Fetal erythropoiesis and circulation Flashcards
What is the order of organs in which fetal erythropoiesis occurs?
Yolk Sac, Liver, Spleen, Bone
When does fetal erythropoiesis occur in the yolk sac?
3-8 weeks
When does fetal erythropoiesis occur in the liver?
6 weeks-birth
When does fetal erythropoiesis occur in the spleen?
10-28 weeks of development.
When does erythropoiese occur in the bone marrow?
18 weeks of development to adult.
Do embryos have different hemoglobins?
Yes weird little funky guys. Two zeta chains, two epsilon chains.
What is fetal hemoglobin composed of?
Two alphas, two gammas.
What is adult hemoglobin composed of?
Two alphas, two betas.
How does HbF manage to extract oxygen from maternal hemoglobin across the placenta?
It has a greater affinity for oxygen.
What does 2-3BPG have to do with hemoglobin?
2,3BPG is an allosteric effector in the relationship between hemoglobin and oxygen. With adult hemoglobin, it binds better to deoxygenated hemoglobin than oxygenated hemoglobin. When it binds to a hemoglobin who has already lost some oxygen, it promotes the release of remaining oxygen molecules for delivery to the tissues.
Where is 2-3BPG produced?
In the RBCs by 2-3BP Mutase. Skips an ATP-producing step in glycolysis, but favors greater oxygen delivery to tissues.
What does 2-3BPG have to do with fetal hemoglobin?
Has a lower affinity for fetal hemoglobin, so it allows for HbF to extract O2 from maternal HbA across the placenta.
What happens to HbF after birth?
Drops down. Replaced by HbB.
Where is oxygen saturation highest in fetal circulation?
Umbilical vein coming from placenta.
Where does blood from the umbilical vein first go through and why?
The ductus venosus, which connects umbilical vein to IVC and bypasses hepatic circulation.
Once through the ductus venosus, where does fetal blood go?
To the right atrium.
Where does oxygenated blood entering the right atrium go?
Through the foramen ovale, connecting to the left atrium, then left ventricle and out the ascending aorta to supply the brain.
Where does deoxygenated blood from the SVC go?
Enters the right atrium, down to right ventricle, into main pulmonary artery, and through patent ductus arteriosis
What is the ductus arteriosus?
Connects the pulmonary artery with the descending aorta, thereby bypassing the lungs (blood comes in from RV –> pulmonary artery –> ductus arteriosus –> descending aorta).
Why does blood mostly go through the ductus arteriosus down the descending aorta instead of through the pulmonary artery?
There is very high pulmonary artery resistance due to low oxygen tension.
But does ALL of the blood go through the ductus?
No a little goes through the pulmonary arteries and then comes back through pulmonary veins into left atrium, where it meets the oxygenated blood coming in from the foramen ovale.
So, the blood leaving the left ventricle via the ascending aorta, how oxygenated is it?
Partially oxygenated.
What is the first thing that happens when the infant is born and takes a breath?
Decrease in pulmonary resistance. This allows increased pulmonary artery flow and decreased flow across the ductus arteriosus.
Why does left atrial pressure increase after birth?
With increased pulmonary artery flow, there is increased pulmonary vein flow –> increased blood flow into the left atrium
