Fetal circulation
Fetal circulation
- Oxygenated blood enters fetus from placenta via umbilical vein
- Blood enters IVC
- 50% directly through liver/hepatic sinusoids
- 50% via ductus venosus (later ligamentum venous in ligamentum teres)
- From IVC blood enters right atrium
- Passes through foramen ovale into left atrium, mixes with blood returning from lungs, ejected into left ventricle
- Passes into right ventricle, to pulmonary trunk then aorta via ductus arterious (later ligamentum arteriosus)
- Blood enters the aorta
- Half of blood enters umbilical arteries (medial umbilical ligament) for return back to placenta
Circulatory changes at birth
- Shunt closure
- FO closes (pressure effect)
- DV closes
- DA closes -
- Fall in pulmonary vascular resistance
- Following airation of lungs
- Rise in pulmonary blood flow
- Closure of umbilical vessels
