Parturition and Lactation Flashcards

1
Q

Parurition

A

Childbirth

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2
Q

What are the main hormones involved in maternal changes during parturition?

A
Progesterone
Estrogen
Prostaglandins
Oxytocin
Relaxin
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3
Q

Main action of Progesterone on the mother?

A

Blocks myometrial contractions and promotes its relaxation during pregnancy

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4
Q

Progesterone antagonists can induce?

A

Labor/contractions at any stage of pregnancy!

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5
Q

How do uterine cells overcome the actions of progesterone (myometrial relaxation)?

A

Desensitization of the uterine cells to progesterone

= leads to an INCREASE in estrogen receptors

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6
Q

Main action of Estrogen after uterine cell desensitization to progesterone?

A

Increases myometrial contractibility and cervical dilation

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7
Q

How does Estrogen oppose the actions of progesterone?

A

Increases uterine cell responsiveness to oxytocin and prostaglandins

  • increase oxytocin receptors on uterine cells
  • increase prostaglandin release from fetal membranes
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8
Q

Main action of Prostaglandins?

A

Stimulate strong myometrial contractions

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9
Q

Prostaglandin synthesis is stimulated by?

A

Estrogen, oxytocin and uterine stretch

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10
Q

Which prostaglandins can induce myometrial contractions at any stage of pregnancy?

A

PGF2alpha and PGE2

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11
Q

Which hormones can stimulate the formation of gap junctions?

A

Estrogen and Prostaglandins

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12
Q

Estrogen can increase what hormone receptor on uterine cells?

A

Oxytocin

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13
Q

Prostaglandin effect on the cervix?

A

Promotes effacement (thinning and softening) early in labor

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14
Q

Main function of oxytocin?

A

Stimulates uterine contractions that sustain labor

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15
Q

Describe the release frequency of oxytocin during labor

A

Released in bursts that increase in frequency as labor progresses

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16
Q

What is the primary stimulus for oxytocin release?

A

DISTENTION OF THE CERVIX

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17
Q

What is the positive feedback loop that enhances labor?

A

Ferguson reflex

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18
Q

Describe the Ferguson reflex

A
  1. Estrogen increases oxytocin receptors on uterine cells
  2. DISTENTION OF THE CERVIX
  3. Release of oxytocin
  4. Oxytocin stimulates uterine contractions and prostaglandin release from placenta
  5. Prostaglandin stimulates more uterine contractions
  6. Uterine contractions feedback to activate more oxytocin release
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19
Q

The uterus is insensitive to ____ for around 20 weeks gestation

A

Oxytocin

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20
Q

Main action of Relaxin

A

Keeps uterus quiet during pregnancy

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21
Q

Relaxin is structurally similar to?

A

Insulin

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22
Q

When are concentrations of Relaxin at their peak and what does this cause?

A

Relaxin amounts are at their peak at the END of pregnancy

- Causes cervical relaxation and dilation

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23
Q

If there are increased levels of _____ around 30 weeks, premature birth may occur

A

Relaxin

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24
Q

What are the mechanical changes of the mother during parturition?

A

Uterine size

Cervical remodeling

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25
Q

What does uterine stretch stimulate?

A

Prostaglandin production

Ferguson Reflex - causes more contractions

26
Q

Why do twins average a 19 day shorter gestation?

A

Uterus is stretched more and increasing the positive feedback loop (ferguson) earlier!

27
Q

Cervical remodeling is necessary for?

A

Expulsion of fetus

28
Q

For labor initiation, what does the placenta produce?

A

CRH - corticotrophin releasing hormone

29
Q

What 2 actions does CRH have on labor initiation?

A
  1. Promotes myometrial contractions (by increasing sensitization to prostaglandins and oxytocin)
  2. CRH accumulates in Fetal circulation
30
Q

For labor initiation, as CRH accumulates in fetal circulation, what does the fetus do?

A

Increases ACTH secretion

31
Q

For labor initiation, what does increased fetal ACTH secretion do?

A
  1. Produces fetal cortisol that increases further CRH secretion
  2. Increases fetoplacental estrogen that enhances myometrial contactions
32
Q

Most of pregnancy, the uterus undergoes periodic and weak contractions known as?

A

Braxton - Hicks

33
Q

When do Braxton-Hicks contractions become very strong?

A

During last hours of pregnancy and into active labor

34
Q

Contractions do what 3 things that occupy most of labor time?

A
  1. Stretch cervix
  2. Cervix is dilated and drawn up to pelvic inlet
  3. Retracts lower uterine segment and cervix upward
35
Q

Subsequent contractions of the uterus after the cervix is dilated and retracted up to the pelvic inlet cause what?

A

Fetus to be pushed downward

36
Q

How long does it generally take for the fetus to be pushed downward?

A

1 hour

37
Q

How is the placenta released?

A

Uterine contractions reduce area of attachment and cause separation

38
Q

____ constricts blood vessels once the placenta is released

A

Oxytocin

39
Q

____ stimulation can cause oxytocin release

A

Nipple

40
Q

Synthetic ____ can be given to aid in uterine contractions

A

Oxytocin

41
Q

Describe the organization of the mammary gland

A
  • 15-20 lobes separated by adipose and CT
  • Each lobe consists of lobules
  • In a lobule, there are alveolar cells surrounded by myoepithelial cells
  • Alevolar cells empty in lactiferous ducts
  • Lactiferous ducts for lactiferous sinus and open to nipple
42
Q

Function of the alveolar cells in the mammary gland?

A

Milk synthesis and secretion

43
Q

Function of myoepithelial cells that surround the alveolar cells in the mammary gland?

A

Contractile activity to move milk into ducts from the alveoli

44
Q

At birth, describe the mammary gland

A

ONLY lactiferous ducts are present

45
Q

At puberty, describe the mammary gland

A

Estrogen causes the lactiferous ducts to grow and branch and form alveolar cell masses

46
Q

What are the functions of estrogen and progesterone on the mammary gland?

A

Stimulate the growth and development and add adipose tissue and CT

47
Q

At pregnancy, describe the mammary gland

A

Hormones cause rapid growth and DECREASE of adipose tissue

- Alveoli become distended with early colostrum

48
Q

At lactation, what hormones are important for the mammary gland function?

A

Prolactin

Oxytocin

49
Q

Prolactin action on the mammary gland

A

Maintains milk synthesis

50
Q

Oxytocin action on the mammary gland

A

Milk ejection

51
Q

Describe the secretion frequency of prolactin during nursing

A

Intermittent

52
Q

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

A
  1. Secretory
  2. Transcellular endocytosis and exocytosis
  3. Lipid pathway
  4. Transcellular salt and water transport
  5. Paracellular path
53
Q

4 effects of the suckling stimuli?

A
  1. Activates pathway
  2. Dopamine release INHIBITED
  3. GnRH release INHIBITED
  4. Oxytocin release ACTIVATED
54
Q

What pathway is activated by suckling?

A

Breast –> Spinal cord –> Hypothalamus

55
Q

When dopamine is inhibited by the suckling stimulus, what follows?

A

Prolactin is released = milk synthesis

56
Q

When oxytocin is released from posterior pituitary by the suckling stimulus, what follows?

A

Milk ejection

57
Q

When GnRH is inhibited from being released in the hypothalamus by the suckling stimulus, what follows?

A

INHIBITION of LH and FSH release = NO OVARIAN CYCLE

58
Q

How long can mammary gland involution (shrinkage) take?

A

3 months

59
Q

When suckling stimulus stops, what occurs?

A

Milk accumulation

60
Q

Milk accumulation in the mammary gland causes?

A

Distention and rupture of alveolar walls

Compression of capillaries = alveolar hypoxia

61
Q

Once the cellular debris is phagocytized and the lobular-acinar system becomes smaller, what system of the mammary gland predominates?

A

Ductal system