Foetal circulation and adaptation at birth Flashcards
Which functions is the placenta included in?
Foetal circulation
Gas exchange
Nutrition
Waste excretion
Homeostasis
Via which artery does blood travel from the foetal heart to the placenta?
The umbilical arteries
Via which vein does blood travel from the placenta to the foetus?
The umbilical vein
What are the 3 shunts of the foetal circulatory system?
Ductus venosus
Foramen ovale
Ductus arteriosus
What is the function of the ductus venosus?
It connects the umbilical vein to the inferior vena cava, bypassing the hepatic system and liver
What is the function of the foramen ovale?
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
What is the function of the ductus arteriosus?
It connects the pulmonary artery to the aorta, allowing some of the blood that passes into the right ventricle to return to the aorta
What keeps the ductus arteriosus open?
Prostaglandin E2
Where is prostaglandin E2 produced?
In the placenta
How is blood directed through the foramen ovale?
The musculi pectinati (Pectinate muscles) in the auricle of the right ventricle direct blood into the foramen ovale
What is the average saturation rate of a foetus?
~70%
What are the 2 major adaptations to circulation after birth?
Cutting of the umbilical cord increases SVR
First breaths and crying introduces oxygen, which is a potent vasodilator, which decreases pulmonary vascular resistance
What causes the closure of the foramen ovale?
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
What causes closure of the ductus arteriosus?
Decrease in prostaglandin levels
Decreased flow due to pressure differences
Oxygen levels rise, reacting with the oxygen sensitivity muscular layer in the ductus arteriosus
What does closure of the ductus arteriosus form?
The ligament arteriosum
What condition occurs when the ductus arteriosus does not close?
Patent ductus arteriosus
What is the treatment for patent ductus arteriosus?
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
What is meant by interruption of the aortic arch?
The aortic arch is closed off at one point and the descending aorta is only fed by the ductus arteriosus
What is the main treatment for interruption of the aortic arch?
IV prostaglandin E2 and then surgery with a stent
What are some conditions that can increase likely hood of persistent pulmonary hypertension of the newborn?
Sepsis
Hypoxic ischaemic insult
Meconium aspiration syndrome
Cold stress
What is the cause of persistent pulmonary hypertension of the newborn?
The pulmonary vascular resistance doesn’t decrease and stays high, meaning lung pressure is greater than SVR
