Fetal Circulation – outline notes

The lungs of a fetus are non-functional. There are special structures that allow blood flow to bypass the fetal lungs. Not until birth do the lungs gain their normal function.

Umbilical Cord
–Umbilical Vein – high Oxygen and nutrients from mother to fetus
–Umbilical Arteries (two) – Carbon dioxide and waste from fetus to mother

Pathway of Blood in Fetus

High Oxygenated blood from mother flows through umbilical vein to fetal heart
 -some perfuses liver
-most goes to inferior vena cava via ductus venosus and then to R. Atrium

Blood can take two paths, ultimately to bypass non-functional fetal lungs

1. Right atrium —- foramen ovale —- Left atrium —- aorta —- systemic circulation —- umbilical
arteries —– placenta

2. Right atrium —- Right ventricle —- pulmonary trunk —- ductus arteriosus —- aorta —- umbilical
arteries —- placenta

*foramen ovale and ductus arteriosus are special structures that allow for specific fetal blood flow.

After Birth
–foramen ovale becomes fossa ovalis
–ductus arteriosus becomes ligamentum arteriosum