Foetal circulation and adaptation at birth

Question 1

Which functions is the placenta included in?

Answer 1

Foetal circulation
Gas exchange
Nutrition
Waste excretion
Homeostasis

Question 2

Via which artery does blood travel from the foetal heart to the placenta?

Answer 2

The umbilical arteries

Question 3

Via which vein does blood travel from the placenta to the foetus?

Answer 3

The umbilical vein

Question 4

What are the 3 shunts of the foetal circulatory system?

Answer 4

Ductus venosus
Foramen ovale
Ductus arteriosus

Question 5

What is the function of the ductus venosus?

Answer 5

It connects the umbilical vein to the inferior vena cava, bypassing the hepatic system and liver

Question 6

What is the function of the foramen ovale?

Answer 6

The foramen oval is an opening between the left and right atria and allows passage of the blood between them. This is because there is no pulmonary circulation so oxygenated blood from the mother passes into the aorta

Question 7

What is the function of the ductus arteriosus?

Answer 7

It connects the pulmonary artery to the aorta, allowing some of the blood that passes into the right ventricle to return to the aorta

Question 8

What keeps the ductus arteriosus open?

Answer 8

Prostaglandin E2

Question 9

Where is prostaglandin E2 produced?

Answer 9

In the placenta

Question 10

How is blood directed through the foramen ovale?

Answer 10

The musculi pectinati (Pectinate muscles) in the auricle of the right ventricle direct blood into the foramen ovale

Question 11

What is the average saturation rate of a foetus?

Answer 11

~70%

Question 12

What are the 2 major adaptations to circulation after birth?

Answer 12

Cutting of the umbilical cord increases SVR
First breaths and crying introduces oxygen, which is a potent vasodilator, which decreases pulmonary vascular resistance

Question 13

What causes the closure of the foramen ovale?

Answer 13

As SVR increases and pulmonary VR decreases, pressure in the left atrium increases more than that of the right atrium, which causes the closure of the flap on the left atrium side

Question 14

What causes closure of the ductus arteriosus?

Answer 14

Decrease in prostaglandin levels
Decreased flow due to pressure differences
Oxygen levels rise, reacting with the oxygen sensitivity muscular layer in the ductus arteriosus

Question 15

What does closure of the ductus arteriosus form?

Answer 15

The ligament arteriosum

Question 16

What condition occurs when the ductus arteriosus does not close?

Answer 16

Patent ductus arteriosus

Question 17

What is the treatment for patent ductus arteriosus?

Answer 17

NSAIDs such as ibuprofen which interrupts prostaglandin levels, which allows closure of the ductus arteriosus
Catheters or clips can also be used to manually close it

Question 18

What is meant by interruption of the aortic arch?

Answer 18

The aortic arch is closed off at one point and the descending aorta is only fed by the ductus arteriosus

Question 19

What is the main treatment for interruption of the aortic arch?

Answer 19

IV prostaglandin E2 and then surgery with a stent

Question 20

What are some conditions that can increase likely hood of persistent pulmonary hypertension of the newborn?

Answer 20

Sepsis
Hypoxic ischaemic insult
Meconium aspiration syndrome
Cold stress

Question 21

What is the cause of persistent pulmonary hypertension of the newborn?

Answer 21

The pulmonary vascular resistance doesn’t decrease and stays high, meaning lung pressure is greater than SVR