Week 5/6 - G - V. Summarised Foetal Circulations - umbilical vessels, ductus venosus, foramen ovale, ductus arteriosus Flashcards
The placenta has a lot of functions during pregnancy to assist with the foetal circulation - * Gas exchange * Exchange of nutrients and waste * Homeostasis How does the foetal heart pump blood to the placenta and why? How is the blood from the placenta returned to the foetus?
The foetal heart pumps deoxygenated blood to the placenta via the umbilical arteries The blood from the placena is returned, oxygenated, via the umbilical vein
The oxygenated, nutrient rich blood returns from the placenta to the right side of the heart and needs to be distributed to the growing foetus What are the 3 shunts that are specific to foetal life?
Ductus venosus Foramen ovale Ductus arteriosus
How do the three aforementioned shunts work?
DV allows the oxygenated blood to bypass the foetal liver and connects directly to the inferior vena cava FO is an opening in the atrial septum- connects the RA to LA allowing the oxygenated blood to bypass the immature foetal lungs DA connects the pulmonary birfurcation to the descending aorta - again bypassing the lungs
Why does the majority of foetal blood not need to go to the liver? Where does the best oxygenated blood that enters through the foramen ovale go?
Majority of foetal blood does not need to go to the liver as it has already recieved the nutrients from the placenta The best oxygenated blood that passes through the foramen ovale is able to enter the LA, LV then ascending aorta and then carotids to the brain
What is the valve known as that directed the oxygenated blood coming into the right atrium from the inferior vena cava towards the foramen ovale known as?
This is known as the eustachian valve (valve of the inferior vena cava)
What percentage of the RV output actually goes to the foetal lungs? Where does the rest go? What maintains the patency of this structure during pregnancy?
only 7% of the RV output goes to the lungs and the rest goes via the ductus arteriosus to join the descending aorta Patency of the ductus arteriosus is maintained by circulating prostoglandin E2 produced by the placenta
What is the remnant in adults known as: * umbilical veins? * ductus venosus? What lobe of the liver does each separate?
Fibrous remnants Umbilical veins becomes ligamentum teres (round ligament) - separates the quadrate lobe from the left lobe of the liver Ductus venosus becomes ligamentum venosum - separates the cuadate lobe from the left lobe of the liver
What is the remnant in adults known as: foramen ovale? ductus arteriosus?
Fibrous remnants foramen ovale becomes known as the fossa ovalis - when left atrial pressure exceeds the right atrial pressure the shunt closes ductus arteriosus becomes known as the ligamentum arteriosum - due to decrease in flow and PGE2 (placenta no longer producing it)
In some babies the ductus arteriosus fails to close Which type of baby is this more common in? What can be given prophylactically to the mother? What are the treatment options?
More common in preterm infants Can give dexamethasone prophylactically to the mother, helps to close the ductus arteriosus Medical management to close the duct is usually IV NSAIDs - indoemtacin or ibuprofen (since they both inhibit prostoglandin synthesis) given to the baby Surgery is the other option
Some congenital heart diseases cause a duct dependent circulation - Give an example of a case where this happens?
This could happen in transposition of the great arteries, hyopplastic left heart, critical aortic stenosis, interuppted aortic arch etc - where PA is coming from LV and aorta is coming from RV Can give IV prostoglandin E1 or E2 to keep the duct open until an alternative shunt established or definitive surgery carried out
When a baby is born, congenital heart disease is the most common type of birth defect Broadly categorised as cyanotic and acyanotic heart defects What are the causes?
Cyanotic causes Respiratory causes Cardiac causes - anything that causes a right to left shunt * Transposition of the great arteries * Tetralogy of Fallot * Persistent pulmonary hypertension of the newborn
