x exam 2 fetal circulation Flashcards
peculiarities of fetus
nonfunctional lungs that are highly resistant to blood flow
O2/CO2 nutrient/waste exchange all occur at placenta (liver)
cirulatory needs of fetus
blood to and from placenta
bypass non functional organs (lungs and liver)
maximize quality nutrients and O2 content to developing nervous system
umbilical arteries
blood to placenta; branches of caudal most pair of lumbar intersegmental arteries
umbilical vein
blood from placenta; left umbilical vein joins ductus venosus (high oxygen and nutrient content)
ductus venosus
bypass liver (hepatic circulation); connects umbilical v. and hepatic protal v. to caudal vena cava
foramen ovale
bypass lungs; connects right atrium to left atrium
ductus arteriosus
maximize nutrient and o2 rich blood to developing CNS; connects pulmonary trunk to aorta caudal to branches that give rise to common caroitid aa.
fetal circulation pattern
right to left shunting; preserve highest oxygen content and nutrient rich blood and direct it to the developing CNS
Key event at birth
respiration with O2/CO2 exchange in lungs begins
consequences of birth: lungs inflate which causes
decreased pulmonary resistance
increased pulmonary flow
decresed pressure in right atrium, increased pressure in left atrium
functional closure of foramen ovale
consequences of birth: increased pO2
dilation pulmonary aa
constirction smooth muscles with umbilical aa, umbilical v, ductus venosus, and ductus arteriosis; functional closure preventing blood flow through structures
physical stretching and reflex smooth muscle constriction may also contribute to
closure of umbilical vessels
overtime functional closurs are made
permanent and replaced with connective tissue
umbilical arteries becomes
round ligament of urinary bladder
umbilical vein
round ligament of liver
