The foetal circulation and adaption at Birth Flashcards Preview

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Flashcards in The foetal circulation and adaption at Birth Deck (38)
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1

Function of placenta?

Fetal homeostasis
Gas exchange
Acid base balance
Nutrient transport to fetus
Waste product transport from fetus
Hormone production
Transport of IgG
Prostaglandin E2

2

How fetal circulation differs from adult circulation? (4)

-Placenta is included in fetus fro - gas exchange, nutrition, waste excretion and homeostasis
-Lungs are fluid filled and unexpanded
-Liver has little role in nutrition and waste management
-Gut is not in use

3

What do the umbilical arteries do?

Take deoxygenated blood to placenta

4

What does umbilical vein do?

Take oxygenated blood from the placenta back to foetus

5

Where does the placenta sit?

End of the umbilical cord

6

What are the 3 shunts specific to foetal life?

Ductus venosus
Foramen Ovale
Ductus arteriosus

7

Where does blood go when returning from the placenta?

Right side of the heart- then distributed to growing foetus

8

Anatomy of the ductus venosus?

Connects the umbilical vein to the inferior vena cava

9

Anatomy of the foreman ovale?

Opening in the atrial septum connecting RA to LA

10

Anatomy of ductus arteriosus?

Connects pulmonary bifurcation to descending aorta

11

What does the ductus venous do?

Carries majority of blood from the placenta into the inferior vena cava bypassing portal circulation (liver)

12

What does the ductus venous do?

Carries majority of blood from the placenta into the inferior vena cava bypassing portal circulation (liver)

13

Function of the foreman ovale?

Allows blood to flow from RA to LA
Allows best oxygenated blood to enter LA then go into LV, to ascending aorta and then carotids

14

What is the foreman ovale physically?

Membrane flap on left atrium side

15

How is the ductus arteriosus kept open?

Circulating prostaglandin E2 produced by the placenta

16

How much of the RV output in a fetus goes to the lungs?

7%

17

Where does majority of the RV output go in a fetus?

Ductus arteriosus to join the descending aorta

18

What happens to a baby in the few minutes following birth?

Baby inflates lung and cries
Goes from blue to pink
Cord is clamped and cut

19

Changes in pulmonary vascular resistance when a baby is born?

Decreases
Breath in- lungs can physically expand
Increased circulating oxygen

20

Changes in systemic vascular resistance when a baby is born?

Increases
Cord clamped and cut

21

General circulation changes when a baby is born?

More of cardiac output goes to lungs

22

How does the foreman ovale close?

As PVR falls and SVR rises- the left atriall pressure exceeds the right atrial pressure
-Flap is pushed closed
-Once the cord has been clamped the pressure in the left side becomes higher than the pressure in the right

23

Explain duct constriction?

Decreased PVR cause a decrease in flow
Decreased circulating PGE2 due to increased lung metabolism
Increased PO2= oxygen sensitive muscular layer
Shunt becomes bidirectional than left to right
Physiologically it closes withing first 24 hours, anatomically closes withing 7-10 days

24

In what types of patients is a patent ductus arteriosus common?

Preterm infants

25

Treatment options for failure of duct closure?

Wait and see
Surgery
NSAIDS (Nonsteroidal anti-inflammatory drugs)

26

What can be used to keep a duct open?

PGE2
Prostaglandin E2
Until an alternative shunt is established or a definitive surgery carried out

27

Duct dependent circulation?

Some congenital heart diseases cause this where the duct must be kept open with PGE2

28

What happens to pulmonary resistance when a baby is born?

Continues to drop until it reaches adult level about 2-3 months later

29

When is persistent pulmonary hypertension of the newborn more likely?

Sick babies-
Sepsis
Hypoxic ischaemic insult
Meconium aspiration syndrome
Cold stress

Can be related to underlying anatomical abnormality = congenital diaphragmatic hernia

30

When does PPHN occur?

Lung vascular resistance fails to fall after birth