Foramen ovale and inferior vena cavae

[sameeralord]

Hello everyone,

In fetal circulation most blood from inferior vena cavae go to left atrium via foramen ovale. This is not the case for superior vena cavae. But both drain into right atrium, so how is their a difference? Thanks

 

[bobze]

Hello everyone,

In fetal circulation most blood from inferior vena cavae go to left atrium via foramen ovale. This is not the case for superior vena cavae. But both drain into right atrium, so how is their a difference? Thanks

It has to do with the angle and pressure of the entering blood. Blood from the inferior vena cava is under greater pressure because it also contains the arterial blood of the umbilical artery. Where it enters the RA it is poised to open the "flap" made by the foramen ovale.

The point of this right-left shunt is to by pass the majority of the circulation to the pulmonary system which, prior to birth, doesn't need circulation.

 

[sameeralord]

It has to do with the angle and pressure of the entering blood. Blood from the inferior vena cava is under greater pressure because it also contains the arterial blood of the umbilical artery. Where it enters the RA it is poised to open the "flap" made by the foramen ovale.

The point of this right-left shunt is to by pass the majority of the circulation to the pulmonary system which, prior to birth, doesn't need circulation.

Good stuff. Thanks