal circulatory system

works differently than after birth:

The fetus is connected by the umbilical cord to

the placenta, the organ that develops and

implants in the mother's uterus during

pregnancy.


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Through the blood vessels in the umbilical

cord, the fetus receives all the necessary

nutrition, oxygen, and life support from the

mother through the placenta.

Waste products and carbon dioxide from the

fetus are sent back through the umbilical cord

and placenta to the mother's circulation to be

eliminated.


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Blood from the mother enters the placentaand comes in close proximity to the fetal

blood that has returned from the fetus to the

placenta through the umbilical arteries.

Once the two circulations are in close

proximity in the placenta, the oxygen (O2) and

nutrients, like sugar, protein and fat molecules

can move from maternal to fetal blood, andcarbon dioxide (CO2) and waste products can

move from fetal to maternal blood.


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The maternal blood returns from the placenta

to the mother's veins for her systems to take

care of the waste


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The new well nourished fetal blood returns tothe baby through the umbilical vein.

The umbilical vein goes to the liver and splitsin to three branches, one of which connects tothe inferior vena cava, a major vein connectedto the heart.

In this way the well nourished blood reachesthe fetal heart to be sent to the rest of thebody.


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Inside the foetal heart:

Blood enters the right atrium, the chamber on

the upper right side of the heart.

Most of the blood flows to the left sidethrough a special fetal opening between the

left and right atria, called the foramen ovale.

Blood then passes into the left ventricle (lower

chamber of the heart) and then to the aorta,

(the large artery coming from the heart).


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From the aorta, blood is sent to the head and

upper extremities.

After circulating there, the blood returns to the

right atrium of the heart through the superior

vena cava.

About one-third of the blood entering the right

atrium does not flow through the foramen ovale,but, instead, stays in the right side of the heart,

eventually flowing into the pulmonary artery.


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Because the placenta does the work of exchangingoxygen (O2) and carbon dioxide (CO2) through themother's circulation, the fetal lungs are not used forbreathing.

Instead of blood flowing to the lungs to pick up oxygenand then flowing to the rest of the body, the fetalcirculation shunts (bypasses) most of the blood awayfrom the lungs.

In the fetus, blood is shunted from the pulmonaryartery to the aorta through a connecting blood vesselcalled the ductus arteriosus.


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With clamping of the cord, the detachment fromthe placenta and the first breaths of air the babytakes at birth, the fetal circulation changes.

By removing the placenta reservoir, the baby'svenous resistance/blood pressure goes up.

By filling the lungs with air, the blood pressure inthe lung arteries goes down.

This eventually leads to the closing of the twoareas for shunting, the patent foramen ovale(PFO) and the patent ductus arteriosus (PDA).


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Because the ductus arteriosus (the normalconnection between the aorta and thepulmonary artery) is no longer needed, it

begins to constrict and close off. The circulation in the lungs increases and

more blood flows into the left atrium of theheart. This increased pressure causes theforamen ovale to close and blood circulatesnormally.

anatomy (foetal circulation)

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