Zusammenfassung der Ressource
Circulatory changes at birth
- fetal circulation
- low left atrial Pa
- cos relatively little
blood returns from
lungs
- right atrial Pa> left atrial Pa
- right atrium
receives all sys
venous return incl
blood from placenta
- foramen ovale held open
- blood flows across atrial
septum from right to left
- w/ 1st few breaths
- resistance to pulmonary blood flow falls
- & blood vol flowing through lungs rises 6x
- so left atrial Pa increases
- placenta excluded from circulation
- so blood vol returning to right atrium falls
- change in Pa diff btw RA & LA
- -> foramen ovale closing
- ductus arteriosus
- connects pulmonary artery to aorta in fetal life
- normally closes in 1st few hours or days (day1-2)
- can remain open in some babies w/ congenital heart lesions
- called duct-dependent circulation
- clinical condition will worsen quickly when duct closes