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24- Blood and blood vessels > Vascular changes at parturition > Flashcards

Vascular changes at parturition Flashcards

1
Q

Why is fetal circulation different

A
  • Fetus ‘breaths’ amniotic fluid
  • Fetal blood is oxygen-poor
  • Fetus swims in amniotic fluid
  • Fetus is fed via umbilical cord
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2
Q

What is the significance of the fetus breathing amniotic fluid

A

The pulmonary artery doesn’t carry oxygen

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3
Q

What is the significance of the fetus being fed primarily through the umbilical cord

A

The hepatic portal vein is not needed

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4
Q

What functions in the neonate does the placenta replace

A

Performs gas exchange as lungs are collapsed, Removes waste instead of the kidneys and liver,
Stores fuel instead of the fat/muscles/liver

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5
Q

What is a fetal shunt

A

A passage or anastomosis between two natural channels such as blood vessels

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6
Q

What are the 3 key shunts of fetal circulation

A
  • Ductus venosus
  • Foramen ovale
  • Ductus arteriosus
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7
Q

What is the urachus

A

fibrous remnant of the allantois, a canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord

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8
Q

What is the role of umbilical arteries

A

Pick up nutrients from the placenta

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9
Q

Where is the ductus venosus located

A

between the umbilical vein and the vena cava. Backside of liver

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10
Q

What does the ductus venosus do

A

connects the umbilical vein to the inferior vena cava

  • Allows 50% of the blood to bypass the liver
  • Streams blood to foramen ovale
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11
Q

Where is the foramen ovale located

A

Within the interatrial septum

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12
Q

What is the function of the foramen ovale

A

the foramen ovale diverts blood away from the pulmonary arteries and into the left atrium
- shunts oxygenated blood straight through right atrium to left atrium

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13
Q

What is the significance of foetal blood being shunted through foramen ovale?

A

Blood goes from RA to LA, then into the LV and the aorta. Meaning that oxygenated blood leaves from both the pulmonary trunk and aorta and goes straight up from heart to brain and back to heart.

Does not go to lungs is the main reason

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14
Q

What is the ductus arteriosus

A

a vessel in a growing fetus has that connects the pulmonary artery with the aorta, instead of going to the lungs the blood goes to the body

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15
Q

What is the effect of the pressure differential in the ductus arteriosus

A

Pressure differential between lungs and lower body streams flow back to placenta

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16
Q

What happens after the umbilical cord is ligated and the placenta detaches

A

There is no blood in the umbilical vein- this means the ductus venosus sphincter constricts

17
Q

What happens to the blood flow after the ductus venosus sphinter constricts

A

blood is diverted through the liver (hepatic portal vein)

18
Q

What is PGE2 responsible for

A

It is a vasodilator that disappears at birth, allowing the shunts to naturally constrict

19
Q

What happens during the closure of the foramen ovale

A
  • Lungs open, meaning low pulmonary resistance
  • Placenta is now gone, meaning high systematic pressure
  • Pressure differential causes the septa to close and fuse, blood now travels to the lungs via right ventricle
20
Q

What happens to the ductus arteriosus after birth

A

pO2 increases, PGE2 decreases, leading to constriction of the ductus arteriosus

21
Q

What is the effect of the ductus arteriosus constricting

A

Blood flow can go to the lungs, lower pressure in the lungs also helps promote blood flow to the area

22
Q

What is the time span for ductus venosus closure

A

Functional closure in minutes

Anatomical closure in days

23
Q

What is the time span for closure of foramen ovale

A

Functionally= hours
Anatomically= weeks or years
The foramen ovale can persist throughout life in some animals

24
Q

What is the time span for closure of ductus arteriosus

A 
Functionally= minutes to hours
anatomically= 2-7 days
25
Q

What happens in the event of the failure of the ductus arteriosus to close

A

This results in a ventricular septal defect, which can reduce the efficiency of the heart

26
Q

What is the fate of the umbilical arteries after birth

A

become round ligaments of the bladder

27
Q

What is the fate of the umbilical vein after birth

A

become round ligaments of the bladder

28
Q

What is the fate of the ductus venosus after birth

A

becomes ligamentum venosum

29
Q

What is the fate of the foramen ovale after birth

A

becomes fossa ovalis

30
Q

What is the fate of the ductus areteriosus after birth

A

becomes ligamentum arteriosum

24- Blood and blood vessels (9 decks)

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