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GIGU Final > Physiology of Pregnancy and the Fetus > Flashcards

Physiology of Pregnancy and the Fetus Flashcards

1
Q

How does the placenta act like an endocrine gland?

A

it synthesizes steroids and proteins that affect both maternal and fetal metabolism

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2
Q

what are the three major features of the placenta?

A

the chorionic villi, the intervillous space, and the decidua basalis

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3
Q

what represent the functional unit of the placenta?

A

the chorionic villi

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4
Q

Why is the branching of the chorionic villi important?

A

it increases the surface area for exchange to happen

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5
Q

what empties into the intervillous space?

A

spiral arteries from the maternal side

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6
Q

why is it important to have a slowing of blood flow into the intervillous space?

A

it allows adequate time for exchange of nutrients

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7
Q

how does the fetal blood travel from the fetal circulation to the placenta?

A

via the umbilical arteries and into the chorionic villi (2)

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8
Q

what do the two umbilical arteries carry?

A

deoxygenated blood

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9
Q

How can the terminal umbilical arteries be described?

A

they have terminal dilations to slower blood flow and allow for exchange of nutrients

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10
Q

how does blood travel from the placenta back to the fetus?

A

via the single umbilical vein

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11
Q

diffusion of O2 into the chorionic villi has what affect on the Po2?

A

it causes the Po2 of blood in the intervillous space to fall to 30-35 mmHg and lower in the umbilical vein of the fetus

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12
Q

How does fetal hemoglobin and adult hemoglobin differ?

A

fetal hemoglobin has a much higher affinity for O2 than adult hemoglobin

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13
Q

what drives CO2 transfer?

A

concentration gradient differences

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14
Q

what is the Pco2 in the umbilical arteries near term? and in the intervillous space?

A

it is 48 mmHg in the umbilical arteries and 43mmHg in the intervillous space; all factors favor transfer of Co2 from fetus to mother

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15
Q

what things cross the placenta via passive exchange?

A

non-protein nitrogen wastes (urea/creatinine) from fetus to mother; lipid soluble hormones

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16
Q

how does glucose get from the mother to the fetus?

A

facilitated diffusion

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17
Q

what things get to the fetus via primary and secondary active transport to support growth?

A

amino acids, vitamins, and minerals

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18
Q

what things get from the mother to the fetus via receptor mediated endocytosis?

A

large molecule exchange- LDL, hormones like insulin, and antibodies (IgG)

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19
Q

how does the placenta regulate in a paracrine fashion?

A

it releases local placental hormones, it releases hormones into fetal or maternal circulations

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20
Q

what effect do the placental hormones have on the breasts?

A

they stimulate lobuloalveolar growth and function of maternal breasts

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21
Q

what is hCG produced by?

A

syncytiotrophoblasts

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22
Q

what does hCG bind with high affinity to?

A

LH receptors (it is structurally related to LH)

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23
Q

what is the primary function of hCG?

A

to stimulate LH receptors in the corpus luteum

24
Q

what happens when hCG stimulates LH receptors in the corpus luteum?

A

it prevents luteolysis and it maintains high levels of luteal-derived progesterone

25
Q

what effect does the small amount of hCG that enter fetal circulation have on the fetus?

A

it stimulates fetal leydig cells to produce testosterone

26
Q

why does hCG have a much longer half life than LH?

A

due to glycosylation (the longer half life allows it to quickly accumulate in maternal circulation

27
Q

what hormone does the placenta secrete that is structurally related to growth hormone and prolactin?

A

hPL (aka hCS)

28
Q

what part of the placenta produces the hPL aka hCS?

A

the syncytiotrophoblast

29
Q

what effect does hPL aka hCS have on mother?

A

causes maternal blood glucose levels to increase (there is an inhibition of peripheral glucose uptake in the mother), but it helps contribute to the nutrition of the fetus

30
Q

what effect does hPL have on the mother’s insulin levels?

A

she will have a resistance to endogenous insulin

31
Q

when does the placenta take over progesterone secretion from the corpus luteum?

A

about the 8th week of pregnancy

32
Q

why is progesterone needed all throughout pregnancy, not just for the initial implantation?

A

it reduces uterine motility, inhibits propagation of uterine contractions. (by inhibiting the oxytocin receptor), induces mammary growth and differentiation

33
Q

what effect does estrogen secreted from the placenta have on pregnancy?

A

it increases uteroplacental blood flow, increases LDL receptor expression in syncytiotrophoblasts, induces prostaglandins and oxytocin receptors necessary for parturition

34
Q

How does the mother contribute to the high maternal levels of progesterones and estrogens?

A

the mother supplies cholesterol (used as a precursor to steroid hormone production)

35
Q

How does the fetus contribute to high maternal levels of progesterone and estrogens?

A

the fetal adrenal gland and liver supply enzymes the placenta lacks for the conversion of intermediate products in steroid hormone synthesis

36
Q

how is progesterone production regulated?

A

it is largely unregulated

37
Q

how does the placenta produce progesterone?

A

the syncytiotrophoblasts import cholesterol from the maternal blood, and they will use CYP11A1 and 3beta-HSD1 to convert it into progesterone and then release it back into the maternal blood

38
Q

how does the placenta produce estrogen if it doesn’t have cholesterol or 17-alpha hydroxylase, 17,20 desmolase, or 16-alpha hydroxylase?

A

the fetal adrenal gland and liver supply the enzymes needed; the mother supplies the cholesterol

39
Q

the fetal circulatory system uses 3 shunts, what are they?

A

ductus venosis, foramen ovale, and ductus arteriosis

40
Q

what is the ductus venosis for?

A

to bypass the fetal liver (not fully functional until late pregnancy/just after birth)

41
Q

what is the foramen ovale used for?

A

it moves blood from the right atrium to the left atrium

42
Q

what is the ductus arteriosis used for?

A

it moves blood from the pulmonary artery to the aorta

43
Q

what does the ductus venosus provide?

A

a direct route from the placenta to the inferior vena cava and then to the right atrium

44
Q

what is the foramen ovale and where is it?

A

it is a hole in the septum dividing the right and left atria- it is on the posterior aspect of the right atrium

45
Q

what does the foramen ovale allow bypass of?

A

the right ventricle

46
Q

what does the ductus arteriosus allow bypass of?

A

the lungs

47
Q

which duct closes rapidly- within taking the first few breaths of air?

A

the ductus arteriosus

48
Q

what causes the ductus arteriosus to close?

A

there is a major reduction in pulmonary pressure and an increase in aortic pressure

49
Q

what is a clinical finding of a patent ductus arteriosis (PDA)?

A

it can be heard as a heart murmur

50
Q

what can result from patent ductus arteriosus?

A

it puts a strain on the heart and it increases the pulmonary blood pressure

51
Q

what causes the foramen ovale to close?

A

this closure results from changes in pressure across the atrium; there is increased venous return to the left atrium and elevated left arterial pressure

52
Q

what does closure of the foramen ovale establish?

A

left and right circulatory system

53
Q

what causes a patent foramen ovale?

A

increased right atrial pressure can push the flap open

54
Q

what is the effect of a patent foramen ovale?

A

sustained pulmonary hypertension or transient increases

55
Q

what causes the ductus venosus to close?

A

within 1-3 hours after birth, the muscle wall of the ductus venosus contracts and closes due to decreased blood flow and pressure changes; the portal venous pressure rises, which forces venous blood through liver sinuses

GIGU Final (15 decks)

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