Foetal Circulation Flashcards
how are oxygen and nutrients supplied to the foetus
- placenta
the foetal heart and blood vessel are essential to carry ___ and ____ to foetal ____ & to remove ____
- oxygen and nutrients
- to foetal tissues
- remove waste
how does nutrient supply from the placenta enter
- via umbilical veins
what is present in the foetal circulation that allow different pattern of blood flow in foetus compared to adult
three shunts
name of the three shunts
- ductus venosus
- ductus arteriosis
- foramen ovale
location of the ductus venosus
in the liver circulation
between umbilical vein and inferior vena cava
function of ductus venosus
- allows o2 and nutrient rich blood, coming form the placenta in the umbilical cord, to mostly bypass the foetal liver, diverting blood into inferior vena cava which leads to the foetal heart
why is the ductus venosus able to mostly bypass the foetal liver blood supply
- immature foetal liver plays smaller role in metabolism than it does in adult
- only requires a small flow of blood to meet its needs
replenished blood from the placenta flowing through the ductus venosus mixes with what
foetal venous blood returning through foetal veins to the heart
the non-inflated foetal state means what for the foetal lungs
they are non-functional
due to non-inflated state, resistance to blood flow in pulmonary circulation is ____
very high
how are foetal lungs bypassed
- majority of highly oxygenated foetal blood from inferior vena cava is shunted directly from right atrium into left atrium thru foramen ovale
what blood mixes in left atrium from expected and shunted blood
- deoxygenated blood from pulmonary vein that has travelled through developing lungs
- oxygenated blood from right atrium through foramen ovale
describe the rest of the normal blood supply from heart after left atrium
blood in left atrium -> moves to left ventricle -> pumped into aorta -> supplies foetal tissues and organs
how is foetal heart and foetal brain supplied with blood
same as others from being pumped into aorta
- goes to heart via coronary arteries
- goes to brain via carotid arteries
why is the blood from the IVC going into the right atrium mostly oxygenated blood
- due to the ductus venosus
- oxygenated blood coming from placenta is being diverted to IVC and to heart
why is blood coming from the pulmonary veins not oxygenated blood
because the lungs are non-functional so are not oxygenating them as they are developing
where does the remaining blood in the right atrium of the heart go
pulmonary artery
which is standard for adult circulation
does the blood that goes into pulmonary artery go to the foetal lungs
- some does
- able to bypass lungs by entering ductus arteriosus
what does the ductus arteriosus connect
- pulmonary artery with the aorta
what does resistance to blood flow in the pulmonary circulation is very high mean
it is difficult for blood to pass through the blood vessels in the lungs
why is flow into the aorta favoured over the foetal lungs
- because the aorta has low resistance
- high resistance in foetal pulmonary vessels
why
deoxygenated blood normally comes from IVC
so the normal blood in the RA is deoxygenated if its not from the ductus venosus
some of the RA blood will go via the ductus arteriosis to the aorta and still be deoxygenated
some of the RA blood will go to the lungs and still be deoxygenated and be in left atrium where ends up in aorta deoxygenated (normal route except lungs not functioning so not oxygenated)
why is blood flowing through the descending aorta a mix of oxygenated blood and partly deoxygenated blood
- oxygenated blood from placenta that has been through ductus venosus and foramen ovale or ductus venosus and ductus arteriosus
- deoxygenated blood that has been passed thru foetal tissues (removed nutrients too)
after blood has been circulated from the descending aorta to the foetal tissues, how does it return to the placenta
- branches of the internal iliac arteries flow into the two umbilical arteries to return this blood to placenta
why is blood returned to the placenta
- replenished with oxygen and nutrients from maternal circulation
