Maternal And Fetal Circulation Flashcards by Lauren F

What are the 2 circulations in the placenta?

Uterus-placenta circulation
Placental-umbilical circulation

(They do not mix. Moms blood and baby’s blood stay separate)

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Are all of these functions of the placenta?

act as a lung to allow gas exchange
act as a kidney to remove waste
act as a GI tract to absorb nutrients
act as a barrier to protect the fetus from the moms immune system
act as an endocrine organ, producing steroids and growth factors

Yes

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How does maternal blood enter the intervillous space?

Via spiral arteries

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How does maternal blood leave the intervillous space?

Venous orifices

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How many umbilical arteries and veins are there

2 arteries

1 vein

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When fetal blood enters the chorionic villi through the umbilical arteries, is it oxygenated or deoxygenated?

It is DEOXYGENATED

deoxygneated blood in an artery get used to it!!!!*

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What are chorionic villi?

They are like alveoli in the placenta where the fetal blood is coiled up inside them and the maternal blood is around it and gas exchange takes place

(I think)

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Which has a higher PO2: the uterine artery or the umbilical artery?

Uterine artery (MOM’s artery is full of oxygen) PO2=100

Baby’s umbilical artery is DEoxygenated is is only 23

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What two changes happen during pregnancy that allow for fetal perfusion?

Maternal blood volume increases by 40%

Peripheral vascular resistance decreases

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What 2 changes happen in pregnancy that decrease the work of the moms heart?

Blood viscosity decreases

MAP decreases

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Mom’s blood volume increases 40% during pregnancy And she adds RBCs, but what happens to her hematocrit?

Hematocrit decreases by 2-3% because the plasma volume increases by 40-50%, but the RBCs increase only by 30%

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Why would we want more maternal blood volume in a pregnant woman

Protects against impaired venous return when standing up

Ameliorates blood loss during birth

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What happens to CO during pregnancy? Why?

CO increases 30-50%

HR and SV increase

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What happens to ventricular volumes in pregnancy

They increase, which promotes frank-starling mechanism of increased CO

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What parts of the body get more blood flow during pregnancy?

Kidneys (a lot more)

Uterus

Heart

Skin

Breasts

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Which parts of the body do not get increased perfusion during pregnancy?

Brain

Gut

Skeleton

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What causes decreased peripheral resistance in a pregnant woman

Addition of the low-resistance placental circuit

Estrogen and other factors

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Does the MAP stay low throughout the entire pregnancy?

No, during mid-pregnancy, it returns to its original level

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What is the effect of adding a placenta on resistance?

Decreases resistance

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What kinds of chemical signaling does placenta cause?

Placental and maternal steroid increase

Prostaglandin increases

Increased angiotensin II and aldosterone (mother has decreased sensitivity to angiotensin II)

Increased NO production via eNOS expression in placental endothelium

(**these chemical signals target the fetus and/or the mom)

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Why is it important that the mom has a decreased sensitivity to the angiotensin II released by the placenta?

We want her BP to stay low

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What kinds of cardiovascular remodeling occurs during pregnancy?

LV gets thicker

Valve orifice areas increase

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Do non pregnant women have spiral arteries?

Yes

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What happens to the spiral arteries in a pregnant uterus?

It gets remodeled to have a larger diameter and a much lower pressure

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What is preeclampsia?

Elevated maternal BP | Either 140+ systolic or 90+ diastolic

What are the 2 stages of preeclampsia?

1. Altered perfusion causes placental ischemia | 2. Ischemic placenta freaks out and releases factors that cause the mom to vasoconstrict and develop HTN

What kinds of things can cause the placenta to become ischemic?

- placenta is abnormally shaped or has weird vasculature - spiral artery remodeling gone wrong - placental abruption

Does the fetal heart work in parallels or series?

Parallel*** | Different than in adults

What are the 4 fetal structures related to fetal blood flow?

1. Placenta 2. Ductus venosus 3. Foramen ovale 4. Ductus arteriosus

Is the fetal pulmonary circuit low flow and high resistance? Or is it high flow and low resistance?

It is low flow and high resistance | Opposite of adults

What is the Combined cardiac output when were talking about the fetal heart?

The blood pumped from the left heart and the right heart

How much of the combined cardiac output does the placenta receive from the fetus’s heart

50%

What kind of blood is carried in the umbilical vein to the fetus?

High O2 saturated blood

What kind of blood is carried by the umbilical artery away from the baby and to the placenta?

Mixed blood ***** | Purple

Which of the baby’s organs get blood shunted away from them?

Abdominal viscera Lower body

What does the ductus venosus do?

It shunts blood from the umbilical vein (RED BLOOD) to the IVC, bypassing the liver. Blood from the IVC and the portal vein combine with the umbilical blood (makes it purple)

What does the foramen ovale do?

It shunts blood from the RA to the LA after it is shot into the RA by the Inferior vena cava

Which vena cava supplied well oxygenated blood to the Right atrium?

The IVC only! Superior vena cava delivers blue blood

Which ventricle gets more of the CCO?

The right ventricle **** 66% vs 34% in the LV

What percentage of the CCO comes into the RA from the IVC?

69% | Hee hee

Along the aortic arch, the ductus arteriosus is AFTER the branching of the blood supply to the brain and upper body. What effect does this have?

Well oxygenated blood gets delivered to the brain Mixed blood gets delivered to the descending aorta and therefore the placenta and lower body

Which ventricle in the fetus has blood that is better oxygenated?

The Left ventricle. It is 65% oxygen | The right ventricle is not oxygen “poor,” it is mixed blood that is 55% O2

What parts receive blood flow from the right heart in a fetus?

Left heart (via Foramne Ovale) Body (via Ductus arteriosus) Lungs (via pulmonary artery, but only about 7%)

What parts receive blood flow from the left heart?

The body and the placenta

Where is the blood coming into the R atrium coming from?

IVC that is is mixed blood from the placenta and the portal vein SVC that is oxygen poor from the body

The placenta is a ___ resistance, ____volume vascular bed that receives ___% of CCO

Low resistance High volume 50% of CCO ***********

The R&L hearts are in (parallel/series) because the inputs and outputs mix and both deliver blood to the body*****

Parallel | *******

The CCO from both fetal ventricles is ______% The RV provides ____% The LV provides _____%

100% RV- 66% LV- 34%

Cardiac and vascular shunts allow for a large volume of oxygenated blood to get to the ______ circuit while bypassing the ______ circuit

Systemic Pulmonary

What happens to the total peripheral resistance of the baby when you cut the umbilical cord?

It doubles the total peripheral resistance (loss of a vascular bed)

What happens to aortic and left atrial pressure right after the baby is born?

Increase

When the baby takes its first breath and the lungs expand, what happens to pulmonary vascular resistance?

It drops by a lot bevcause you are suddenly having increased amount of vasculature opening up

What happens to the pulmonary arterial pressure when the lungs expand?

It drops, because the blood flow can now go into all these newly opened vessels

In utero, the fetal heart is a medium-pressure system on both sides, what causes it to become a low pressure pump on the right and a high pressure pump on the left?

- pulmonary vasculature opens up causing the right side to be low pressure - more blood is returned to the left atrium causing an increase in left side pressure

What causes the foramen ovale to close right away?

The pressure in the left atrium becomes HIGHER than the pressure in the right atrium, and that causes it to close up ******** ~~pressure differential ~~

What keeps the ductus arteriosus open during pregnancy

Prostaglandins from the placenta

What are the two reasons the ductus arteriosus closes?

1. Loss of prostaglandins from the placenta 2. Pressure in the aorta is now higher than the pressure in the pulmonary artery, causing blood flow to reverse**. The increased O2 in the aorta triggers a smooth muscle response that closes it * *************************

After birth, what happens to the CCO between the LV and RV?

It becomes 50/50

3-18 days after birth, the increased oxygen levels cause the ductus venosus to close, what is the result of this?

Functioning liver! Portal vein blood goes into the liver instead of the IVC

What happens to the thickness of the RV and the LV after birth?

RV gets thinner LV gets thicker due to increased peripheral resistance

What are the results of an atrial septal defect?

L —> R shunt causes: Oxygenated blood into R atrium Blood in RV is at 90% oxygenation (normal 75%) More blood to lungs Right atrium dilates Pulmonary vessels dilate Pulmonary hypertension develops

What are the results of a ventricular septal defect?

L—> R shunt in ventricles causes: R side of heart gets overloaded Pulmonary HTN develops Increased pulmonary return to the L atrium RV sends more blood to lungs

What happens if the ductus arteriosus remains open?

L —> R shunt**** (aorta squirts into pulmonary artery) Increase in pulmonary and RV pressure L heart becomes overloaded due to increased pulmonary return Systemic blood remains normally oxygenated****

Maternal And Fetal Circulation Flashcards

(63 cards)