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 bypassing 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
