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ENRE > Physiology of Pregnancy, Parturition, and Lactation > Flashcards

Physiology of Pregnancy, Parturition, and Lactation Flashcards

1
Q

What is the functional unit of the placenta?

A

chorionic villus

*extensive branching increases SA for maternal-fetal exchange

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2
Q

Where do spiral arteries empty?

A

directly into the intervillous space

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3
Q

How does maternal blood flow to and from baby?

A

enters in pulses to wall of uterus –> inter-villous space –> bathes chorionic villi –> drains through venous orifices in basal plate –> enters maternal placental veins –> into pelvic Vs

*intervillous space is functional capillary bed

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4
Q

How do uterine contractions affect maternal blood flow?

A

attenuate arterial inflow and completely interrupt venous drainage –> volume of blood in IVS increases so there is continual exchange

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5
Q

What are 2 important functions of the amniotic fluid in relation to blood flow?

A

mechanical buffer to protect fetus from external damage

excretes waste products through it

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6
Q

How does the Pressure of O2 change across the placenta?

A

maternal blood coming into IVS has arterial blood gas = PO2 of 100 mmHg

diffusion into chorionic villi causes PO2 of blood in IVS to fall = 30-35 mmHg

PO2 of blood in umbilical V is even less

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7
Q

How does the fetus overcome the low PO2 in the IVS?

A

fetal Hb has much higher affinity for O2 than maternal Hb

fetus has relatively high CO per unit body weight –> increases O2 carrying capacity of fetal blood –> Hb rises to 50% higher in fetus

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8
Q

What things move across the placenta passively?

A

waste products

lipid-soluble steroid hormones

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9
Q

How does glucose move across the placenta?

A

facilitated diffusion

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10
Q

What things move across the placenta via active transport?

A

amino acids

vitamins and minerals

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11
Q

What molecules move across the placenta via receptor-mediated endocytosis?

A

LDL

transferrin

some hormones and Abs

*uptake of these increases throughout gestation until just before birth

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12
Q

What part of the placenta produces hormones?

A

syncytiotrophoblasts

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13
Q

What is hCG secretion like throughout pregnancy?

A

first hormone produced by syncytiotrophoblasts

rapidly accumulates in maternal circulation, detectable w/in 24 hrs of implantation

doubles every 2 days for 1st 6 weeks –> peak at 10 weeks, then declines to constant level

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14
Q

What is the action of hCG?

A

binds w/ high affinity to LH receptor –> stimulates corpus luteum to keep making progesterone in first 10 weeks

causes nausea of morning sickness

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15
Q

What is human placental lactogen (hPL) secretion like throughout pregnancy?

A

1st made 10 days after conception –> in maternal serum by 3 weeks

rise progressively throughout remainder of pregnancy

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16
Q

What are the actions of hPL?

A

structurally similar to GH and prolactin

antagonistic to insulin –> diabetogenicity

inhibits maternal glucose uptake –> more for baby

helps mother shift to use of FFAs for energy

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17
Q

What is placental progesterone secretion like throughout pregnancy?

A

production is largely unregulated - produces as much as the supply of cholesterol, desmolase, and 3beta-HSD will allow

levels increase throughout pregnancy

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18
Q

What is estriol production dependent on?

A

a healthy fetus

levels can be used to assess fetal well-being

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19
Q

What are the functions of estrogens in pregnancy?

A

increase uteroplacental blood flow

enhance LDL receptor expression in syncytiotrophoblasts

induce prostaglandin and oxytocin receptors

increase growth and development of mammary glands

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20
Q

What major hormone can the fenal adrenal cortex synthesize and how is it dealt with?

A

cortisol –> may be fetal signal for contractions, other things late in pregnancy

11B-HSD converts it to cortisone in syncytiotrophoblasts = weaker, so not too much floating around

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21
Q

On what day of the menstrual cycle does implantation usually occur?

A

~ day 21

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22
Q

What are the major functions of progesterone in early pregnancy?

A

stimulates secretion from uterine glands –> provides nutrients to embryo = histotrophic nutrition

inhibits myometrial contraction and release of paracrine factors that lead to menstruation

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23
Q

What does progesterone due in the indow of receptivity?

A

increases adhesivity of endo epithelium

formation of cellular extensions on apical surface of epithelia

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24
Q

What is important about the extensive blood supply in the endometrium during receptive window/implantation?

A

critical role in capturing embryonic hCG and taking it to ovary to maintain pregnancy

also allows for good delivery of progesterone back to endo

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25
Q

When does the source of progesterone and estrogens in pregnancy switch?

A

8 weeks

from corpus luteum –> placenta

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26
Q

What 3 enzymes are in the placenta and not in the fetus, and what do they do?

A

sulfatase: converts DHEA-S –> DHEA

aromatase and 3beta-HSD: involved in converting DHEA –> Estradiol

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27
Q

What 3 enzymes are in the fetus, but not in the placenta and what do they do?

A

17 alpha-hydroxylase/17,20 desmolase: progesterone –> 17alpha-hydroxyprogesterone

16alpha-hydroxylase: in fetal liver; DHEA-S –> 16alpha-OH DHEA-S

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28
Q

What does the mother do to help the placenta create hormones?

How does the fetus help?

A

mother: supplies it with LDL = cholesterol
fetus: supplies placenta w/ lacking enzymes

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29
Q

What hormone should the fetus NOT create?

A

estrogens - if so, fetus would be exposed to dangerous levels of E

*can’t make E bc no 3B-HSD and aromatase

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30
Q

How does the fetus reduce the activity of steroid intermediates?

A

sulfates them

does this to pregnenolone, DHEA, and 16A-OH-DHEA

(sulfate removed in placenta)

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31
Q

What occurs to maternal blood volume during pregnancy and how?

A

blood volume increases - starts during 1st trimester, grows rapidly in second, evens out in 3rd

mediated by increases in aldosterone

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32
Q

What occurs to mean arterial pressure of the mom during pregnancy?

A

increased plasma volume, but decreased peripheral vascular resistance –> MAP usually decreases during mid-pregnancy, then rises in 3rd trimester

33
Q

What occurs to maternal cardiac output in pregnancy?

A

increases a lot in 1st trimester (35-40%) –> only slight increase during 2nd and 3rd

reflects increase in stroke volume and HR

34
Q

How does progesterone affect maternal lungs?

A

increase alveolar ventilation via increased tidal volume

35
Q

What are the main maternal GI tract changes in pregnancy?

A

morning sickness resolved by 14-16 wks

prolonged gastric empty time

decreased GE sphincter toen –> acid reflux

decreased colon motility –> constipation

36
Q

What is the obstetric definition of labor?

A

series of regular, rhythmic, and forceful contractions that develops to facilitate thinning and dilation of cervix

37
Q

What are the stages of labor?

A

0 = tranquility

1 = uterine awakening, initiation of parturition, extending to complete cervical dilation

2 = active labor, from complete dilation to delivery

3 = from delivery to expulsion of placenta and final contraction

38
Q

What physiological change occurs in the uterus during labor?

A

increased number of gap jxns btw myometrial cells

increase in oxytocin receptors

39
Q

What is fetal station?

A

where the baby is in the pelvis

presenting part = part leading way through canal

0 station = when head is even w/ ischial spines

  • numbers = superior to spines

+ numbers = inferior to spines

40
Q

What does estrogen do to induce labor?

A

increases degree of uterine contractility

stimulates synthesis of oxytocin receptors

41
Q

What do prostaglandins do to induce labor?

A

initiate labor

uterine stretch, estrogen, and oxytocin induce synthesis

PGF 2a and PGE 2 –> increase uterine motility

levels increase in uterus, placenta, amniotic fluid, and fetal membranes before onset of labor

42
Q

What occurs to the uterus’s sensitivity to oxytocin close to labor?

A

insensitive to oxytocin until 20 weeks –> receptors increase 80x –> baseline at 36 weeks –> rises 200x during early labor

*uterus only susceptible to oxytocin at end of pregnancy vs prostaglandins throughout pregnancy

43
Q

What hormone is thought to initiate rhythmic uterine contractions?

A

prostaglandins

(increased oxytocin does NOT do this)

44
Q

What does oxytocin bind to stimulate prostaglandins?

A

receptors on decidual cells –> prostaglandins

*because it can stim prostaglandins, oxytocin may play role in expulsion of fetus during 2nd stage of labor

45
Q

What 2 things stimulate oxytocin response?

A

estrogen –> more oxytocin receptors

cervix stretch –> increased oxytocin release

46
Q

What does OT do after fetus is expelled?

A

causes uterus to contract immediately after birth –> limits blood flow and blood loss

basal maternal OT levels unchanged after delivery

fetal OT higher after vaginal delivery than C section

47
Q

What is relaxin?

A

produced by corpus luteum, placenta, and decidua

keeps uterus quiescent during pregnancy

production and release increases during labor

may soften and dilate cervix during labor

48
Q

How do the fetal pituitary, adrenals, and placental membrane affect the uterus during labor?

A

pit: oxytocin
adrenals: cortisol –> may be uterine stimulant

placental membranes –> prostaglandins –> increase intensity of contractions

49
Q

What is significant about fetal movements and labor?

A

fetal movements –> stretch uterus –> increases its contractility

twins are born on avg 19 days earlier than single child

50
Q

What are Braxton Hicks contractions?

A

weak and slow rhythmic contractions that occur throughout pregnancy

51
Q

How are labor contractions mediated?

A

by positive feedback:

stretch –> oxytocin and prostaglandins –> contraction –> stretch

loop that keeps going

52
Q

What is effacement?

A

cervix prepares for delivery

becomes soft, short, and thinner

100% effaced = paper-thin, labor about to occur

53
Q

Describe descent and expulsion.

A

cervix fully dilated: 10 cm

contractions strongest at top pushing fetus down

avg 20-50 min in duration

54
Q

What is considered prolonged labor?

A

lasting more than 18-24 hrs

2 types: early labor > 8hrs or active phase is > 12 hrs

55
Q

What is the other word for obstructed labor?

A

labor dystocia

56
Q

What is considered preterm labor?

A

before 37th week

12% of all pregnancies

uterine contractions cause cervix to open earlier than normal

risk factors: uti, uterin/cervical abnormalities, chronic illness, smoking drinking, EtOH, etc.

57
Q

What are risk factors for a ruptured uterus?

A

uterine scar from previous C section

dysfunctional/prolonged labor

labor augmentation by OT or PG

excessive manual pressure applied by fundus during delivery

58
Q

What are the leading and cardinal signs of a ruptured uterus?

A

leading = deterioration of fetal heart rate

cardinal = loss of fetal station on manual vaginal exam

59
Q

What is preeclampsia?

A

high blood pressure and signs of damage to another organ sys, often kidneys

proteinuria and generalized edema seen

occurs after week 20 of pregnancy

5-8% of pregnancies

60
Q

What is a proposed cause of preeclampsia?

A

disease of placenta:

associated w/ limited blood supply to uterine As –> ischemia and endothelial damage w/ release of cytokines

placenta of women w/ preE has poor trophoblastic invasion

61
Q

What endothelial things are thought to be changed during preeclampsia?

A

increased: ET-1, TBx, ANGII (due to autoAb)
decreased: NO, PG2

62
Q

What is the general organization of the breast?

A

alveoli –> lobule –> drains to ductule –> widens into ampulla

63
Q

What makes up a lactation alveolus?

A

secretory epithelial cells (alveolar cells)

contractile myoepithelial cells

surrounded by adipose tissue

64
Q

What does breast development at puberty and pregnancy depend on?

A

puberty: estrogens and progesterone
pregnancy: PRL and hPL and very high E and P –> full development

65
Q

What are mammogenic hormones?

A

promote proliferation of alveolar and duct cells

Estrogen

GH

Cortisol

Prolactin

Relaxin?

66
Q

What are lactogenic hormones?

A

promote initiation of milk production by alvelar cells

Prolactin

hCS

Cortisol

Insulin

Thyroid Hormones

withdrawal of E and P

67
Q

What are galactokinetic hormones?

A

promote contraction of myoepithelial cells and thus milk ejection

Oxytocin

Vasopressin

68
Q

What are galactopoietic hormones?

A

maintain milk production after it has been established

prolactin (primary)

cortisol and others

69
Q

What are the 5 main routes of milk secretion?

A
  1. secretory path
  2. transcellular endocytosis/exocytosis
  3. lipid path
  4. trancellular salt and water transport
  5. paracellular path
70
Q

What is the secretory pathway of milk secretion?

A

milk proteins lactalbumin and casein synth in ER –> golgi

alveolar cells add Ca and Pi to golgi

lactose synthesized

water enters secretory vesicles by osmosis

exocytosis

71
Q

What is the transcellular endocytosis/exocytosis path of milk secretion?

A

maternal immunoglobulins (IgA) taken up by endocytosis on basolateral side

secreted via exocytosis –> absorbed in baby’s GI

72
Q

What is the lipid pathway of milk secretion?

A

FAs form lipid droplets in alvelar cells –> secreted in membrane-bound sacs

73
Q

What is the transcellular salt and water path of milk secretion?

A

salts go in cells (not between them) and are moved into lumen –> water follows via osmotic gradient

*gradient formed primarily by lactose

74
Q

What is the paracellular pathway of milk secretion?

A

salt and water move btw cells through tight jxns

cells (primarily leukocytes) can squeeze in too

75
Q

How is lactation controlled during pregnancy?

A

PRL is inhibited by high E and P

human placental lactogen is also lactogenic

only colostrum secreted = thin, yellowish substance with a lot of IgA

76
Q

What controls lactation after birth?

A

prolactin increases

E and P decrease

suckling is most powerful physiological stimulus for PRL release (inhibits domaminergic neurons)

77
Q

How does oxytocin affect lactation?

A

enhances milk ejection by stimulating contraction of myoepithelial cells

+ feedback by suckling causes more OT to be synthesized and released

78
Q

How does lactation affect ovarian cycle?

A

increased PRL –> inhibits GNRH production –> decreased LH and FSH –> no ovarian cycle

ENRE (21 decks)

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