Fetal Circulation Flashcards

1
Q

4 shunts in fetal circulation

A
  1. Ductus venosus
  2. Foramen ovale
  3. Ductus arteriosus
  4. Umbilical arteries/Placenta
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2
Q

Ductus venosus

A

-Route for oxygenated blood from placenta to bypass the liver and enter the IVC

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3
Q

Foramen ovale

A

-Allows blood from IVC to pass from R to L atrium

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4
Q

Ductus arteriosus

A

-Blood from right ventricle goes through the ductus arteriosus to flow into the descending aorta and bypass the lungs

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5
Q

Umbilical arteries

A

-Blood in the descending aorta passes through hypogastric arteries into the umbilical arteries and then to the placenta

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6
Q

How saturated is blood in the umbilical vein?

A
  • Coming from placenta

- 85% saturated

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7
Q

How saturated is blood in the umbilical arteries

A
  • Going to the placenta

- 60% saturated

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8
Q

What triggers the first breath in a baby?

A
  • Mild hypoxia (still being researched)
  • Hypercapnia (still being researched)
  • Tactile stimuli
  • Cold skin
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9
Q

What accompanies the transition from fetal to neonatal circulation?

A
  • Dramatic drop in pulmonary vascular resistance

- Thus, blood flow increases and pulmonary arterial pressure decreases

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10
Q

What adult organ functions does the placenta perform?

A
  • Lungs: gas exchange
  • GI tract: nutrition
  • Liver: nutrition and waste removal
  • Kidneys: fluid and electrolyte balance, waste removal
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11
Q

What does placental insufficiency lead to?

A

-Type II intrauterine growth restriction (IUGR)

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12
Q

Fetal asphyxia

A

-Any insult that interferes with gas exchange causes it

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13
Q

Why is oxygen saturation higher for the fetus than for the mother?

A

-Because of the gamma chains in hemoglobin

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14
Q

Hb content of fetuses

A

-More than 50% higher than in the mother

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15
Q

Consequences of closing placental circulation

A
  • Peripheral resistance doubles

- Increase in aortic and left ventricle pressure

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16
Q

Closure of the foramen ovale

A
  • Increased pulmonary circulation causes increased venous return to L atrium
  • There is a decrease in R atrial pressure
  • This reversal of pressure causes the closure
17
Q

Closure of ductus venosus

A
  • Constriction of vascular smooth muscle–becomes ligamentum venosum
  • Mechanism is possibly increased PO2 and reduced prostaglandins
  • Failure of closure: portosystemic shunt
18
Q

Closure of ductus arteriosus

A
  • Constriction of the wall
  • Increased PO2 and decreased circulating prostaglandin, bradykinin
  • Failure of closure: patent ductus arteriosus can lead to pulmonary hypertension, CHF, and arrythmias