Schema of foetal circulation.
The different colours indicate the oxygen content in the blood:
red = rich in oxygen,
blue = poor in oxygen,
purple = mixed blood.
Arrows indicate the direction of the blood flow.
S ho rt-circu it between the righ t and the left atrium
** S ho rt-circu it between the putm onary tru n k and the arch of aorta
* * * S ho rt-circu it between the um bilicat vein and the inferio r vena cava
Conversion from foetal to postnatal circulation:
The valve-like connection between the right and the left atrium via
the foram en ovale is passively closed at the onset of respiratory
activity in the lungs
** The ductus arteriosus IBOTALLO], on the other hand, closes only
during the firs t m onths of life as its lum en gradually obliterates by
epithelial proliferation and increased tension of the wait.
***T h e ductus venosus (ARANTIUS) obliterates a fte r birth and becomes
the tigam entum venosum in the portal area of the liver.