Breathing function
The placenta, which plays the role of «fetal lungs», is 15 times less efficient (with equivalent weight of tissue) than the real lungs.
The respiratory function of the placenta makes the fetal oxygen supply and fetal carbon dioxide removal possible.
The exchange takes place between maternal (oxygen-rich) blood and the blood of the Aa. umbilicales (mixing of arterial and venous blood, oxygen-poor). The oxygen goes via diffusion from the maternal into the fetal circulation system (PO2 maternal > PO2 fetal).
The carbon dioxide, the partial pressure of which is elevated in fetal blood, follows a reversed gradient.
Fetal, oxygen saturated blood, returns to the fetus via the umbilical vein, while maternal, oxygen-poor blood, flows back into the uterine veins.
The supply of the fetus with oxygen is facilitated by three factors:
- difference of oxygen concentration and partial pressure within the feto-maternal circulation system
- higher affinity of fetal hemoglobin (HbF) for oxygen
- l'effet Bohr
Summary:
Oxygen enrichment of fetal blood is promoted by concentration differences and partial pressure differences in the feto-maternal circulation, as well as by the larger affinity for oxygen to fetal HbF hemoglobin and the Bohr effect
Oxygen enrichment of fetal blood is promoted by concentration differences and partial pressure differences in the feto-maternal circulation, as well as by the larger affinity for oxygen to fetal HbF hemoglobin and the Bohr effect
.