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GIGU > Parturition, Lactation and Neonatal Physiology > Flashcards

Parturition, Lactation and Neonatal Physiology Flashcards

1
Q

What does parturition involve?

A
  • myometrium becomes highly contractile
  • remodeling of cervix–> softens and dilates
  • rupture of fetal membranes
  • expulsion of urterine contents
  • return of uterus to prepregnant state
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2
Q

What categories of effects lead up to intense contractions during childbirth?

A
  • progressive hormonal changes
    *relaxin, oxytocin,
    prostaglandins,
    progesterone,
    estrogens
  • progressive mechanical changes
    *cervical remodeling,
    uterine size
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3
Q

Describe Braxton Hicks contractions

A

toward end of pregnancy

not powerful enough to induce labor
–>thought to prepare uterus for childbirth

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4
Q

Describe uterus during most of pregnancy

A

Relaxed, quiescent, insensitive to contraction hormones (prostaglandins, oxytocin)

Hypertrophy of myometrial cells as uterus expands to fit fetus

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5
Q

What is necessary for onset of labor?

A

Reciprocal changes in uterine progesterone and estrogen receptors

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6
Q

What hormone blocks contractions of labor and promotes myometrial relaxation during pregnancy?

A

progesterone

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7
Q

Injection of what antagonist can induce labor at any stage of pregnancy?

A

nuclear progesterone antagonist

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8
Q

What hormone increases myometrial contractility and cervical dilation?

A

estrogen

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9
Q

What happens to uterine cells in terms of progesterone and induction of childbirth?

A

desensitization of cells to progesterone allows increase in estrogen receptor expression–> childbirth

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10
Q

What hormone is necessary to increase responsiveness to progstaglandins and oxytocin to kickstart childbirth?

A

estrogen

–> stimulate gap jxn formation

–>increase # oxytocin receptors in myometrium and decidual tissue

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11
Q

What stimulates expression of proteolytic enzymes in the cervix?

A

estrogen

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12
Q

What hormone increases production of prostaglandins in the fetal membrane?

A

estrogen

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13
Q

What initiates labor via stimulation of strong myometrial contractions?

A

prostaglandins

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14
Q

Large doses of what during pregnancy can induce labor at any gestation?

A

prostaglandins

PGF2a and PGE2

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15
Q

What potentiates oxytocin induced contractions by promoting formation of gap jxns?

A

PGF2a

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16
Q

What stimulates synthesis of prostaglandins?

A
  • estrogen in fetal membranes
  • oxytocin in uterine cells
  • uterine stretch
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17
Q

What stimulates effacement of cervix early in labor?

A

prostaglandins

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18
Q

Uterus is insensitive to what until 20 weeks?

A

oxytocin

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19
Q

What increases the number of oxytocin receptors in myometrium and decidual tissue?

A

estrogen

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20
Q

What does oxytocin do in uterine myometrium?

A

smooth muscle contraction to sustain labor

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21
Q

What does oxytocin do to decidual tissue?

A

stimulates prostaglandin (PGF2a) production

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22
Q

Describe the frequency of oxytocin release during labor

A

Released in bursts that increase in frequency as labor progresses

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23
Q

What is the primary release for oxytocin?

A

distention of cervix

Ferguson reflex, + feedback

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24
Q

What is the Ferguson reflex?

A

oxytocin is released as the cervix is distended

–>positive feedback loop to enhance labor

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25
Q

What is the role of relaxin in childbirth?

A

keeps uterus in quiet states during pregnancy

  • ->help soften and dilate cervix
  • ->max concentration at 38-42 weeks
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26
Q

What is elevated relaxin at 30 weeks associated with?

A

premature birth

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27
Q

What secretes relaxin?

A

corpus luteum
placenta
decidua

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28
Q

What is relaxin structurally related to?

A

insulin

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29
Q

What does uterine stretch cause?

A

Ferguson reflex–> positive feedback

Prostaglandin production

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30
Q

Why do twins average 19 day shorter gestation?

A

increased uterine stretch activates pathways faster

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31
Q

What is necessary for expulsion of the fetus?

A

cervical remodeling

32
Q

Describe the initiation of labor

A

Placenta produces CRH

  • -> maternal levels rise during late preg and labor
  • -> promotes myometrial contractions
  • -> stimulates fetal ACTH secretion
33
Q

What does fetal ACTH do during labor?

A

increases cortisol production to stimulate further placental CRH release

increases fetoplacental estrogen to enhance myometrial contractility

34
Q

Where does the cervix move during pregnancy?

A

up to just below the pelvic inlet

35
Q

How long does it take to fully dilate the cervix and draw it up just below the pelvic inlet?

A

occupies most of labor time

36
Q

How long does it take to push the fetus downward and through the pelvis?

A

less than 1 hour

37
Q

What constricts uterine blood vessels as the placenta is expelling from the uterus?

A

oxytocin

38
Q

What induces oxytocin release?

A

nipple stimulation

39
Q

What trimester does surfactant begin to be produced?

A

last trimester

40
Q

What are stimuli to start breathing at birth?

A
  • asphyxiation during birth

- sudden drop in temp of skin

41
Q

Why can there be delayed breathing upon birth?

A
  • use of general anesthesia during delivery
  • prolonged labor
  • head trauma (depressed resp center)
42
Q

Describe alveoli at birth

A

collapsed, filled with amniotic fluid

43
Q

Describe the physiology of breathing at birth

A

need 25mmHg negative inspiratory pressure to overcome surface tension and open alveoli

  • ->1st inspiration (-60(
  • ->1st insp movements (40mL air)

Deflation requires strong positive pressure to overcome viscous resistance of fluid in broncioles

44
Q

When does breathing become normal after birth?

A

40 minutes

  • -> RR 40
  • ->6-10 tidal volume
45
Q

What do the “legs” of the umbilical arteries connect to?

A

IVC

46
Q

Where does blood enter via the umbilical V?

A

ductus venosus

47
Q

How does the fetus bypass the liver?

A

umbilical V to IVC

48
Q

How does the fetus bypass the R ventricle?

A

foramen ovale (27%)

49
Q

Blood enters IVC to the left ventricle to supply what?

A

carotid and brain

50
Q

How does the fetus bypass the lungs?

A

ductus arteriosus

–>SM dilated by prostaglandins

51
Q

Describe closure of foramen ovale upon birth

A

reversal of pressure gradient across atria pushes it shut
–>eventually seals

**increased venous return to L atrium and elevated L atrial pressure

***Decreased right atrial pressure

52
Q

Describe closure of ductus arteriosus upon birth

A

Aortic pressure rises above pulmonary

  • -> blood flows wrong way, oxygenated aortic blood flows through ductus
  • –>causes vasoconstriction (PCO2) along with falling progesterone levels that eventually close ductus
53
Q

When is the ductus arteriosus closure sufficient?

A

1-8 days

54
Q

When is the ductus arteriosus anatomically closed?

A

1-4 months

55
Q

Describe patent foramen ovale

A

20% by 2 years
–>increased R atrial pressure can push flap open

HTN or transient increases

56
Q

Describe patent ductus arteriosus (PDA)

A

heart problems soon after birth (murmur)

mixing of ox and deox blood puts strain on heart–> increases pulmonary BP

57
Q

Describe closure of ductus venosus

A

Immediately after birth, portal blood flows through ductus venosus

–>1-3 hours, muscle wall contracts and closes

–> portal venous pressure rises, forcing through liver sinusoids

**rarely fails to close

58
Q

When does nephrogenesis begin?

A

8 weeks–> 36 weeks

59
Q

When does urine production begin?

A

as early as 10 weeks–>20 weeks

60
Q

What accounts for 70-80% of amniotic fluid?

A

fetal urine

61
Q

When does renal function mature rapidly?

A

3rd trimester

–> acid base balance, body fluid balance, electrolyte balance

62
Q

When is functional development of the kidneys complete?

A

1 month

63
Q

Due to poor fxn of liver when born, how does the infant cope?

A

stores fats and proteins for metabolism until it can get mother’s milk

64
Q

When are normal adult hemoglobin levels achieved?

A

12 weeks

–> Hb A (a2b2)

65
Q

What is the major hemoglobin in fetus?

A

Hb F (a2y2)

66
Q

What are the main neonatal nutritional needs?

A

Ca++ and vitamin D
–> via milk

Iron
–> enough stored for 6 months

Vitamin C
–> not stored in fetus, needed from milk

67
Q

Does the fetus form its own antibodies?

A

NO, inherits immunity from mother

–> protects for 6 months against major diseases

68
Q

When does infant’s own immune system form?

A

12-20 months

69
Q

Describe breast development from birth to puberty

A

Mammary gland entirely lactiferous ducts with few alveoli at birth
–> remains until puberty

Estrogens–> lactiferous ducts to sprout and branch, ends develop into alveoli

70
Q

Whatisre the fxn of alveolar epithelium in breasts?

A

milk synthesis and secretion

71
Q

What is the fxn of myoepithelial cells in breasts?

A

b/t epithelial cells and basement membrane

moves milk from alveoli into ducts on contraction

72
Q

Describe breast formation once menstrual cycle begins

A

exposed to estrogen and progesterone
–> induces additional alveolar growth

breast tissue increases
–>CT and adipose

cyclical changes

  • -> increase in volume
  • -> breast tenderness
  • -> may have some secretory activity
  • -> involution
73
Q

What are the 5 major pathways of milk secretion by alveolar cells?

A

1: secretory pathway
2: transcellular endocytosis and exocytosis
3: lipid pathway
4: transcellular salt and water transport
5: paracellular pathway

74
Q

What are the 4 effects of suckling on hormone release?

A

1: suckling stimuli or sight of child
- –> afferent neural pathway from breast to spinal cord and hypothalamus

2: Dopamine release inhibited, prolactin released to stimulate milk production

3: Stimulation of production of oxytocin from posterior pituitary
- -> activates myoepithelial cells (let down)

4: Inhibition of GnRH production
- -> inhibits ovarian cycle via decrease in LH and FSH

75
Q

Describe cessation of lactation

A

Milk accumulates when suckling stimulus discontinued

  • -> cell and debris phagocytosed
  • -> lobar acinar structures smaller
  • -> ductal system predominates
76
Q

How long can full involution of breast take after lactation cessation occurs?

A

3 months

GIGU (37 decks)

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