Sometimes I like to draw on things that aren’t cylindrical:
In preparation for our pediatrics exam yesterday morning, I decided delve a little deeper into fetal circulation.
So these little guys have circulation way more complicated in the womb than after they are born. This is because mom (and her placenta) are doing the work for the baby’s lungs. Oxygen rich blood travels from the placenta to the fetus through the umbilical vein, first it passes through the baby’s liver and then over to the right side of the heart. Now in you or I, the blood from the right side of the heart is pumped into our lungs to get oxygen…but baby has already got all the O2 it needs from mom, so it is pushed through a small hole between the top two chambers of the heart (right and left atrium). This is called the foramen ovale and it will close after the baby is born. This hole allows the red 02 rich blood to go from the right atrium to the left atrium, then to the left ventricle and out the aorta. This allows the most oxygen right blood to get right up to the brain!
When the blood comes back to the fetus’s heart, it enters the right atrium again. The blood exits the right ventricle, bypassing the lungs through the second extra hole in fetal circulation called the ductus arteriosus. The bluer blood circulated through the lower half of the fetus’s body and then leaves through the umbilical arteries…back to mom to get some more O2.
Pretty fascinating eh?
Curious for more, here is a pretty in depth animation and discussion of the process!