Feto-placental circulation
Blood vessel enter chorionic plate underneath amnion.
2 Umbilical arteries
1 Umbilical vein
2 Umbilical arteries carry impure blood from fetus.
1 Umbilical vein carry oxygenated blood to fetus.
Three shunt in fetal circulation
Constrict after birth.
1. Ductus arteriosus
Connecting pulmonary artery with descending aorta, bypass pulmonary circulation.
Close first 72 hours after birth.
2. Ductus venous
Fetal blood vessel connecting umbilical vein to IVC (inferior vena cava).
3. Foramen ovale
Shunts highly oxygenated blood from right atrium to left atrium (most oxygenated blood).
Ductus venous - through IVC - Right atrium - through foramen ovale - left atrium
Oxygenated rich red blood cell get from placenta to fetal tissue.
Blood from placenta highly oxygenated, color red.
From the placenta, oxygenated blood get through umbilical vein carried oxygenated blood towards liver.
When umbilical vein reaches the liver, bypass liver from shunt ductus venous towards oxygenated blood inferior vena cava(IVC).
Oxygenated blood reaches right atrium via IVC and enter left atrium via patent foramen ovale.
Rich oxygen blood go from right atrium to left atrium then left ventricle.
And left ventricle to aorta, by pass lung and send to systemic circulation and leave poor oxygenated blood through umbilical arteries and get back to placenta to pick up oxygen.
(Very little less oxygenated blood mix with oxygenated blood).
Poor blood return to right atrium through superior venacava.
Less oxygenated blood pumped from right ventricle into left pulmonary artery.
Less oxygenated blood shunted through ductus arteriosus to descending aorta.
Then enters the umbilical cord and flow into placenta.
In placenta CO2 and waste product released.
Fetal blood flow through placenta; 400ml per minute
Pressure in umbilical artery; 60mmHg
Pressure in umbilical vein; 10mmHg
Fetal capillary pressure in villi; 20-40mmHg
Umbilical artery Umbilical vein
O2 saturation 50-60% 70-80%
PCO2 20-25mmHg 30-40mmHg
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