Foetal circulation and adaptation at birth

Question 1

how does blood from the foetal hart get to the placenta and back

Answer 1

umbilical arteries and umbilical vein

Question 2

What are the functions of the placenta

Answer 2

Homeostasis
Gas exchange
Nutrients
Hormone production
Transport of IgG

Question 3

placenta is … resistance path and lungs are … resistance path

Answer 3

low
high

Question 4

What is the role or special about the lungs, liver and gut in a foetus

Answer 4

Lung filled with fluid and unexpanded
Liver has little role
Gut not in use

Question 5

Where does oxygen, nutrient rich blood come from and which side of the heart does it reach

Answer 5

Placenta
Right side

Question 6

What does the ductus venous connect

Answer 6

Umbilical vein with the inferior vena cava

Question 7

What is the foramen oval and what path does it make possible

Answer 7

Opening in atrial septum connecting RA to LV
Allows oxygenated blood to enter LA then LV then ascending aorta and carotids - supply brain and heart

Question 8

how many % of the RV output goes to the lungs

Answer 8

7%

Question 9

Where does the rest of the RV output goes

Answer 9

Via ductus arterioles to join descending aorta

Question 10

What changes happen to the lungs at birth

Answer 10

Hormones are released in labour foetal lungs stop being producers of fluid and start being able to absorb fluid
Foetal takes big breath and cries which pushes fluid out the lungs and into lymphatic system where its drained

Question 11

what are the circulatory changes at birth

Answer 11

Pulmonary vascular resistance decreases
Systemic vascular resistance increases - cord clamped and cut
Means more of the cardiac output goes to the lungs

Question 12

How does the pulmonary vascular resistance decreases

Answer 12

When foetus breathes in, lung expands
Increase in circulating oxygen - vasodilator
PVR reaches normal adult - type level by 2-3 months

Question 13

What are the changes in the shunts at birth

Answer 13

Foramen oval closes
Ductus arterioles constricts

Question 14

How does the Foramen oval closes

Answer 14

As pulmonary vascular resistance falls and systemic vascular resistance rises left atrial pressure exceeds right atrial pressure and flap is pushed close

Question 15

How long does it take for the functional and anatomical closure of the ductus arterioles

Answer 15

Functional closure within hours to days
Anatomical closure within 7-10 days

Question 16

How is the Ductus arterioles closed

Answer 16

Oxygen tension increases causing vascular smooth muscle of duct to constrict
Less blood is flowing through the duct (more to lungs)
PGE2 levels are reduced - no longer connected to placenta and PGE2 is metabolised by lungs
Ends up as fibrous ligament - ligament arteriosum