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GIGU > Physiology of Pregnancy and the Fetus > Flashcards

Physiology of Pregnancy and the Fetus Flashcards

1
Q

What are the main fxns of the placenta?

A
  • supply nutrients
  • exchange O2 and CO2
  • regulates fluid volumes and disposal of wastes/metabolites
  • synthesizes steroids and proteins that affect maternal and fetal metabolism
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2
Q

What organs does the placenta take function over until birth?

A

lungs
kidney
gut
endocrine

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3
Q

What about the placenta is organized to facilitate exchange b/t mother and fetal circulation?

A

-large surface area for exchange

  • highly developed vasculature in maternal and fetal components
  • –>physically separate
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4
Q

What are the 3 main features of the placenta?

A

chorionic villi

intervillous space

decidua basalis

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5
Q

What is the functional unit of the placenta?

A

chorionic villi

–>extensive branching for increased surface area for exchange

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6
Q

What arteries empty from the mother into the intervillous space?

A

spiral arteries from maternal side, drained by maternal veins

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7
Q

Describe maternal blood flow in the placenta

A

Spiral A discharge in spurts into intervillous space

Filling dissipates force and velocity–>allows time for adequate exchange to villi

Blood drains through venous orifices, etners placental vein–>maternal veins

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8
Q

Are there capillaries in the maternal blood flow of the placenta?

A

NO

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9
Q

What do the 2 umbilical arteries carry?

A

deoxygenated blood

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10
Q

Where does fetal blood flow originate?

A

umbilical As

–>branch, penetrate chorionic plate to form chorionic villi capillary network

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11
Q

How does the umbilical vein receive oxygenated blood?

A

umbilical As from the fetus branch to the capillary network in the villi–> exchange with blood flowing from spiral As of mother–> taken up in single umbilical vein that is carried back to the fetus

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12
Q

What are the functions of the terminal dilations in the capillary network of villi?

A

has slower blood flow so it can exchange nutrients efficiently

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13
Q

Explain the PO2 change as oxygen flows from maternal blood–> intervillous space–> umbilical vein.

A

PO2 100mmHg in mother

Drops to 30-35 mmHg as it diffuses into villi

Drops further as it flows to umbilical vein

Fetal Hb able to get sufficient O2 saturation

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14
Q

Why is fetal Hb able to pick up more O2 c/t maternal Hb?

A

The PO2 is very low once it diffuses to the fetus, so needs to be able to pick up O2 efficiently

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15
Q

What factors cause CO2 to be transferred from the fetus to the mother?

A

Fetal blood has lower affinity for CO2 c/t mother

–>PCO2 is around 48 in umbilical As

–> PCO2 is around 43 in intervillous space

**CO2 flows down concentration gradient to mother

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16
Q

What are examples of passive exchange in the placenta?

A
  • non-protein nitrogen wastes (urea, creatine) from fetus to mother
  • lipid soluble hormones transfer between mother, placenta and fetus
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17
Q

What is an example of facilitated diffusion in the placenta?

A

glucose to fetus

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18
Q

What are examples of primary and secondary active transport to the fetus?

A

amino acids
vitamins
minerals

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19
Q

What are examples of receptor mediated endocytosis in the placenta?

A

Large molecule exchange

–> LDL, hormones (insulin), antibodies (IgG)

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20
Q

Describe the endocrine functions of the placenta

A
  • Manufactures hormones
  • —–>steroid, amines, polypeptides
  • Regulates via paracrine
  • –> releases local placental hormones into fetal or maternal circulations
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21
Q

What are the general functions of placental hormones in pregnancy?

A
  • maintain pregnant state of uterus
  • stimulate lobuloalveolar growth and function of maternal breasts
  • adapt maternal metabolism and physio to support growing fetus
  • regulate fetal development
  • regulate timing and progression of childbirth
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22
Q

What produces hCG?

A

syncytiotrophoblasts

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23
Q

What binds with high affinity to LH receptors and rapidly accumulates in maternal circulation?

A

hCG

24
Q

What is the primary fxn of hCG?

A

stimulate LH receptors in corpus luteum

  • -> maintain high levels of corpus luteum progesterone
  • -> prevent lysis of corpus luteum
25
Q

What does the small amount of hCG that enters the fetus do?

A

stimulates Leydig cells to produce testosterone

26
Q

What is thought to be responsible for nausea and morning sickness in pregnancy?

A

hCG

27
Q

Describe serum levels of hCG

A

double daily up to 10 weeks

28
Q

What produces hCS?

A

syncytiotrophoblasts

29
Q

When is hCS detected?

A

day 10 syncytiotrophoblasts

3 weeks maternal serum

30
Q

What is hCS?

A

human chorionic somatomammotropin

31
Q

What is hCS structurally related to?

A

growth hormone and prolactin

–>type of human placental lactogen

32
Q

What is the fxn of hCS?

A

coordinates fuel economy of fetoplacental unit

–> converts glucose to FA and ketones

–> promote development of mammary glands

–> lipolytic actions help mother shift to FFA use for energy

33
Q

What can contribute to diabetogenicity of pregnancy?

A

hCS

–>antagonistic action to maternal insulin

34
Q

What hormone is required for implantation and early maintenance of pregnancy?

A

progesterone via corpus luteum

35
Q

What is window of receptivity?

A

increased adhesion proteins in endometrium

–> activated via progesterone

36
Q

What stimulates endometrial gland secretions for early nutrient transfer?

A

progesterone

37
Q

What hormone reduces uterine motility, inhibits uterine contractions and induces mammary growth?

A

progesterone

38
Q

Describe serum levels of progesterone during pregnancy

A

High levels throughout pregnancy

–> from 20 to 120 ng/mL

39
Q

Describe serum levels of hCS during pregnancy

A

steadily increases until birth

–> 2 to 10 ug/mL

40
Q

What are the functions of estrogen in pregnancy?

A
  • induces endometrial growth
  • induces progesterone receptor expression
  • induces LH surge prior to ovulation
  • increases uteroplacental blood flow
  • increases LDL receptor expression in syncytiotrophoblasts
  • induces prostaglandins and oxytocin receptors for parturition
  • increases growth and development of mammary glands
41
Q

What are the concentrations of estrogen in serum during pregnancy?

A

Estradiol > estriol > estrone

42
Q

Describe the need for the maternal-placental-fetal unit

A

progesterone and estrogens increase way higher c/t nml menstrual cycle

placenta can’t produce them by itself

43
Q

Describe the maternal-placental-fetal unit

A

How it overcomes placental shortcomings:

  • Mother provides cholesterol
  • Fetal adrenal gland and liver supply enzymes that the placenta lacks
44
Q

When does the luteal-placental shift of progesterone occur?

A

week 8

–>placenta starts producing majority of progesterone

45
Q

Is progesterone production regulated in pregnancy?

A

NO

46
Q

How is progesterone formed in pregnancy?

A

Syncytiotrophoblasts import cholesterol from maternal blood

Express CYP11A1 and 3B-HSD1

  • -> released into maternal compartment
  • —–>causes consistent rise in maternal serum levels throughout pregnancy
47
Q

Can the placenta produce cholesterol?

A

NO- must get from mother

48
Q

How does MPF unit overcome placental shortcoming regarding estrogen production?

A

mother–> cholesterol

fetal adrenal gland and liver–> production of DHEAS and 16-OH DHEAS (weak androgens)

49
Q

Why can’t the placenta make estrogen by itself?

A
  • can’t make cholesterol
  • lacks 17a hydroxylase and 17, 20 desmolase
  • —> to make estrone and estradiol
  • lacks 16a hydroxylase
  • –>to make estriol
50
Q

When does preeclampsia occur?

A

after 20 weeks

5-8% of pregnancies

51
Q

What are the sx of preeclampsia?

A

HTN, signs of damage to kidney or other organ

—>proteinuria, generalized edema

52
Q

What is the cause of preeclampsia?

A

Unknown

–> existing maternal pathology, obesity, abnormal placentation, immunologic factors

53
Q

What can occur if preeclampsia is left untreated?

A

Eclampsia

Death (m and fetus)

HELLP
–> Hemolysis, Elevated Liver enzymes, Low Platelet count

54
Q

What happens to the fetus with preeclampsia?

A

limited blood supply to uterine arteries–> ischemia and endothelial damage

***release of cytokines

55
Q

Describe the placental of women with preeclampsia

A

abnormal, poor trophoblastic invasion

56
Q

Where is blood formed in the fetus?

A

yolk sac
liver
bone marrow

GIGU (37 decks)

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