2: Foetal circulation and adaptation at birth

Question 1

The ___ is responsible for fetal ___.

Answer 1

placenta , homeostasis

Question 2

What maintains the patency of the ductus arteriosus when a baby is in utero?

Answer 2

Prostaglandin E2

Question 3

What is the site of gas exchange, nutrition, waste excretion and homeostasis in a foetus?

Answer 3

Placenta

Question 4

In a foetus, the lungs are ___-filled and ___.

Answer 4

fluid-filled , unexpanded

Question 5

The umbilical arteries come off the ___ arteries and supply the placenta with oxygen.

Blood from the placenta returns to the foetus by the ___ ___.

Answer 5

iliac

umbilical veins

Question 6

In a foetus, there are three ___ which do not appear in adults.

Answer 6

shunts

Question 7

What is the ductus venosus?

Answer 7

Connects umbilical vein to the IVC

Question 8

What is the foramen ovale?

Answer 8

Opening in atrial septum which connects the right atrium to left atrium

Question 9

What is the ductus arteriosus?

Answer 9

Connects pulmonary bifurcation to the descending aorta

Question 10

Name the three shunts found in the foetal circulation.

Answer 10

Ductus venosus

Foramen ovale

Ductus arteriosus

Question 11

The ductus venosus carries the majority of placental blood straight into the ____, bypassing the ___ circulation.

Answer 11

IVC

portal

Question 12

The foramen ovale allows blood to flow from the ___ atrium to the ___ atrium.

Answer 12

right → left

Question 13

On which side of the heart is the foramen ovale’s membrane flap found?

Answer 13

Left side

Question 14

At the pulmonary bifurcation in a foetus, there are three possible pathways - name them and give their relative resistances.

Answer 14

Left pulmonary artery - high resistance

Right pulmonary artery - high resistance

Ductus arteriosus - low resistance

Question 15

The majority of oxygenated blood goes via the low-resistance ___ ___ to join the descending aorta.

Answer 15

ductus arteriosus

Question 16

Patency of the ductus arteriosus is maintained by ___ __.

Answer 16

Prostaglandin E2

Question 17

Where is Prostaglandin E2 produced?

Answer 17

Placenta

Question 18

Why are pregnant women advised not to take steroids?

Answer 18

Steroids interfere with Prostaglandin E2 which maintains the patency of the ductus arteriosus in their foetus

Question 19

In the first few minutes following birth, a baby undergoes many ___.

Answer 19

adaptations

Question 20

Following birth, a baby ___ their lungs and ___.

Answer 20

inflates , cries

Question 21

Following birth, a baby turns from ___ to ___.

Answer 21

blue , pink

Question 22

Following birth, the umbilical cord is ___.

Answer 22

cut

Question 23

Following birth:

pulmonary vascular resistance (increases / decreases)

systemic vascular resistance (increases / decreases)

Answer 23

Pulmonary resistance decreases

Systemic resistance increases

Question 24

Why does pulmonary resistance decrease following birth?

Answer 24

Baby starts to breath - lungs physically expand

Greater concentration of circulating oxygen - V/Q match, vasodilation

Question 25

Why does systemic resistance increase following birth?

Answer 25

**Umbilical cord is clamped and cut - all blood now part of the systemic circulation of the newborn**

Question 26

In a foetus, when the pressure of the __ atrium exceeds that of the ___ atrium, the ___ \_\_\_ closes.

Answer 26

**left \> right , closes**

Question 27

Following birth, the foramen ovale \_\_\_.

Answer 27

**closes**

Question 28

Why does the ductus arteriosus constrict following birth?

Answer 28

**Increased pO₂** **Placenta removed so Prostaglandin E2 no longer produced** **Reduced blood flow because pulmonary arteries are in use**

Question 29

Once the ductus arteriosus has completely closed, what is it called?

Answer 29

**Ligamentum arteriosum**

Question 30

Some congenital heart diseases cause \_\_\_-dependent circulation.

Answer 30

**duct**

Question 31

Give an example of a congenital heart disease in which the patency of the ductus arteriosus is vital to maintain life.

Answer 31

**Interruption of the aortic arch**

Question 32

What is given to maintain the patency of the ductus arteriosus while treatment for a duct-dependent circulation is figured out?

Answer 32

**IV prostaglandin E2**

Question 33

Pulmonary resistance reaches normal levels by ___ months.

Answer 33

**2-3 months**

Question 34

If a baby's pulmonary resistance doesn't decrease following birth, what disease do they have?

Answer 34

**Persistent pulmonary hypertension of the newborn**

Question 35

Persistent pulmonary hypertension is more likely to occur in ___ babies.

Answer 35

**sick**

Question 36

Persistent pulmonary hypertension can be caused by patent \_\_\_.

Answer 36

**ducts / shunts** see Slide 23 for illustration

Question 37

If a baby has persistent pulmonary hypertension, comparing the O₂ sats of the ___ and the ___ can help you confirm a \_\_\_-related cause.

Answer 37

**hand , foot , duct**

Question 38

Babies with PPHN will tend to be \_\_\_.

Answer 38

**blue**

Question 39

What can be inhaled to reduced pulmonary resistance? How?

Answer 39

**Nitric oxide - potent vasodilator**