Topic 8: Fetal Circulation Flashcards by Rachel ramella

In the fetus, organs that do not function until birth – (3)

Lungs
Kidneys
GI Tract

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Wastes and CO2 are eliminated via diffusion into the maternal blood
Exchange occurs via the placenta- what two ways?

Inside the uterus

Attached to baby via the umbilical cord

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Placenta - definition

–way of communication between mother and
baby
Site of exchange of nutrients/ wastes

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Umbilical Artery - def

–carries blood away from the fetus to the placenta
Carries wastes and CO2
LOW O2 Content!

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Umbilical Vein

–carries blood from the placenta to the fetus
Carries nutrients and O2
HIGH O2 Content

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Fetal Capillaries

–Umbilical arteries and veins branch into

these capillaries located inside the intervillous spaces in the placenta

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Intervillous Spaces

–Spaces filled with maternal blood from uterine arterioles. Drained by Uterine veins.

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The placenta communicates with the mother’s cardiovascular system via?

uterine blood vessels

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Nutrients travel from mother’s blood vessels to the intervillous space via ?

uterine arteries.

Diffuse from the intervillous spaces into the fetal capillaries

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The concentration of hemoglobin in fetal blood is about what % different than maternal blood??

50% higher

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Fetal hemoglobin has a greater affinity for oxygen than maternal blood – how much more oxygen can it carry?

Can carry 30-35% more oxygen

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Is there direct mixing of maternal and fetal blood?

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Exchange of gases–CO2, O2, CO

Accomplished via?

diffusion

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Exchange of gases–O2 – rate of extraction?

20-30mL O2/min extracted

Short interruption in blood flow can be fatal to fetus

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Exchange of gases–CO2, O2, CO

-Depends on rate of what?

Depends on delivery not rate of diffusion

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Exchange Nutrients/ Electrolytes - examples?

Amino Acids, Free Fatty Acids, Carbohydrates, Vitamins

Exchange is rapid and increases as pregnancy increases

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Exchange Nutrients/ Electrolytes -

Exchange is rapid and increases as what?

pregnancy increases

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Placental circulation resistance?

very low

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Transfer of Maternal Antibodies - starts when?

fetus makes components of what?

Late first trimester–fetus makes components of complement

Start of immunological competence

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What type of Immunoglobulins primarily?

at what week?

–Primarily IgG
Transported from mother to fetus (at about 14
weeks)
Provides passive immunity
Newborns produce own IgG, but don’t reach adult levels until about age 3

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Hormone Production in placents begins what month?

4th month

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Hormone Production
–placenta produces enough of what?
to support pregnancy, should corpus luteum fails

progesterone

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The placenta Continues to produce what kind of hormones?

Rises until end of pregnancy

estrogenic hormones

Estriol

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Blood passes from the fetus to the placenta via __ umbilical arteries
Branch of what??

2
internal iliac arteries

Sat ~58

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Oxygenated blood returns from the placenta via 1 umbilical vein -- what is the Oxy Sat %??

sat ~80%

umbilical vein -- Goes to the liver of the fetus where it divides into what 2 branches?

--Joins hepatic portal vein-> Liver (1/3) ---Ductus Venosus-> IVC (2/3) Sphincter mechanism in ductus that controls blood flow through the liver

In the IVC, oxygenated blood via what?? meets deoxygenated blood from the lower body Sat falls to about 67%

ductus venosus

Most fetal blood passes through what in the Heart?

``` Foramen Ovale (Hole between the Right and Left Atria) Blood entering from the IVC is guided toward the foramen ovale to the Left Atrium ``` (most does not go from the RV to the lungs)

In the LA, blood mixes with the very small amount of blood returning from the pulmonary veins and goes where?

to the LV

LV pumps the oxygenated blood into the aorta, this blood perfuses what two areas?

Perfuses the brain and myocardium | Getting highest O2 content available

Fetal blood returning to the heart from the SVC take what path through heart?

bypasses the Foramen Ovale and enters the RA | Goes to the RV and pumped to the PA

Pulmonary Vascular Resistance is so high that what happens to the blood supposed to go out the pulmonary arteries? what path does it take?

95% of this blood bypasses the pulmonary arteries Travels across the ductus arteriosus to the descending aorta Ductus arteriosus connects PA and Aorta

Pulmonary Vascular Resistance is ?

so HIGH

At the common iliac branch to the internal and external iliacs Part of that blood flowing systemically will flow through the internal iliacs to where? for what?

the internal iliacs to the umbilical artery | Will go to the placenta for nutrient/waste exchange

The only fetal vessel to carry fully oxygenated blood is what?

umbilical vein

Blood entering the aorta from the LV and perfusing the head and heart has higher ____ than the blood perfusing the rest of the body.

oxygen content

At birth, what systems start to function?

the Pulmonary, Renal and Digestive Systems

There are 3 shunts present in the fetal circulation that normally close after birth:

Ductus Arteriosus Foramen Ovale Ductus Venosus

Umbilical arteries functionally close when?

a few minutes after birth

Umbilical arteries will eventually fill with? (after birth)

connective tissue Distal portion will become fibrous cords Medial umbilical ligaments IN BABY

Umbilical arteries complete closure when?

2-3 months

Umbilical Vein Collapse when?

shortly after the umbilical arteries

Umbilical Vein remains as the?

ligamentum teres hepatis | - Lower margin of the falciform ligament. Attaches the umbilicus to the liver in baby!

Blood from the placenta may enter newborn for some time after birth via what?

Umbilical vein

What happens to the Ductus Venosus after birth?

Collapses Remains as Ligamentum Venosum Fibrous cord on the inferior surface of the liver

Occurance of a Patent Ductus Venosus?

extremely rare | Less than 20 reported world wide

Foramen Ovale - after birth? Anatomical (permanent) closure occurs within the first year of life

Usually closes after birth to become the Fossa Ovalis The first breath causes the lungs to expand and blood flow to the lungs increases. Blood returning to the LA increases its pressure, And pressure in the RA falls. First breath presses the septum primum against the septum secundum causes functional closure of the foramen ovale at birth. Constant apposition leads to fusion of the septa.

cyanotic periods of newborns caused by what?

The Foramen Ovale -- first days of life, closure is reversible Crying by baby creates a right to left shunt and can account for the cyanotic periods of newborns.

When does permanent (anatomical) closure of the septa occure?

within the 1st year of life

After a year, if the Foramen Ovale has not closed, it is referred to as what? prevalence of this happeninf?

a Patent Foramen Ovale (PFO). 27% prevalence of PFO Most patients are a symptomatic

Umbilical Arteries becomes after birth?

Medial Umbilical Ligaments

Ductus Arteriosus becomes after birth?

Ligamentum Arteriosum

Umbilical Vein becomes after birth?

Ligamentum Teres (Round Ligament)

Ductus Venosus becomes after birth?

Ligamentum Venosum

Foramen Ovale becomes after birth?

Fossa Ovalis

Ductus Arteriosus Closes via what ?

contraction of the muscular wall immediately after birth. Mediated by Bradykinin which is released by the lungs during the initial inflation. After the first breath, the lungs fill with air instead of fluid Pulmonary vascular resistance falls Pulmonary blood flow increases

Ductus Arteriosus Closure mediated by?

Mediated by Bradykinin which is released by the lungs during the initial inflation.

Ductus initially protects the pulmonary vasculature from what?

overload

Ductus Arteriosus Closure time in a full term infant?

Takes about 1-2 days to close in a full term infant

Ductus Arteriosus complete obliteration of the lumen takes?

1-3 months