2: Foetal circulation and adaptation at birth Flashcards
The ___ is responsible for fetal ___.
placenta , homeostasis
What maintains the patency of the ductus arteriosus when a baby is in utero?
Prostaglandin E2
What is the site of gas exchange, nutrition, waste excretion and homeostasis in a foetus?
Placenta
In a foetus, the lungs are ___-filled and ___.
fluid-filled , unexpanded
The umbilical arteries come off the ___ arteries and supply the placenta with oxygen.
Blood from the placenta returns to the foetus by the ___ ___.
iliac
umbilical veins
In a foetus, there are three ___ which do not appear in adults.
shunts
What is the ductus venosus?
Connects umbilical vein to the IVC
What is the foramen ovale?
Opening in atrial septum which connects the right atrium to left atrium
What is the ductus arteriosus?
Connects pulmonary bifurcation to the descending aorta
Name the three shunts found in the foetal circulation.
Ductus venosus
Foramen ovale
Ductus arteriosus
The ductus venosus carries the majority of placental blood straight into the ____, bypassing the ___ circulation.
IVC
portal
The foramen ovale allows blood to flow from the ___ atrium to the ___ atrium.
right → left
On which side of the heart is the foramen ovale’s membrane flap found?
Left side
At the pulmonary bifurcation in a foetus, there are three possible pathways - name them and give their relative resistances.
Left pulmonary artery - high resistance
Right pulmonary artery - high resistance
Ductus arteriosus - low resistance
The majority of oxygenated blood goes via the low-resistance ___ ___ to join the descending aorta.
ductus arteriosus
Patency of the ductus arteriosus is maintained by ___ __.
Prostaglandin E2
Where is Prostaglandin E2 produced?
Placenta
Why are pregnant women advised not to take steroids?
Steroids interfere with Prostaglandin E2 which maintains the patency of the ductus arteriosus in their foetus
In the first few minutes following birth, a baby undergoes many ___.
adaptations
Following birth, a baby ___ their lungs and ___.
inflates , cries
Following birth, a baby turns from ___ to ___.
blue , pink
Following birth, the umbilical cord is ___.
cut
Following birth:
pulmonary vascular resistance (increases / decreases)
systemic vascular resistance (increases / decreases)
Pulmonary resistance decreases
Systemic resistance increases
Why does pulmonary resistance decrease following birth?
Baby starts to breath - lungs physically expand
Greater concentration of circulating oxygen - V/Q match, vasodilation
Why does systemic resistance increase following birth?
Umbilical cord is clamped and cut - all blood now part of the systemic circulation of the newborn
In a foetus, when the pressure of the __ atrium exceeds that of the ___ atrium, the ___ ___ closes.
left > right , closes
Following birth, the foramen ovale ___.
closes
Why does the ductus arteriosus constrict following birth?
Increased pO2
Placenta removed so Prostaglandin E2 no longer produced
Reduced blood flow because pulmonary arteries are in use
Once the ductus arteriosus has completely closed, what is it called?
Ligamentum arteriosum
Some congenital heart diseases cause ___-dependent circulation.
duct
Give an example of a congenital heart disease in which the patency of the ductus arteriosus is vital to maintain life.
Interruption of the aortic arch
What is given to maintain the patency of the ductus arteriosus while treatment for a duct-dependent circulation is figured out?
IV prostaglandin E2
Pulmonary resistance reaches normal levels by ___ months.
2-3 months
If a baby’s pulmonary resistance doesn’t decrease following birth, what disease do they have?
Persistent pulmonary hypertension of the newborn
Persistent pulmonary hypertension is more likely to occur in ___ babies.
sick
Persistent pulmonary hypertension can be caused by patent ___.
ducts / shunts
see Slide 23 for illustration
If a baby has persistent pulmonary hypertension, comparing the O2 sats of the ___ and the ___ can help you confirm a ___-related cause.
hand , foot , duct
Babies with PPHN will tend to be ___.
blue
What can be inhaled to reduced pulmonary resistance? How?
Nitric oxide - potent vasodilator
