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MABS Physiology > Fetal and Neonatal Circulation > Flashcards

Fetal and Neonatal Circulation Flashcards

1
Q

In fetal circulation, when does the heart begin to develop?

A

by 3rd week, development of the heart begins

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2
Q

In fetal circulation, when does the atria form?

A

by 5th week, the atria are formed

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3
Q

in fetal circulation, when do the ventricles form?

A

by 5th week, the ventricles form

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4
Q

when does fetal circulation develop?

A

3rd week, embryonic blood vessels develop

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5
Q

when does the first heart beat happen?what is the heart rate? and prior to delivery?

A

4th week; 65 beats/min; 140 beats/min

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6
Q

what is the fetal circulatory system adapted to maximize?

A

gas and nutrient exchange between the mother

and the fetus

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7
Q

what is the fetal circulatory system adapted to provide?

A

a higher supply of oxygen to the developing organs with

high metabolic demand by bypassing the organs with low metabolic demand

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8
Q

what organs of the fetus require high demand of the fetal circulatory system?

A

heart, brain, upper body

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9
Q

what organs of the fetus require low demand of the fetal circulatory system?

A

liver, lungs, lower body

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10
Q

what is the fluid dynamics law?

A

Any fluid/gas will move from the area of higher pressure to the area of low pressure (including blood)

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11
Q

compare and contrast adult circulation with fetal circulation?

A

Adult circulation:
High pressure: Systemic circulation (left heart)
Low Pressure: Pulmonary circulation (right heart)

Fetal Circulation:
High Pressure: Pulmonary Circulation 
(collapsed lungs, constricted vascular tree)
Low Pressure: Systemic Circulation
(aorta and placenta)
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12
Q

what is the function of the shunt?

A

used inorder to maximize the perfusion of the organs with the high metabolic rate because babies lungs are collapsed and so blood comes from the mother

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13
Q

what are the four shunts in order?

A

placenta, ductus venosus, foramen ovale, ductus arteriosus

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14
Q

what is the placenta?

A

the first shunt used for fetal circulation and is a low resistance organ. It replaces the four separate organs: the lungs, GI system, Liver, and Kidneys

Gas exchange
nutriton and fluid regulation
nutrition and waste removal
fluid excretion and ion regulation

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15
Q

what percentage of blood does the fetal heart pump through the placenta?

A

40%

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16
Q

this shunt receives most of the combined cardiac output (CCO)?

A

the placenta

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17
Q

Blood flow from the mother to the placenta via?

A

Uterine arteries

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18
Q

Blood flow from the placenta to the mother via?

A

Uterine veins

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19
Q

Blood flow from the fetus to placenta via?

A

Umbilical arteries (two)
(deoxygenated blood, venous)
Capillaries
Villi

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20
Q

Blood flow from the placenta to the fetus via?

A 
Umbilical Vein (one)
(oxygenated blood, arterial)
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21
Q

what is the function of the umbilical arteries?

A

carry deoxygenated blood away from the fetus

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22
Q

what is the function of the umbilical veins?

A

carries oxygenated blood towards the fetus

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23
Q

what is the second shunt?

A

ductus venosus

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24
Q

what is the function of the second shunt?

A

shunts a portion of the left umbilical vein blood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.

25
Q

what is the ductus venosus regulated by?

A

the sphincter

26
Q

what percentage of CCO (combined cardiac output) passes through the ductus venosus?

A

50%

27
Q

what is the third shunt?

A

foramen ovale

28
Q

where is the third shunt located?

A

The oval hole in the septum which divides the right and the left atria (posterior wall of the right atrium)

29
Q

what percentage of the CCO shunts through the foramen ovale?

A

27%

30
Q

once the blood shunts from the right atrium to the left atrium what happens to the baby’s heart?

A

the baby’s heart can function normally

Supplied with increased O2 blood (IVC)
Receives some decreased O2 blood from the upper body (SVC)

31
Q

in terms of the shunt (foramen ovale) moving from right to left, what happens to the decreased oxygen from the SVC?

A

sent to the right ventricle (through the tricuspid valve) and towards the lungs

32
Q

what is the fourth shunt?

A

ductus arteriosus

33
Q

what is the function of the fourth shunt? because of this shunt, how are collapsed lungs affected, the aorta?

A

Diverts the blood from the pulmonary artery in to the aorta to systemic circulation and out via umbilical arteries, this is viewed as a right to left shunt because blood is pushed by mom so higher pressure

HIGHER PRESSURE ON RIGHT SIDE IN DEVELOPING FETUS

Collapsed lungs- increasedresistance
Aorta- decreased resistance (placenta)

34
Q

what leaves before the ductus arteriosus happens?

A

carotid arteries

35
Q

what is the composition of the Fetal HB? why is this important to note? what is the Hb concentration? is cardiac output high?

A

2 alpha and 2 gamma; it can carry 20-30% more O2 than the adult HB because the chains of the fetal hemoglobin have higher affinity for the oxygen than its adult form which is comprised of 2 alpha and 2 beta, shifts the curve to the left

the Hb concentration is high (Hit 40-60%)

the cardiac output is high too

36
Q

after birth, what causes our first breath?

A

physical stress during birth

sudden exposure to external temperature

post-birth hypoxia and hypercapnia

37
Q

what are the mechanisms that trigger the shift from the fetal to the adult circulation?

A

newborn breathing and removal of the placenta

38
Q

what is the effect of newborn breathing?

A

decrease pulmonary resistance

39
Q

what is the effect of the removal of the placenta?

A

increase systemic vascular resistance, the placenta must be removed

40
Q

what happens to the aortic pressure (systemic) after the removal of the placenta?

A

there is a sudden increase in the aortic pressure and pulmonary vascular resistance drops.

41
Q

after delivery, we know that the pulmonary system is affected, what is the effect of the first breath?

A

it leads to the expansion of the lungs (powerful)

42
Q

after delivery, we know that the pulmonary system is affected, is there an increase or decrease in pulmonary arterial pressure? right ventricular and atrial pressure? what can this drop in pressure be attributed too?

A

increase; increase, increase; O2 induced vasodilation

43
Q

during fetal circulation, pressure flows from which atria? what about after delivery, what happens to the pressure in each of the atria?

A

right to left; the foramen ovale closes and a high pressure system is created in the left atrium and a low pressure system is created in right atrium

44
Q

what happens when surfactant is not properly made and the ductus arteriosus does not close properly?

A

lungs will not function properly and atelectasis can develop

45
Q

what is the effect of ductus arteriosus closure?

A
  • cessation of blood flow due to closing of the umbilical vein
  • blood backs up from the portal vein
  • DV smooth muscle contracts
  • increase in portal vein pressure-perfusion to the liver
46
Q

what is the most important step after the delivery of the baby?

A

the closure of the ductus arteriosus (last to close) because if it stays open and they have a cardiac abnormality this has to be open otherwise the baby will die and this is done through a decrease in pulmonary pressure and increase in systemic pressure and can be maintained by the prostaglandins (keeps it open)

47
Q

what drug can we give to close the Ductus arteriosus?

A

indomethacin

48
Q

what is Patent Ductus Arteriosus (PDA)?

A

a left to right shunt develops and so failure of ductus arteriosus to close occurs and so their is an increase in aortic pressure leading to increase in blood flow through the PDA in to the pulmonary circulation thus increasing the pulmonary pressure

49
Q

what are congenital anomalies? examples?

A

malformations that occur during the embryonic development

Stenosis

Anomaly that causes a blood to flow from the left heart (systemic) to the right heart (pulmonary circulation)

Anomaly that causes blood to flow from the right heart (pulmonary) to the left heart (systemic circulation)

50
Q

what type of shunt is PDA?

A

a left to right shunt

51
Q

what type of shunt is Tetralogy of Fallout?

A

A Right to Left Shunt

Blue Baby

52
Q

what are the anomalies of Tetralogy of Fallout?

A

Aorta-originates from the right ventricle riding on the septum

Stenosis of pulmonary artery (bypass lungs)

Blood from the Right ventricle passes trough the septal defect
/the overriding aorta

Right ventricle enlargement

53
Q

what is the major problem with Tetralogy of Fallout (ToF)?

A

shunting of the blood from the pulmonary system → the systemic circulation

54
Q

what percentage of blood bypasses the lungs in ToF?

A

75 % of the blood bypasses the lungs with PDA saving the babies life

55
Q

what are the signs of ToF?

A

cyanotic baby with increased right ventricle systolic pressure and so we see the enlargement of the right ventricle

56
Q

treatment for ToF?

A

Surgical: Dilate the pulmonary stenosis, Close the septal defect, Reconstruct the aorta

57
Q

what is the life expectancy of ToF?

A 
2-3 (without the surgery) 
50 years (after the surgery)
58
Q

The cause of congenital heart defects before vaccinations was commonly caused by? secondary cause?

A

german measles; genetics: Some populations more prone for defects

MABS Physiology (57 decks)

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