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Pediatrics > Fetal Circulation and Physiology > Flashcards

Fetal Circulation and Physiology Flashcards

1
Q

n the fetus, some organs do not function until birth

A

 Lungs

 Kidneys  GI Tract

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2
Q

Fetus obtains oxygen and nutrients

A

via diffusion from the maternal blood.

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3
Q

Wastes and CO2 are eliminated via

A

diffusion into the maternal blood

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4
Q

waste and oxygen exchange occurs via

A

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

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5
Q

Placenta

A

way of communication between mother and baby

 Site of exchange of nutrients/ wastes

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6
Q

Umbilical Artery

A

carries blood away from the fetus to

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

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7
Q

umbilical vein

A

carries blood from the placenta to the fetus

 Carries nutrients and O2  HIGH O2 Content

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8
Q

fetal capillaries

A

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

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9
Q

Intervillous Spaces

A

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

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10
Q

The placenta communicates with the mother’s cardiovascular

system via

A

uterine blood vessels.

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11
Q

waste from placenta

A

diffuse out of the capillaries into the intervillous spaces

containing maternal blood in the placenta.

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12
Q

Nutrients travel from mother’s blood vessels

A

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

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13
Q

The concentration of hemoglobin in fetal blood is about

A

50% higher

than maternal blood

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14
Q

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

A

30-35% more O2

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15
Q

THERE IS NO DIRECT MIXING

A

OF MATERNAL AND FETAL BLOOD!!!

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16
Q

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

A

 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

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17
Q

The Placenta - Function Exchange Nutrients/ Electrolytes

A

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

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18
Q

Placental circulation has a very low

A

RESISTANCE

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19
Q

The Placenta - Function  Transfer of Maternal Antibodies

A

Late first trimester – fetus makes components of complement

Start of immunological competence

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20
Q

The Placenta - Function mmunoglobulins – Primarily IgG

A

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.

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21
Q

The Placenta - Function

 Hormone Production

A

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

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22
Q

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

A

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

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23
Q

Oxygenated blood returns from the placenta via ______ with a sat_______

A

1 umbilical vein with a sat of 80%

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24
Q

oxygenated blood goes to the liver where it branches into

A

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

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25
Q

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

A

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

26
Q

Fetal Lungs

 Filled with

A

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

27
Q

Most fetal blood does not go from

A

the RV to the lungs

28
Q

Most fetal blood passes through

A

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
Q

In the LA, blood mixes

A

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
Q

Fetal blood returning to the heart from the SVC

A

bypasses the Foramen Ovale and enters the RA

 Goes to the RV and pumped to the PA

31
Q

Pulmonary Vascular Resistance is so high that

A

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
Q

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

A

low through the internal iliacs to the umbilical artery

 Will go to the placenta for nutrient/waste exchange

33
Q

The only fetal vessel to carry fully oxygenated blood is the

A

umbilical vein

34
Q

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

A

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

35
Q

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

A

 Ductus Arteriosus  Foramen Ovale  Ductus Venosus

36
Q

At birth, the _________ start to function.

A

Pulmonary, Renal and Digestive Systems

37
Q

Neonatal Circulation

 Umbilical Arteries  Contraction of

A

smooth muscle in walls

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

38
Q

Neonatal Circulation

 Umbilical Arteries functionally

A

close a few minutes after birth

 Eventually will fill with connective tissue

39
Q

umbilical arteries distal portion after birth will become

A

fibrous cords  Medial umbilical ligaments

40
Q

umbilical arteries fully close

A

2-3 months after birth

41
Q

Umbilical Vein

 Collapses shortly after

A

the umbilical arteries

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

42
Q

umbilical vein Remains as the

A

as the ligamentum teres hepatis

 Lower margin of the falciform ligament. Attaches the umbilicus to the liver

43
Q

Neonatal Circulation

 Ductus Venosus

A

Collapses

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

44
Q

Patent Ductus Venosus is

A

extremely rare  Less than 20 reported world wide

45
Q

Foramen Ovale

 Usually______ due to

A

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
Q

First breath presses

A

the septum primum against the septum secundum

 causes functional closure of the foramen ovale at birth.

47
Q

First days of life, closure

A

is reversible

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

48
Q

Constant apposition leads to

A

fusion of the septa

49
Q

Anatomical (permanent) closure o septa occurs within

A

one year

50
Q

After a year, if the Foramen Ovale has not closed

A

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

51
Q

prevalence of PFO

A

27%. patients are usually asymptomatic

52
Q

Ductus Arteriosus

 Closes via

A

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

53
Q

ductus arteriosis closes in

A

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

54
Q

small shunt of blood from aorta to PA becomes

A

Ligamentum Arteriosum

55
Q

omplete obliteration of the lumen

A

takes 1-3 months.

56
Q

Umbilical Arteries becomes

A

– Medial Umbilical Ligaments

57
Q

vein becomes

A

Ligamentum Teres (Round Ligament

58
Q

ductus venosus becomes

A

Ligamentum Venosum

59
Q

foramen ovale becomes

A

Fossa Ovalis

60
Q

Ductus Arteriosus becomes

A

Ligamentum Arteriosum

Pediatrics (14 decks)

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