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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?

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
What does the small amount of hCG that enters the fetus do?
stimulates Leydig cells to produce testosterone
26
What is thought to be responsible for nausea and morning sickness in pregnancy?
hCG
27
Describe serum levels of hCG
double daily up to 10 weeks
28
What produces hCS?
syncytiotrophoblasts
29
When is hCS detected?
day 10 syncytiotrophoblasts 3 weeks maternal serum
30
What is hCS?
human chorionic somatomammotropin
31
What is hCS structurally related to?
growth hormone and prolactin -->type of human placental lactogen
32
What is the fxn of hCS?
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
What can contribute to diabetogenicity of pregnancy?
hCS -->antagonistic action to maternal insulin
34
What hormone is required for implantation and early maintenance of pregnancy?
progesterone via corpus luteum
35
What is window of receptivity?
increased adhesion proteins in endometrium --> activated via progesterone
36
What stimulates endometrial gland secretions for early nutrient transfer?
progesterone
37
What hormone reduces uterine motility, inhibits uterine contractions and induces mammary growth?
progesterone
38
Describe serum levels of progesterone during pregnancy
High levels throughout pregnancy | --> from 20 to 120 ng/mL
39
Describe serum levels of hCS during pregnancy
steadily increases until birth --> 2 to 10 ug/mL
40
What are the functions of estrogen in pregnancy?
- 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
What are the concentrations of estrogen in serum during pregnancy?
Estradiol > estriol > estrone
42
Describe the need for the maternal-placental-fetal unit
progesterone and estrogens increase way higher c/t nml menstrual cycle placenta can't produce them by itself
43
Describe the maternal-placental-fetal unit
How it overcomes placental shortcomings: - Mother provides cholesterol - Fetal adrenal gland and liver supply enzymes that the placenta lacks
44
When does the luteal-placental shift of progesterone occur?
week 8 -->placenta starts producing majority of progesterone
45
Is progesterone production regulated in pregnancy?
NO
46
How is progesterone formed in pregnancy?
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
Can the placenta produce cholesterol?
NO- must get from mother
48
How does MPF unit overcome placental shortcoming regarding estrogen production?
mother--> cholesterol fetal adrenal gland and liver--> production of DHEAS and 16-OH DHEAS (weak androgens)
49
Why can't the placenta make estrogen by itself?
- can't make cholesterol - lacks 17a hydroxylase and 17, 20 desmolase - ---> to make estrone and estradiol - lacks 16a hydroxylase - -->to make estriol
50
When does preeclampsia occur?
after 20 weeks 5-8% of pregnancies
51
What are the sx of preeclampsia?
HTN, signs of damage to kidney or other organ | --->proteinuria, generalized edema
52
What is the cause of preeclampsia?
Unknown --> existing maternal pathology, obesity, abnormal placentation, immunologic factors
53
What can occur if preeclampsia is left untreated?
Eclampsia Death (m and fetus) HELLP --> Hemolysis, Elevated Liver enzymes, Low Platelet count
54
What happens to the fetus with preeclampsia?
limited blood supply to uterine arteries--> ischemia and endothelial damage ***release of cytokines
55
Describe the placental of women with preeclampsia
abnormal, poor trophoblastic invasion
56
Where is blood formed in the fetus?
yolk sac liver bone marrow

GIGU (37 decks)

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