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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
When does the source of progesterone and estrogens in pregnancy switch?
8 weeks from corpus luteum --\> placenta
26
What 3 enzymes are in the placenta and not in the fetus, and what do they do?
**sulfatase**: converts DHEA-S --\> DHEA **aromatase** and **3beta-HSD**: involved in converting DHEA --\> Estradiol
27
What 3 enzymes are in the fetus, but not in the placenta and what do they do?
17 alpha-hydroxylase/17,20 desmolase: progesterone --\> 17alpha-hydroxyprogesterone 16alpha-hydroxylase: in fetal liver; DHEA-S --\> 16alpha-OH DHEA-S
28
What does the mother do to help the placenta create hormones? How does the fetus help?
mother: supplies it with LDL = cholesterol fetus: supplies placenta w/ lacking enzymes
29
What hormone should the fetus NOT create?
estrogens - if so, fetus would be exposed to dangerous levels of E \*can't make E bc **no 3B-HSD and aromatase**
30
How does the fetus reduce the activity of steroid intermediates?
sulfates them does this to pregnenolone, DHEA, and 16A-OH-DHEA (sulfate removed in placenta)
31
What occurs to maternal blood volume during pregnancy and how?
blood volume increases - starts during 1st trimester, grows rapidly in second, evens out in 3rd mediated by increases in aldosterone
32
What occurs to mean arterial pressure of the mom during pregnancy?
increased plasma volume, but decreased peripheral vascular resistance --\> MAP usually decreases during mid-pregnancy, then rises in 3rd trimester
33
What occurs to maternal cardiac output in pregnancy?
increases a lot in 1st trimester (35-40%) --\> only slight increase during 2nd and 3rd reflects increase in stroke volume and HR
34
How does progesterone affect maternal lungs?
increase alveolar ventilation via increased tidal volume
35
What are the main maternal GI tract changes in pregnancy?
morning sickness resolved by 14-16 wks prolonged gastric empty time decreased GE sphincter toen --\> acid reflux decreased colon motility --\> constipation
36
What is the obstetric definition of labor?
series of regular, rhythmic, and forceful contractions that develops to facilitate thinning and dilation of cervix
37
What are the stages of labor?
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 f**inal contraction**
38
What physiological change occurs in the uterus during labor?
increased number of **gap jxns** btw myometrial cells increase in **oxytocin receptors**
39
What is fetal station?
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
What does estrogen do to induce labor?
increases degree of uterine contractility stimulates synthesis of oxytocin receptors
41
What do prostaglandins do to induce labor?
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
What occurs to the uterus's sensitivity to oxytocin close to labor?
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
What hormone is thought to initiate rhythmic uterine contractions?
prostaglandins | (increased oxytocin does NOT do this)
44
What does oxytocin bind to stimulate prostaglandins?
receptors on decidual cells --\> prostaglandins \*because it can stim prostaglandins, oxytocin may play role in expulsion of fetus during 2nd stage of labor
45
What 2 things stimulate oxytocin response?
estrogen --\> more oxytocin receptors cervix stretch --\> increased oxytocin release
46
What does OT do after fetus is expelled?
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
What is relaxin?
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
How do the fetal pituitary, adrenals, and placental membrane affect the uterus during labor?
pit: oxytocin adrenals: cortisol --\> may be uterine stimulant placental membranes --\> prostaglandins --\> increase intensity of contractions
49
What is significant about fetal movements and labor?
fetal movements --\> stretch uterus --\> increases its contractility twins are born on avg 19 days earlier than single child
50
What are Braxton Hicks contractions?
weak and slow rhythmic contractions that occur throughout pregnancy
51
How are labor contractions mediated?
by positive feedback: stretch --\> oxytocin and prostaglandins --\> contraction --\> stretch loop that keeps going
52
What is effacement?
cervix prepares for delivery becomes soft, short, and thinner 100% effaced = paper-thin, labor about to occur
53
Describe descent and expulsion.
cervix fully dilated: 10 cm contractions strongest at top pushing fetus down avg 20-50 min in duration
54
What is considered prolonged labor?
lasting more than 18-24 hrs 2 types: early labor \> 8hrs or active phase is \> 12 hrs
55
What is the other word for obstructed labor?
labor dystocia
56
What is considered preterm labor?
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
What are risk factors for a ruptured uterus?
uterine scar from previous C section dysfunctional/prolonged labor labor augmentation by OT or PG excessive manual pressure applied by fundus during delivery
58
What are the leading and cardinal signs of a ruptured uterus?
leading = deterioration of fetal heart rate cardinal = loss of fetal station on manual vaginal exam
59
What is preeclampsia?
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
What is a proposed cause of preeclampsia?
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
What endothelial things are thought to be changed during preeclampsia?
increased: ET-1, TBx, ANGII (due to autoAb) decreased: NO, PG2
62
What is the general organization of the breast?
alveoli --\> lobule --\> drains to ductule --\> widens into ampulla
63
What makes up a lactation alveolus?
secretory epithelial cells (alveolar cells) contractile myoepithelial cells surrounded by adipose tissue
64
What does breast development at puberty and pregnancy depend on?
puberty: estrogens and progesterone pregnancy: PRL and hPL and very high E and P --\> full development
65
What are mammogenic hormones?
promote proliferation of alveolar and duct cells Estrogen GH Cortisol Prolactin Relaxin?
66
What are lactogenic hormones?
promote initiation of milk production by alvelar cells Prolactin hCS Cortisol Insulin Thyroid Hormones withdrawal of E and P
67
What are galactokinetic hormones?
promote contraction of myoepithelial cells and thus milk ejection Oxytocin Vasopressin
68
What are galactopoietic hormones?
maintain milk production after it has been established prolactin (primary) cortisol and others
69
What are the 5 main routes of milk secretion?
1. secretory path 2. transcellular endocytosis/exocytosis 3. lipid path 4. trancellular salt and water transport 5. paracellular path
70
What is the secretory pathway of milk secretion?
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
What is the transcellular endocytosis/exocytosis path of milk secretion?
maternal immunoglobulins (IgA) taken up by endocytosis on basolateral side secreted via exocytosis --\> absorbed in baby's GI
72
What is the lipid pathway of milk secretion?
FAs form lipid droplets in alvelar cells --\> secreted in membrane-bound sacs
73
What is the transcellular salt and water path of milk secretion?
salts go in cells (not between them) and are moved into lumen --\> water follows via osmotic gradient \*gradient formed primarily by lactose
74
What is the paracellular pathway of milk secretion?
salt and water move btw cells through tight jxns cells (primarily leukocytes) can squeeze in too
75
How is lactation controlled during pregnancy?
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
What controls lactation after birth?
prolactin increases E and P decrease suckling is most powerful physiological stimulus for PRL release (inhibits domaminergic neurons)
77
How does oxytocin affect lactation?
enhances milk ejection by stimulating contraction of myoepithelial cells + feedback by suckling causes more OT to be synthesized and released
78
How does lactation affect ovarian cycle?
increased PRL --\> inhibits GNRH production --\> decreased LH and FSH --\> no ovarian cycle

ENRE (21 decks)

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