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ER Exam 2 > Physiology of Pregnancy > Flashcards

Physiology of Pregnancy Flashcards

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1
Q

What is the functional unit of the placenta?

A

Chorionic villi

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2
Q

What functions does the placenta provide between the mother and fetus?

A

Gut - supplies nutrients

Lung - exchanges O2 and CO2

Kidney - regulates fluid volumes and disposes of waste metabolites

Endocrine gland - synthesizes steroids and proteins that affect maternal and fetal metabolism

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3
Q

What is the purpose of pulsatile maternal blood flow into intervillous spaces?

A

Dissapates the force of the blood and reduces blood velocity so the placental tissues do not separate

Allows adequate time for exchange of nutrients

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4
Q

What is the flow of the maternal blood from the intervillous spaces back to the mom?

A

Venous orifices in basal plate => maternal placental veins => Uterine and pelvic veins

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5
Q

What acts as the functional capillary of the placenta?

A

Intervillous space

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6
Q

What is the effect of uterine contractions on maternal blood flow?

A

Attenuate arterial inflow and interrupt venous drainage

Increased volume for continual exchange

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7
Q

What umbilical vessel carries the highest O2 and nutrient content?

A

Umbilical vein

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8
Q

What umbilical vessel carries deoxygenated blood?

A

Umbilical A.

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9
Q

Partial pressure O2 is __ on maternal side vs fetal side?

A

Higher

(opposite for PCO2)

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10
Q

What causes the low PO2 of blood in intervillous space?

A

Diffusion of O2 from maternal blood into chorionic villi of fetus

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11
Q

Why does the fetus not suffer from the low PO2 of maternal blood in the intervillous space?

A

Fetal Hb has higher affinity for O2 than maternal Hb

Also: high CO in the fetus, rise in Hb concentration late in pregnancy

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12
Q

How are waste products transported across the placenta?

A

Passive movement from fetus to mother

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13
Q

How are lipid-soluble hormones transported across the placenta?

A

Simple diffusion b/w mother, placenta, and fetus

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14
Q

How is glucose transported across the placenta?

A

Facilitated diffusion from mother to fetus

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15
Q

How are AAs transported across the placenta?

A

Secondary active transport

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16
Q

How are vitamins and minerals transported across the placenta?

A

Active transport

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17
Q

How are LDLs, transferrin, hormones, and antibodies transported across the placenta?

A

Placenta takes up large molecules from the mother, increases throughout gestation until birth

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18
Q

What is the endocrine function of the placenta?

A

Maintain pregnancy

Stimulate breast development

Regulate timing and progression of parturition

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19
Q

Antibodies used to detect hCG are designed to detect what part?

A

B-subunit

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20
Q

What is the affinity of hCG for the LH receptor?

A

High

The primary action of hCG is to stimulate LH receptors on corpus luteum

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21
Q

When is hCG detectable in the maternal serum?

A

Within 24 hours of implantation (rapid accumulation in week 1)

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22
Q

Where is human placental lactogen (hPL) produced?

A

Syncytiotrophoblast

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23
Q

When can hPL be detected in maternal serum?

A

3 weeks gestation

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24
Q

What is hPL’s contribution to pregnancy?

A

Antagonistic action to insulin

Increase glucose availability by inhibiting maternal glucose uptake (diabetogenic)

Protein anabolic and lipolytic

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25
Q

What is the rate limiting step of progesterone synthesis by the placenta?

A

Conversion of cholesterol by desmolase and 3B-HSD

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26
Q

What product of DHEAs can be used to detect fetal well-being?

A

Estriol

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27
Q

What are the 3 products of DHEAs from the fetal zone?

A

Estradiol-17B

Estrone

Estriol

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28
Q

What are the functions of estrogen during pregnancy?

A

Increase uteroplacental blood flow

Enhance LDL receptor expression in syncytiotrophoblasts

Induce prostaglandin and oxytocin receptors

Increase growth and development of the mammary glands

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29
Q

What is histotrophic nutrition? How long does it occur?

A

Stimulation of uterine gland secretion by progesterone to provide nutrients to embryo

Occurs during the first trimester, replaced with hemotrophic nutrition

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30
Q

What is the “window of receptivity”? When does it occur?

A

Progesterone-induced phase of increased adhesivity of endometrial epithelium

Day 20-24

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31
Q

What happens to maternal levels of progesterone and estrogen during pregnancy?

A

Increase substantially higher than during a normal menstrual cycle

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32
Q

What is progesterone’s effect on uterine motility?

A

Inhibitory, prevents contractions

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33
Q

At what point does placenta become the main source of progesterone and estrogens?

A

8 weeks

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34
Q

What steroidogenic enzymes does the placenta lack?

A

17a-hydroxylase

17, 20 desmolase

16a-hydroxylase

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35
Q

What steroidogenic enzymes does the fetus lack?

A

3B-HSD

Sulfatase

Aromatase

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36
Q

What steroidogenic enzyme do both the fetus and placenta utilize?

A

17B HSD

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37
Q

What steroidogenic reactions are occuring in the liver of the fetus?

A

DHEA-S => 16a-OH DHEA-S via 16a hydroxylase

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38
Q

What steroidogenic reactions are occurring in the adrenal gland of the fetus?

A

LDL Cholesterol => Prenenolone sulfate

Pregnenolone sulfate => DHEA-S via 17a hydroxylase and 17,20 Desmolase

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39
Q

What is the purpose of sulfatating androgens within the fetus?

A

Reduces biological activity of steroid hormones to protect the fetus from active androgens and premature/abnormal sexual development (primarily masculinization of female fetuses)

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40
Q

What hormone mediates the increase in maternal blood volume?

A

Increased aldosterone

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41
Q

During which trimester is the increase in blood volume most significant?

A

2nd trimester

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42
Q

When does the blood volume plateau during pregnancy?

A

Last few weeks of 3rd trimester

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43
Q

By how much does the maternal blood volume increase during pregnancy?

A

40-50%

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44
Q

What is the cause of the initial fall in mean arterial pressure (MAP) during pregnancy?

A

Progesterone and estradiol act as vasodilators => Decreased peripheral resistance => Decreased MAP

45
Q

When is cardiac output the most significantly increased during pregnancy?

A

1st trimester (reflects increase in SV and HR)

46
Q

What is the effect of pregnancy on respiration?

A

Increased tidal volume => Increased alveolar ventilation

47
Q

How long does morning sickness last?

A

14-16 weeks

48
Q

What effects does pregnancy have on the GI tract?

A

GERD - prolonged gastric empty time, decreased GE tone

Constipation - decreased colonic motility and increased water absorption

Increased demand for protein, iron, and folic acid

49
Q

What hormones contribute to uterine quiescence during pregnancy?

A

Progesterone

Relaxin

50
Q

How many weeks after fertilization does parturition occur?

A

38 weeks (fetal age)

51
Q

How many weeks after the last menstrual period does parturition occur?

A

40 weeks

52
Q

What characterizes stage 0 of labor?

A

Uterine tranquility and refractoriness to contraction

53
Q

What characterizes stage 1 of labor?

A

Uterine awakening, initation of parturition, extending to complete cervical dilation

Physiological changes: increased # of gap jxns b/w myometrial cells, increased # of oxytocin receptors

54
Q

What characterizes stage 2 of labor?

A

Active labor, from complete cervical dilation to delivery of the newborn

55
Q

What characterizes stage 3 of labor?

A

Delivery of fetus to expulsion of placenta and final uterine contraction

56
Q

What is the 0 station of the fetal station?

A

When the baby’s head is even with the ischial spines (narrowest part of the pelvis)

57
Q

What happens to progesterone in the 7th month of pregnancy?

A

Plateaus and remains constant

58
Q

What stimulates the production of prostaglandins in the fetal membranes?

A

Estrogen

59
Q

What stimulates the production of prostaglandins in the uterine cells?

A

Oxytocin

60
Q

What are prostaglandins synthesized from?

A

Arachidonic acid

61
Q

What is the role of prostaglandins in parturition?

A

Initiates labor by enhancing motility/contraction of uterine smooth muscle cells

(Can induce abortion with large doses of PGF2a and PGE2)

62
Q

When are prostaglandin levels the highest? Where?

A

Just before onset of labor

Uterus, placenta, amniotic fluid, fetal membranes

63
Q

What stimulates uterine prostaglandin production?

A

Uterine stretch

64
Q

What is the Ferguson reflex?

A

Stretch of the cervix that initiates oxytocin release and causes uterine contraction

65
Q

How long does the uterus remain insensitive to oxytocin? What changes?

A

20 weeks gestation

After 20 weeks, # oxytocin receptors increases to 80x higher then 200x higher during early labor

66
Q

What is the function of oxytocin during stage 1 of labor?

A

Stimulates powerful uterine contractions that sustain labor

(Does NOT initiate labor)

Stimulates PGF2a production (synergy)

67
Q

Once stage 1 of labor is initiated, how is oxytocin released?

A

In bursts, with frequency increasing as labor progresses

68
Q

What is the function of oxytocin during the 2nd stage of labor?

A

Binds receptors on decidual cells => stimulates PGF2a production

69
Q

What is the function of oxytocin during the 3rd stage of labor?

A

Causes uterus to contract immediately after fetus is expelled to limit blood flow/loss

70
Q

Why are fetal plasma oxytocin levels higher after vaginal delivery than by cesarean section?

A

Maternal oxytocin triggered by Ferguson reflex crosses placenta into fetus

71
Q

What is the function of relaxin during parturition?

A

Softens and dilates cervix

72
Q

What is the effect of cortisol on the uterus? Where is it produced during during pregnancy?

A

Uterine stimulant

Produced in the fetal adrenal glands

73
Q

What is the mechanical reason for twins being born 19 days earlier than the average single child?

A

Increased fetal movement which elicits smooth muscle contraction

74
Q

What are Braxton Hicks contractions? When do they become labor contractions?

A

Periodic episodes of slow, rhythmic contractions

Changes when contractions start to stretch the cervix and push the baby through the birth canal

75
Q

What are the phases of delivery?

A

Dilation and effacement

Descent and Expulsion - fetus

Expulsion - placenta

76
Q

What is the effacement phase of delivery?

A

Cervical thinning in preparation for delivery

100% when cervix is paper-thin

Contractions <10 min apart

77
Q

What phase of delivery are the contractions the strongest?

A

Descent and Expulsion

78
Q

How long does the dilation and effacement phase of delivery last?

A

7-12 hours

79
Q

How long does the descent and expulsion phase of delivery last?

A

20-50 min

80
Q

How long does the expulsion of the placenta phase of delivery last?

A

15 min

81
Q

What are the two main types of prolonged labor?

A

Latent (early) phase of labor >8 hours

Active phase >12 hours

82
Q

What can cause prolonged labor?

A

Poor uterine contractions

Abnormal fetus position/size

Issues w/ birth canal

83
Q

What is labor dystocia?

A

Obstructed labor

Normal uterine contractions, but childbirth physically blocked

Can be fatal, increased risk of infection to mom

84
Q

What classifies preterm labor?

A

Labor before 37th week of pregnancy

85
Q

What classifies a ruptured uterus?

A

Failed integrity of the myometrial wall

86
Q

What is the leading sign of a ruptured uterus?

A

Deterioration of fetal heart rate

87
Q

What is the cardinal sign of a ruptured uterus?

A

Loss of fetal station on a manual vaginal exam

88
Q

What can cause ruptured uterus?

A

Uterine scar from previous C-Section (failed integrity of myometrium)

Dysfunctional/prolonged labor

Labor augmentation with exogenous oxytocin/prostaglandins

Excess manual pressure to uterine fundus

89
Q

When does preeclampsia normally present?

A

After week 20

90
Q

What is preeclampsia characterized by?

A

High blood pressure and signs of damage to another organ system (kidneys)

Abnormal placenta (poor trophoblastic invasion)

91
Q

What structure of the breast carries secretions to the outside?

A

Lactiferous duct

92
Q

What is the fundamental secretory unit of the breast?

A

The alveolus

93
Q

What do the alveoli of the breast contain?

A

Secretory alveolar cells surrounded by contractile myoepithelial cells surrounded by adipose cells

94
Q

During pregnancy, what hormones contribute to lobuloalveolar growth of the breast?

A

Prolactin

Estrogen

Growth hormone

Cortisol

95
Q

During pregnancy, what hormones contribute to ductal growth of the breasts?

A

Estrogen

Growth hormone

Cortisol

Relaxin

96
Q

What hormones are lactogenic?

A

Prolactin**

hPL**

Cortisol

Insulin

Thyroid hormones

Withdrawal of estrogen and progesterone

97
Q

What are galactokinetic hormones?

A

Promote contraction of myoepithelial cells and milk ejection

Oxytocin and vasopressin

98
Q

What are galactopoietic hormones?

A

Maintain milk production after it has been established

Prolactin

Cortisol

99
Q

What occurs during the secretory pathway of milk production?

A

Milk proteins lactalbumin and casein are sythesized into a vesicle with water

Vesical is exocytosed into the alveolar lumen

100
Q

What occurs during the transcellular pathway of milk production?

A

Maternal IgG endocytosed into alveolar lumen and secreted via exocytosis

101
Q

What occurs during the lipid pathway of milk production?

A

LCFAs from maternal diet secreted into alveolar lumen in membrane-bound sac

102
Q

What occurs during the transcellular salt and water transport route of milk production?

A

Electrolytes transported from interstitial fluid to alveolar lumen followed by water via osmotic gradient (generated by lactose)

103
Q

What occurs during the paracellular pathway of milk production?

A

Salt and water move into lumen of alveolus through tight junctions into the milk

104
Q

What is colostrum?

A

Thin, yellow milk-like substance secreted the first few days after parturition

High concentration of immunoglobulins

105
Q

What hormones inhibit prolactin during pregnancy?

A

High estrogen and progesterone

106
Q

What is the biochemical stimulus of lactation?

A

Increased levels of prolactin

Decreased estrogen and progesterone

107
Q

What is THE physiological stimulus of prolactin release?

A

Suckling

108
Q

What is the pathway of hormone release stimulated by suckling?

A
  1. Suckling stimuli activates afferent neural pathway to hypothalamus
  2. DA release inhibited => inhibit lactotrophs => release prolactin
  3. Spinal cord neurons stimulate production and release of oxytocin from posterior pituitary => stimulate myoepithelial cells to contract
  4. Spinal cord neurons inhibit hypothalamus production of GnRH => inhibits ovarian cycle

ER Exam 2 (16 decks)

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