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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
What is the role of relaxin in childbirth?
keeps uterus in quiet states during pregnancy - ->help soften and dilate cervix - ->max concentration at 38-42 weeks
26
What is elevated relaxin at 30 weeks associated with?
premature birth
27
What secretes relaxin?
corpus luteum placenta decidua
28
What is relaxin structurally related to?
insulin
29
What does uterine stretch cause?
Ferguson reflex--> positive feedback Prostaglandin production
30
Why do twins average 19 day shorter gestation?
increased uterine stretch activates pathways faster
31
What is necessary for expulsion of the fetus?
cervical remodeling
32
Describe the initiation of labor
Placenta produces CRH - -> maternal levels rise during late preg and labor - -> promotes myometrial contractions - -> stimulates fetal ACTH secretion
33
What does fetal ACTH do during labor?
increases cortisol production to stimulate further placental CRH release increases fetoplacental estrogen to enhance myometrial contractility
34
Where does the cervix move during pregnancy?
up to just below the pelvic inlet
35
How long does it take to fully dilate the cervix and draw it up just below the pelvic inlet?
occupies most of labor time
36
How long does it take to push the fetus downward and through the pelvis?
less than 1 hour
37
What constricts uterine blood vessels as the placenta is expelling from the uterus?
oxytocin
38
What induces oxytocin release?
nipple stimulation
39
What trimester does surfactant begin to be produced?
last trimester
40
What are stimuli to start breathing at birth?
- asphyxiation during birth | - sudden drop in temp of skin
41
Why can there be delayed breathing upon birth?
- use of general anesthesia during delivery - prolonged labor - head trauma (depressed resp center)
42
Describe alveoli at birth
collapsed, filled with amniotic fluid
43
Describe the physiology of breathing at birth
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
When does breathing become normal after birth?
40 minutes - -> RR 40 - ->6-10 tidal volume
45
What do the "legs" of the umbilical arteries connect to?
IVC
46
Where does blood enter via the umbilical V?
ductus venosus
47
How does the fetus bypass the liver?
umbilical V to IVC
48
How does the fetus bypass the R ventricle?
foramen ovale (27%)
49
Blood enters IVC to the left ventricle to supply what?
carotid and brain
50
How does the fetus bypass the lungs?
ductus arteriosus -->SM dilated by prostaglandins
51
Describe closure of foramen ovale upon birth
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
Describe closure of ductus arteriosus upon birth
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
When is the ductus arteriosus closure sufficient?
1-8 days
54
When is the ductus arteriosus anatomically closed?
1-4 months
55
Describe patent foramen ovale
20% by 2 years -->increased R atrial pressure can push flap open HTN or transient increases
56
Describe patent ductus arteriosus (PDA)
heart problems soon after birth (murmur) mixing of ox and deox blood puts strain on heart--> increases pulmonary BP
57
Describe closure of ductus venosus
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
When does nephrogenesis begin?
8 weeks--> 36 weeks
59
When does urine production begin?
as early as 10 weeks-->20 weeks
60
What accounts for 70-80% of amniotic fluid?
fetal urine
61
When does renal function mature rapidly?
3rd trimester --> acid base balance, body fluid balance, electrolyte balance
62
When is functional development of the kidneys complete?
1 month
63
Due to poor fxn of liver when born, how does the infant cope?
stores fats and proteins for metabolism until it can get mother's milk
64
When are normal adult hemoglobin levels achieved?
12 weeks --> Hb A (a2b2)
65
What is the major hemoglobin in fetus?
Hb F (a2y2)
66
What are the main neonatal nutritional needs?
Ca++ and vitamin D --> via milk Iron --> enough stored for 6 months Vitamin C --> not stored in fetus, needed from milk
67
Does the fetus form its own antibodies?
NO, inherits immunity from mother | --> protects for 6 months against major diseases
68
When does infant's own immune system form?
12-20 months
69
Describe breast development from birth to puberty
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
Whatisre the fxn of alveolar epithelium in breasts?
milk synthesis and secretion
71
What is the fxn of myoepithelial cells in breasts?
b/t epithelial cells and basement membrane moves milk from alveoli into ducts on contraction
72
Describe breast formation once menstrual cycle begins
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
What are the 5 major pathways of milk secretion by alveolar cells?
1: secretory pathway 2: transcellular endocytosis and exocytosis 3: lipid pathway 4: transcellular salt and water transport 5: paracellular pathway
74
What are the 4 effects of suckling on hormone release?
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
Describe cessation of lactation
Milk accumulates when suckling stimulus discontinued - -> cell and debris phagocytosed - -> lobar acinar structures smaller - -> ductal system predominates
76
How long can full involution of breast take after lactation cessation occurs?
3 months

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