Flashcards in Fetal Circulation and Physiology Deck (60):
n the fetus, some organs do not function until birth
Kidneys GI Tract
Fetus obtains oxygen and nutrients
via diffusion from the maternal blood.
Wastes and CO2 are eliminated via
diffusion into the maternal blood
waste and oxygen exchange occurs via
the placenta Inside the uterus Attached to baby via the umbilical cord
way of communication between mother and baby
Site of exchange of nutrients/ wastes
carries blood away from the fetus to
the placenta Carries wastes and CO2 LOW O2 Content!
carries blood from the placenta to the fetus
Carries nutrients and O2 HIGH O2 Content
Umbilical arteries and veins branch into these capillaries located inside the intervillous spaces in the placenta.
Spaces filled with maternal blood from uterine arterioles. Drained by Uterine veins.
The placenta communicates with the mother’s cardiovascular
uterine blood vessels.
waste from placenta
diffuse out of the capillaries into the intervillous spaces
containing maternal blood in the placenta.
Nutrients travel from mother’s blood vessels
to the intervillous space via uterine arteries. Diffuse from the intervillous spaces into the fetal capillaries
The concentration of hemoglobin in fetal blood is about
than maternal blood
Fetal hemoglobin has a greater affinity for oxygen than maternal blood
30-35% more O2
THERE IS NO DIRECT MIXING
OF MATERNAL AND FETAL BLOOD!!!
The Placenta - Function Exchange of gases – CO2, O2, CO
Accomplished via diffusion 20-30mL O2/min extracted Short interruption in blood flow can be fatal to fetus Depends on delivery not rate of diffusion
The Placenta - Function Exchange Nutrients/ Electrolytes
Amino Acids, Free Fatty Acids, Carbohydrates, Vitamins Exchange is rapid and increases as pregnancy increases
Placental circulation has a very low
The Placenta - Function Transfer of Maternal Antibodies
Late first trimester – fetus makes components of complement
Start of immunological competence
The Placenta - Function mmunoglobulins – Primarily IgG
Transported from mother to fetus (at about 14 weeks)
Provides passive immunity
Newborns produce own IgG, but don’t reach adult levels until about age 3.
The Placenta - Function
4th month – placenta produces enough progesterone
to support pregnancy, should corpus luteum fails
Continues to produce estrogenic hormones Estriol
Rises until end of pregnancy
Umbilical Blood Vessels Blood passes from the fetus to the placenta via________ THAT BRANCH OFF______ WITH a sat. of______
Branch of the internal iliac arteries Sat ~58%
Oxygenated blood returns from the placenta via ______ with a sat_______
1 umbilical vein with a sat of 80%
oxygenated blood goes to the liver where it branches into
Joins hepatic portal vein -> Liver (1/3)
Ductus Venosus -> IVC (2/3)
Sphincter mechanism in ductus that controls blood flow through the liver
n the IVC, oxygenated blood via the______ and sat falls to
ductus venosus meets deoxygenated blood from the lower body. Sat falls to about 67%
fetal lung fluid. Not used to oxygenate blood. This liquid increases the pulmonary vascular resistance to blood flow
Most fetal blood does not go from
the RV to the lungs
Most fetal blood passes through
Foramen Ovale Hole between the Right and Left Atria. Blood entering from the IVC is guided toward the foramen ovale to the Left Atrium.
In the LA, blood mixes
with the very small amount of blood returning from the pulmonary veins
Goes to the LV LV pumps the oxygenated blood into the aorta Perfuses the brain and myocardium Getting highest O2 content available
Fetal blood returning to the heart from the SVC
bypasses the Foramen Ovale and enters the RA
Goes to the RV and pumped to the PA
Pulmonary Vascular Resistance is so high that
95% of this
blood bypasses the pulmonary arteries Travels across the ductus arteriosus to the descending aorta Ductus arteriosus connects PA and Aorta
Perfuses fetal tissues
At the common iliac branch to the internal and external iliacs
Part of that blood flowing systemically will
low through the internal iliacs to the umbilical artery
Will go to the placenta for nutrient/waste exchange
The only fetal vessel to carry fully oxygenated blood is the
Blood entering the aorta from the LV and perfusing the head and heart has
a higher oxygen content than the blood perfusing the rest of the body.
There are 3 shunts present in the fetal circulation that normally close after birth:
Ductus Arteriosus Foramen Ovale Ductus Venosus
At birth, the _________ start to function.
Pulmonary, Renal and Digestive Systems
Umbilical Arteries Contraction of
smooth muscle in walls
Likely caused by thermal and mechanical stimuli and change in oxygen tension
Umbilical Arteries functionally
close a few minutes after birth
Eventually will fill with connective tissue
umbilical arteries distal portion after birth will become
fibrous cords Medial umbilical ligaments
umbilical arteries fully close
2-3 months after birth
Collapses shortly after
the umbilical arteries
Blood from the placenta may enter newborn for some time after birth.
umbilical vein Remains as the
as the ligamentum teres hepatis
Lower margin of the falciform ligament. Attaches the umbilicus to the liver
Remains as Ligamentum Venosum Fibrous cord on the inferior surface of the liver
Patent Ductus Venosus is
extremely rare Less than 20 reported world wide
Usually______ due to
closes after birth to become the Fossa Ovalis
The first breath causes the lungs to expand and blood flow to the lungs increases. Blood returning to the LA increases the pressure in the LA And pressure in the RA falls.
First breath presses
the septum primum against the septum secundum
causes functional closure of the foramen ovale at birth.
First days of life, closure
Crying by baby creates a right to left shunt and can account for the cyanotic periods of newborns.
Constant apposition leads to
fusion of the septa
Anatomical (permanent) closure o septa occurs within
After a year, if the Foramen Ovale has not closed
it is referred to as a Patent Foramen Ovale (PFO).
prevalence of PFO
27%. patients are usually asymptomatic
ontraction of the muscular wall immediately after birth. Mediated by Bradykinin which is released by the lungs during the initial inflation.
ductus arteriosis closes in
1-2 days. small shunt of blood from the Aorta to the left PA for a few days
small shunt of blood from aorta to PA becomes
omplete obliteration of the lumen
takes 1-3 months.
Umbilical Arteries becomes
– Medial Umbilical Ligaments
Ligamentum Teres (Round Ligament
ductus venosus becomes
foramen ovale becomes