Embryology - Foetal Circulation and Adaptation Flashcards
What are the main functions of the placenta?
Foetal homeostasis Gas exchange Nutrient transport to foetus Waste product transport Hormone production of Prostaglandin E Transport of IgG. Slide 4
How does foetal circulation differ to adult circulation?
Adults cirulation is in a ‘figure of 8’ shape and goes to lungs and body.
The foetal circulation is a circle mainly going to the placenta to be oxygenated and to the rest of the body with a small amount going to the lungs to aid developement. Slide 7
What carries the blood from the foetal heart to the placenta and which carries the oxygenated blood?
Umbilical arteries and umbilical veins
However, the arteries carry the deoxygenated blood and the veins carry oxygenated blood. Slide 8
What are the 3 shunts specific to foetal life?
Ductus venosus: Connects umbilical vein to the inferior vena cava.
Foramen Ovale: Opening in atrial septum connecting RA and LA.
Ductus Arteriosus: Connects pulmonary bifurcation to the descending aorta. Slide 10
Which side is the membrane flap of the foramen ovale on of the heart and what causes the blood to flow through it?
It is on the left atrium side: due to the pressure on the Right atrium being higher than the left, the blood is pushed through foramen ovale. Slide 12
What is the function of the ductus arteriosus and how is it kept open?
Allows the some of the blood to travel into the pulmonary arteries to the lungs and is kept open by prostaglandin E2. Slide 13
What are the circulatory changes a baby goes through when they are born?
The pulmonary vascular resistance decreases when they breath in allowing the lungs to expand, so blood can be oxygenated.
The systemic vascular resisitance rises dramatically due to the cord beign clamped. This causes increase CO to the lungs. Slide 16
How does the foramen ovale close?
Due to the changes in pressure of circulation when the baby is born, now the left sided atrium is much higher pressure than the right causing the flap to be pushed closed. Slide 17
What happens to the ductus arteriosus when the baby has been born and how?
It constricts.
This is a rare part of smooth muscle which constricts when exposed to oxygen. So when the baby breathes the O2 acts as a vasoconstrictor. There is also a decrease of flow across it and the loss of prostaglandin stimulation. Slide 18
When the the ductus arteriosus maybe no close and what would the treatment be?
In very premature babies
Use NSAIDS e.g. ibuprofen which inhibits prostaglandin
Surgery. Slide 19
When would you want to keep the ductus arteriosus open and how would you?
If the newborn had a heart disease that was duct dependent for
circulation.
IV prostaglandin E2 is administered to keep it open until there is an alternative shunt or dinifitive surgery. Slide 20
When does pulmonary resistance reach normal adult type levels?
By 2-3 months. Slide 21
What is PPHN and when could it occur?
Persistent pulmonary hypertension of the newborn; the pulmonary resistance doesn't fall so the shunts remain open and there is mixing of blood. Occurs in very sick babies: Sepsis Hypoxic ischaemic insult Meconium aspiration syndrome Cold stress. Slide 22+23
How can you tell a baby has PPHN and what is the treatment?
They have a large difference in pre and post ductal O2 sats so check the sats on right hand and feet.
The treatment is supportive; ventilation, O2, inotropes to increase systemic BP, inhaled NO and ECLS for severe cases. Slide 24
