8. Fetal Circ- Exam 2 Flashcards
what organs do not function until birth
lungs
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
where does exchange occur
Exchange occurs via the placenta
Inside the uterus
Attached to baby via the umbilical cord
Placenta –
way of communication between mother and baby
Site of exchange of nutrients/ wastes
Umbilical Artery –
carries blood away from the fetus to the placenta
Carries wastes and CO2
LOW O2 Content!
Umbilical Vein –
carries blood from the placenta to the fetus
Carries nutrients and O2
HIGH O2 Content
Fetal Capillaries –
Umbilical arteries and veins branch into these capillaries located inside the intervillous spaces in the placenta.
Intervillous Spaces –
Spaces filled with maternal blood from uterine arterioles. Drained by Uterine veins.
The placenta communicates with the mother’s cardiovascular system via
uterine blood vessels.
where does waste diffuse out of and what does it contain
Wastes 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
Nutrients travel from mother’s blood vessels to the intervillous space via uterine arteries into the fetal capillaries–describe the fetal hgb at this point
The concentration of hemoglobin in fetal blood is about 50% higher than maternal blood
- -Fetal hemoglobin has a greater affinity for oxygen than maternal blood
- -Can carry 30-35% more oxygen.
is there direct mixing of maternal and fetal blood through the placenta
THERE IS NO DIRECT MIXING OF MATERNAL AND FETAL BLOOD!!!
what are the functions of the placenta
Exchange of gases – CO2, O2, CO (diffusion)
Exchange Nutrients/ Electrolytes
Transfer of Maternal Antibodies
Hormone Production
describe diffusion of gases across the placenta
20-30mL O2/min extracted
Short interruption in blood flow can be fatal to fetus
Depends on delivery not rate of diffusion
what nutrients/electrolytes are exchanged
Amino Acids, Free Fatty Acids, Carbohydrates, Vitamins
Exchange is rapid and increases as pregnancy increases
describe the placentas circulation resistance
very low resistance
when does Transfer of Maternal Antibodies start to take place
Late first trimester – fetus makes components of
complement
-Start of immunological competence
what immunoglobulin is primarily made? when is transfered to the fetus? what does it provide?
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 what age
3
when does the placenta produces enough progesterone
to support pregnancy, should corpus luteum fails
4th month
that kind of hormones does the placenta continue to produce
Continues to produce estrogenic hormones
- Estriol
- Rises until end of pregnancy
Blood passes from the fetus to the placenta via? whats the sat?
2 umbilical arteries
Branch of the internal iliac arteries
Sat ~58%
Oxygenated blood returns from the placenta via? whats the sat?
1 umbilical vein
Sat ~80%
after the Oxygenated blood returns from the placenta via 1 umbilical vein- where does it go? what branches? what controls blood flow?
Goes to the liver of the fetus where it divides into 2 branches
- Joins hepatic portal vein -> Liver (1/3)
- Ductus Venosus -> IVC (2/3)
- Sphincter mechanism in ductus that controls blood flow through the liver
In the IVC, oxygenated blood via the ductus venosus meets deoxygenated blood from the lower body. What does the sat falls to about?
67%
describe the fetal lungs
Filled with fetal lung fluid
Not used to oxygenate blood
what is the purpose of the fluid in the fetal lungs
This liquid increases the pulmonary vascular resistance to blood flow
Most fetal blood does NOT go from the RV to the lungs. What does it do instead
- -Instead, it passes through the 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 _____ amount of blood returning from the pulmonary veins
small
after blood pass through the LA, where does it go next? what the purpose?
Goes to the LV and the oxygenated blood is pumped into the aorta
- -Perfuses the brain and myocardium
- -Getting highest O2 content available
Fetal blood returning to the heart from the SVC bypasses the ______ and enters the RA
Foramen Ovale
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. describe PVR at this point and what it causes
PVR 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 flow where?
through the internal iliacs to the umbilical artery
-Will go to the placenta for nutrient/waste exchange
what is the only fetal vessel to carry fully oxygenated blood?
umbilical vein
Blood entering the aorta from the LV and perfusing the head and heart has what level of O2 content
higher oxygen content than the blood perfusing the rest of the body
At birth, what Systems start to function
Pulmonary, Renal and Digestive
what 3 shunts present in the fetal circulation normally close after birth
Ductus Arteriosus
Foramen Ovale
Ductus Venosus
Umbilical Arteries: Contraction of smooth muscle in walls is ikely caused by
thermal and mechanical stimuli and change in oxygen tension
when do Umbilical Arteries lose functionality
a few minutes after birth
Complete closure takes 2-3 months
what will Umbilical Arteries eventually fill with after birth
connective tissue
the distal portion of the Umbilical Arteries will become what
fibrous cords
-Medial umbilical ligaments
when does the Umbilical Vein collapse
shortly after the umbilical arteries
Can blood from the placenta enter the newborn (via Umbilical Vein) for some time after birth?
yes
Umbilical Vein remains as what after birth
Remains as the ligamentum teres hepatis
-Lower margin of the falciform ligament. Attaches the umbilicus to the liver
what does the Ductus Venosus do after birth? what does it become?
Collapses
- Remains as Ligamentum Venosum
- -Fibrous cord on the inferior surface of the liver
what is the occurrence of Patent Ductus Venosus’s
extremely rare
Less than 20 reported world wide
what happend to the Foramen Ovale after birth? what does it become?
Usually closes after birth to become the Fossa Ovalis
describe how the Foramen Ovale closes
- 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 which causes functional closure of the foramen ovale at birth
- Constant apposition leads to fusion of the septa
Foramen Ovale closure is reversible in the first days of life. How is this possible?
Crying by baby creates a right to left shunt and can account for the cyanotic periods of newborns
when does Anatomical (permanent) closure occur for the Foramen Ovale
within the first year of life.
After a year, if the Foramen Ovale has not closed, it is referred to as a:
Patent Foramen Ovale (PFO).
Autopsy studies show a __% prevalence of PFO
Most patients are _________
27%
asymptomatic
when does the Ductus Arteriosus close? what mediated this?
- Closes via contraction of the muscular wall immediately after birth.
- Mediated by Bradykinin which is released by the lungs during the initial inflation
describe how the Ductus Arteriosus closes
- After the first breath, the lungs fill with air instead of fluid
- PVR falls and Pulmonary BF increases
- Ductus initially protects the pulmonary vasculature from overload.
- Ductus Arteriosus starts to close via vasoconstriction immediately after birth
how long does its take for the Ductus Arteriosus to close? what might you see?
- Takes about 1-2 days to close in a full term infant
- Small shunt of blood from the Aorta to the left PA for a few days
what does the Ductus Arteriosus become
Ligamentum Arteriosum
how long does complete obliteration of the lumen of the Ductus Arteriosus take
1-3 months
ultimately, what becomes of the Umbilical Arteries
Medial Umbilical Ligaments
ultimately, what becomes of the Umbilical Vein
Ligamentum Teres (Round Ligament)
ultimately, what becomes of the Ductus Venosus
Ligamentum Venosum
ultimately, what becomes of the Foramen Ovale
Fossa Ovalis
ultimately, what becomes of the Ductus Arteriosus
Ligamentum Arteriosum
