Fetal Circulation and Physiology Flashcards Preview

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Flashcards in Fetal Circulation and Physiology Deck (60):
1

n the fetus, some organs do not function until birth

 Lungs
 Kidneys  GI Tract

2

Fetus obtains oxygen and nutrients

via diffusion from the maternal blood.

3

Wastes and CO2 are eliminated via

diffusion into the maternal blood

4

waste and oxygen exchange occurs via

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

5

Placenta

way of communication between mother and baby
 Site of exchange of nutrients/ wastes

6

Umbilical Artery

carries blood away from the fetus to
the placenta  Carries wastes and CO2  LOW O2 Content!

7

umbilical vein

carries blood from the placenta to the fetus
 Carries nutrients and O2  HIGH O2 Content

8

fetal capillaries

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

9

Intervillous Spaces

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

10

The placenta communicates with the mother’s cardiovascular
system via

uterine blood vessels.

11

waste from placenta

diffuse out of the capillaries into the intervillous spaces
containing maternal blood in the placenta.

12

Nutrients travel from mother’s blood vessels

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

13

The concentration of hemoglobin in fetal blood is about

50% higher
than maternal blood

14

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

30-35% more O2

15

THERE IS NO DIRECT MIXING

OF MATERNAL AND FETAL BLOOD!!!

16

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

17

The Placenta - Function Exchange Nutrients/ Electrolytes

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

18

Placental circulation has a very low

RESISTANCE

19

The Placenta - Function  Transfer of Maternal Antibodies

Late first trimester – fetus makes components of complement
Start of immunological competence

20

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.

21

The Placenta - Function
 Hormone Production

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

22

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

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

23

Oxygenated blood returns from the placenta via ______ with a sat_______

1 umbilical vein with a sat of 80%

24

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

25

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%

26

Fetal Lungs
 Filled with

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

27

Most fetal blood does not go from

the RV to the lungs

28

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.

29

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

30

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

31

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

32

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

33

The only fetal vessel to carry fully oxygenated blood is the

umbilical vein

34

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.

35

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

 Ductus Arteriosus  Foramen Ovale  Ductus Venosus

36

At birth, the _________ start to function.

Pulmonary, Renal and Digestive Systems

37

Neonatal Circulation
 Umbilical Arteries  Contraction of

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

38

Neonatal Circulation
 Umbilical Arteries functionally

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

39

umbilical arteries distal portion after birth will become

fibrous cords  Medial umbilical ligaments

40

umbilical arteries fully close

2-3 months after birth

41

Umbilical Vein
 Collapses shortly after

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

42

umbilical vein Remains as the

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

43

Neonatal Circulation
 Ductus Venosus

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

44

Patent Ductus Venosus is

extremely rare  Less than 20 reported world wide

45

Foramen Ovale
 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.

46

First breath presses

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

47

First days of life, closure

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

48

Constant apposition leads to

fusion of the septa

49

Anatomical (permanent) closure o septa occurs within

one year

50

After a year, if the Foramen Ovale has not closed

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

51

prevalence of PFO

27%. patients are usually asymptomatic

52

Ductus Arteriosus
 Closes via

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

53

ductus arteriosis closes in

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

54

small shunt of blood from aorta to PA becomes

Ligamentum Arteriosum

55

omplete obliteration of the lumen

takes 1-3 months.

56

Umbilical Arteries becomes

– Medial Umbilical Ligaments

57

vein becomes

Ligamentum Teres (Round Ligament

58

ductus venosus becomes

Ligamentum Venosum

59

foramen ovale becomes

Fossa Ovalis

60

Ductus Arteriosus becomes

Ligamentum Arteriosum