Fetal Circulation and Physiology

Question 1

n the fetus, some organs do not function until birth

Answer 1

 Lungs

 Kidneys  GI Tract

Question 2

Fetus obtains oxygen and nutrients

Answer 2

via diffusion from the maternal blood.

Question 3

Wastes and CO2 are eliminated via

Answer 3

diffusion into the maternal blood

Question 4

waste and oxygen exchange occurs via

Answer 4

the placenta  Inside the uterus  Attached to baby via the umbilical cord

Question 5

Placenta

Answer 5

way of communication between mother and baby

 Site of exchange of nutrients/ wastes

Question 6

Umbilical Artery

Answer 6

carries blood away from the fetus to

the placenta  Carries wastes and CO2  LOW O2 Content!

Question 7

umbilical vein

Answer 7

carries blood from the placenta to the fetus

 Carries nutrients and O2  HIGH O2 Content

Question 8

fetal capillaries

Answer 8

Umbilical arteries and veins branch into these capillaries located inside the intervillous spaces in the placenta.

Question 9

Intervillous Spaces

Answer 9

Spaces filled with maternal blood from uterine arterioles. Drained by Uterine veins.

Question 10

The placenta communicates with the mother’s cardiovascular

system via

Answer 10

uterine blood vessels.

Question 11

waste from placenta

Answer 11

diffuse out of the capillaries into the intervillous spaces

containing maternal blood in the placenta.

Question 12

Nutrients travel from mother’s blood vessels

Answer 12

to the intervillous space via uterine arteries.  Diffuse from the intervillous spaces into the fetal capillaries

Question 13

The concentration of hemoglobin in fetal blood is about

Answer 13

50% higher

than maternal blood

Question 14

Fetal hemoglobin has a greater affinity for oxygen than maternal blood
 Can carry

Answer 14

30-35% more O2

Question 15

THERE IS NO DIRECT MIXING

Answer 15

OF MATERNAL AND FETAL BLOOD!!!

Question 16

The Placenta - Function  Exchange of gases – CO2, O2, CO

Answer 16

 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

Question 17

The Placenta - Function Exchange Nutrients/ Electrolytes

Answer 17

 Amino Acids, Free Fatty Acids, Carbohydrates, Vitamins  Exchange is rapid and increases as pregnancy increases

Question 18

Placental circulation has a very low

Answer 18

RESISTANCE

Question 19

The Placenta - Function  Transfer of Maternal Antibodies

Answer 19

Late first trimester – fetus makes components of complement

Start of immunological competence

Question 20

The Placenta - Function mmunoglobulins – Primarily IgG

Answer 20

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.

Question 21

The Placenta - Function

 Hormone Production

Answer 21

 4th month – placenta produces enough progesterone
to support pregnancy, should corpus luteum fails
 Continues to produce estrogenic hormones  Estriol
Rises until end of pregnancy

Question 22

Umbilical Blood Vessels  Blood passes from the fetus to the placenta via________ THAT BRANCH OFF______ WITH a sat. of______

Answer 22

2 umbilical
arteries
 Branch of the internal iliac arteries  Sat ~58%

Question 23

Oxygenated blood returns from the placenta via ______ with a sat_______

Answer 23

1 umbilical vein with a sat of 80%

Question 24

oxygenated blood goes to the liver where it branches into

Answer 24

Joins hepatic portal vein -> Liver (1/3)
 Ductus Venosus -> IVC (2/3)
 Sphincter mechanism in ductus that controls blood flow through the liver

Question 25

n the IVC, oxygenated blood via the______ and sat falls to

Answer 25

ductus venosus meets deoxygenated blood from the lower body. Sat falls to about 67%

Question 26

Fetal Lungs |  Filled with

Answer 26

fetal lung fluid. Not used to oxygenate blood. This liquid increases the pulmonary vascular resistance to blood flow

Question 27

Most fetal blood does not go from

Answer 27

the RV to the lungs

Question 28

Most fetal blood passes through

Answer 28

Foramen Ovale  Hole between the Right and Left Atria. Blood entering from the IVC is guided toward the foramen ovale to the Left Atrium.

Question 29

In the LA, blood mixes

Answer 29

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

Question 30

Fetal blood returning to the heart from the SVC

Answer 30

bypasses the Foramen Ovale and enters the RA |  Goes to the RV and pumped to the PA

Question 31

Pulmonary Vascular Resistance is so high that

Answer 31

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

Question 32

At the common iliac branch to the internal and external iliacs  Part of that blood flowing systemically will

Answer 32

low through the internal iliacs to the umbilical artery |  Will go to the placenta for nutrient/waste exchange

Question 33

The only fetal vessel to carry fully oxygenated blood is the

Answer 33

umbilical vein

Question 34

Blood entering the aorta from the LV and perfusing the head and heart has

Answer 34

a higher oxygen content than the blood perfusing the rest of the body.

Question 35

There are 3 shunts present in the fetal circulation that normally close after birth:

Answer 35

 Ductus Arteriosus  Foramen Ovale  Ductus Venosus

Question 36

At birth, the _________ start to function.

Answer 36

Pulmonary, Renal and Digestive Systems

Question 37

Neonatal Circulation |  Umbilical Arteries  Contraction of

Answer 37

smooth muscle in walls |  Likely caused by thermal and mechanical stimuli and change in oxygen tension

Question 38

Neonatal Circulation |  Umbilical Arteries functionally

Answer 38

close a few minutes after birth |  Eventually will fill with connective tissue

Question 39

umbilical arteries distal portion after birth will become

Answer 39

fibrous cords  Medial umbilical ligaments

Question 40

umbilical arteries fully close

Answer 40

2-3 months after birth

Question 41

Umbilical Vein |  Collapses shortly after

Answer 41

the umbilical arteries |  Blood from the placenta may enter newborn for some time after birth.

Question 42

umbilical vein Remains as the

Answer 42

as the ligamentum teres hepatis |  Lower margin of the falciform ligament. Attaches the umbilicus to the liver

Question 43

Neonatal Circulation |  Ductus Venosus

Answer 43

Collapses |  Remains as Ligamentum Venosum  Fibrous cord on the inferior surface of the liver

Question 44

Patent Ductus Venosus is

Answer 44

extremely rare  Less than 20 reported world wide

Question 45

Foramen Ovale |  Usually______ due to

Answer 45

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.

Question 46

First breath presses

Answer 46

the septum primum against the septum secundum |  causes functional closure of the foramen ovale at birth.

Question 47

First days of life, closure

Answer 47

is reversible |  Crying by baby creates a right to left shunt and can account for the cyanotic periods of newborns.

Question 48

Constant apposition leads to

Answer 48

fusion of the septa

Question 49

Anatomical (permanent) closure o septa occurs within

Answer 49

one year

Question 50

After a year, if the Foramen Ovale has not closed

Answer 50

it is referred to as a Patent Foramen Ovale (PFO).

Question 51

prevalence of PFO

Answer 51

27%. patients are usually asymptomatic

Question 52

Ductus Arteriosus |  Closes via

Answer 52

ontraction of the muscular wall immediately after birth.  Mediated by Bradykinin which is released by the lungs during the initial inflation.

Question 53

ductus arteriosis closes in

Answer 53

1-2 days. small shunt of blood from the Aorta to the left PA for a few days

Question 54

small shunt of blood from aorta to PA becomes

Answer 54

Ligamentum Arteriosum

Question 55

omplete obliteration of the lumen

Answer 55

takes 1-3 months.

Question 56

Umbilical Arteries becomes

Answer 56

– Medial Umbilical Ligaments

Question 57

vein becomes

Answer 57

Ligamentum Teres (Round Ligament

Question 58

ductus venosus becomes

Answer 58

Ligamentum Venosum

Question 59

foramen ovale becomes

Answer 59

Fossa Ovalis

Question 60

Ductus Arteriosus becomes

Answer 60

Ligamentum Arteriosum