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Mammalian Reproduction > Parturition & Lactation > Flashcards

Parturition & Lactation Flashcards

1
Q

What are 4 roles of progesterone during pregnancy?

A
  • Thickens endometrium throughout pregnancy
  • Prevents ovulation
  • Stimulates growth of maternal breast tissue, preventing lactation
  • Strengthens pelvic wall muscles in preparation for labour
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2
Q

In assisted reproduction, what is the role of progesterone?

A
  • 1st trimester progesterone supplementation support early pregnancy by reducing miscarriage
  • Reduces risk of pre-term delivery
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3
Q

What hormones are prominent in the third trimester?

A
  • Oestrogen, which results in an increase in prostaglandins that affect uterine contractility + cervical ripening
  • Progesterone levels decrease
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4
Q

What is oestriol?

A

A weak oestrogen that promotes uterine growth + prepares body for giving birth

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5
Q

What is Braxton-Hicks contractions?

A
  • Sporadic uterine contractions (false labour)
  • Increase in oxytocin
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6
Q

What 3 stages can parturition be divided into?

A

1 - Onset of contraction, dilation + shortening of cervix
2 - full dilation of cervix to delivery of baby
3 - delivery of placenta

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7
Q

Describe the first stage of parturition.

A
  • Cervical effacement (ripening of cervix)
  • Contractions retract the cervix + lower part of uterus to form a continuous birth canal with the vagina
  • Cervix needs to undergo changes to make it softer + more flexible (cervical remodelling)
  • Needed for dilation + expulsion of foetus
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8
Q

What does cervical remodelling involve?

A
  • Softening
  • Ripening
  • Dilation & labour
  • Post partum repair
  • Prostaglandins + relaxin
  • Possibly Nitric Oxide (NO)
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9
Q

When does stage 1 of parturition end?

A

When cervix is fully dilated

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10
Q

Describe the second stage of parturition.

A
  • Parturition
  • Period from full dilation of cervix to expulsion of neonate (baby)
  • A few days prior to parturition, stomach ‘sinks’ as pelvic ligaments relax + baby settles lower in uterus
  • Mammary glands enlarge as colostrum is produced
  • Requires contractions of uterine myometrium that are sufficiently strong to expel foetus
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11
Q

What hormone is produced to prepare a woman for birth?

A

Ovary + placenta produce relaxin

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12
Q

What does relaxin do?

A

Relaxes ligaments in pelvis + softens and widens cervix to allow passage of foetus

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13
Q

What other hormones increase to promote labour?

A

Oestradiol
Prostaglandins
Prolactin

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14
Q

What does a breech birth refer to?

A

Any other part of the body, other than the head, approaches cervix first

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15
Q

What are 2 triggers for parturition?

A

1- High oestrogen (oestadiol)
- Stimulates expression of oxytocin receptors in myometrium
- Increase in receptors makes myometrium more responsive to oxytocin
- Oxytocin stimulates synthesis of placental prostaglandins

2 - Oxytocin + prostaglandin stimulate smooth muscle contraction
- Pressure of head in contact with cervix triggers release of oxytocin from pituitary gland
- Oxytocin stimulates uterine contractions (labour)
- When contractions start, head of foetus is pushed against cervix, stimulating more contractions + more oxytocin to be released (+ feedback)
- Contractions consequently increase in intensity + frequency
- As foetus moves through cervix, stretch receptors in vagina activate neural reflexes that trigger abdominal wall contractions

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16
Q

Describe the third stage of parturition.

A
  • Exoulsion of the placenta
  • Oxytocin falls after birth
  • Secondary surge triggers series of uterine contractions that separates placenta from myometrium
  • Myometrium continues to contract to constrict uterine blood vessels supplying placental attachment site
  • Prolactin stimulates milk synthesis + secretion
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17
Q

What is thought to be the role of Corticotropin Releasing Hormone?

A
  • Establish positive-feedback loops that initiate parturition + labour
  • Interacting with oestrogen, adrenal steroids, prostaglandins + oxytocin
  • Timing of birth by regulating control of contractile properties of myometrium
  • May contribute to initiation of labour by acting indirectly to enhance foetal ACTH (adrenocorticotropic hormone) and adrenal cortisol production
  • Stimulates production of foetal adrenal DHEA-S
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18
Q

What is CRH secreted by?

A

Foetal portion of placenta

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19
Q

What is the role of cortisol in parturition?

A

Prepares foetal lung for extra-uterine life

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20
Q

What is the role of DHEA-S?

A
  • Induces myometrial oxytocin receptors, thereby preparing the uterus for parturition, in late gestation
  • Used by placenta to produce oestrogen
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21
Q

How is the delivery date more accurately predicted currently?

A

Based on maternal CRH levels as early as the end of 1st trimester

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22
Q

How is labour induced?

A
  • Vaginal infusions of prostaglandins
  • Oxytocin then used to rigger myometrial contractions to induce parturition
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23
Q

Are oxytocin levels during c-sections higher or lower?

A

Lower due to the lack of cervical + myometrial contractions

24
Q

What is the issue with reducing less oxytocin during c-sections?

A

Oxytocin involved in mother offspring bonding + preparation for lactation - lead to maternal problems

25
Q

What are some foetal changes at parturition?

A
  • Foetal circulation doesn’t involve lung because O2 is provided through placenta
  • 2 ventricles pump in parallel + shunts divert most circulation away from developing lungs to placenta
  • 3 shunts bypass lungs, divert blood from left to right side of heart + bypass most of hepatic system
26
Q

Describe foetal circulation

A
  • Blood oxygenated in placenta
  • Oxygenated + nutrient-enriched blood from placenta returns to foetus through left umbilical vein
  • A little blood enters liver but most bypasses hepatic system through ductus venosus + enters inferior vena cava
  • From vena cava, blood enters right atrium.
  • Most is shunted directly to left atrium through foramen ovale, bypassing right ventricle
  • From left atrium, blood enters left ventricle + is delivered to foetal tissues via aorta
  • Oxygenated depleted + nutrient-poo foetal blood is returned to placenta via right + left umbilical arteries
  • A small amount of blood in right atrium enters right ventricle + goes to lungs but most of blood bypasses lungs through ductus arteriosus
27
Q

How and why do the shunts close at birth?

A
  • Placental blood flow ceases + lung respiration begins in neonate
  • Decreases in prostaglandins + changes in blood pressure forces septa against shunts, closing them off
  • Shunts must close at birth to establish normal adult circulation
28
Q

What is it called if the foramen ovale fails to close?

A

Patent foramen ovale

29
Q

What happens if the ductus arteriosus closes prematurely?

A
  • Increased pressure on right ventricle = pulmonary hypertension
  • If left untreated = foetal death
30
Q

What happens if the ductus venous fails to close?

A

Hepatic dysfunction

31
Q

Describe foetal respiration

A
  • Ahead of parturition, foetus makes resp movements that move amniotic fluid into + out of lungs
  • Foetal corticosteroids stimulate the production of pulmonary surfactant (a phospholipid attached to a protein) that reduces surface tension of pulmonary fluid in lungs
32
Q

What happens if insufficient surfactant is produced?

A
  • Result in problems with lung expansion at birth (idiopathic respiratory distress syndrome
  • In premature infants, lung maturation can be improved by injections of corticosteroids in mother
33
Q

What is tachypnea?

A

Abnormally rapid breathing

34
Q

What occurs is normal removal of fluid does not take place?

A
  • Happens in c-sections
  • Baby’s lungs may not develop properly
  • Transient Tachypnea of newborn (TTN)
35
Q

What does puerperium mean?

A

Post partum

36
Q

What is uterine involution?

A

When the uterus shrinks to normal size after parturition

37
Q

How long does it take for hormone levels to return to normal after parturition?

A

4-6 weeks

38
Q

What is lochia?

A

Vaginal discharge containing blood, mucus + uterine tissue

39
Q

What do marsupials have instead of a placenta?

A

Enlarged yolk sac

40
Q

What is a kangaroos gestation period?

A

31-36 days
Give birth to embryonic, immature young that climb to a nipple in pouch + attach to it

41
Q

What is diapause?

A
  • E.g. a doe, usually have 3 offspring at the same time
  • Delaying development of fertilised egg if environmental conditions are unfavourable or until older joey vacates pouch
42
Q

Describe the anatomy of the breast

A
  • Made up of fat + breast tissue
  • Nerves, blood vessels + connective tissue
  • Has a number of lobules that branch out from nipple
  • Each lobule holds tiny, hollow sacs (alveoli) where milk is secreted + stored
43
Q

Describe lactation during gestation

A
  • Elevated placental oestrogen stimulates milk duct development
  • Elevated placental progesterone stimulates alveoli formation
44
Q

What hormones stimulate + synthesise enzymes essential for milk production by alveolar epithelial cells?

A

Prolactin + Human Placental Lactogen (hPL)

45
Q

What is the role of prolactin and hPL?

A
  • Stimulate + synthesis enzymes essential for milk production by alveolar epithelial cells
  • Promote foetal groeth by stimulating secretion of insulin-like growth factors (IGF-1 and 1GF-2)
46
Q

Where is milk synthesised in breasts?

A

Epithelial cells

47
Q

What 2 hormones are essential for maintaining lactation?

A

Prolactin + oxytocin

48
Q

What hormones are released through suckling?

A

Oxytocin + prolactin

49
Q

What does oxytocin and prolactin do when young is suckling?

A
  • Causes smooth muscle contraction that ejects milk
  • Prolactin stimulates synthesis of more milk to replace milk ejected
50
Q

What does the breast produce prior to milk production?

A

Colostrum
A thick, yellowish fluid + is only produced for a few days
Gradually replaced by milk

51
Q

What does colestrum contain?

A
  • Protein
  • Fats
  • Vit A
  • Immune cells (lymphocytes)
  • Antibodies such as IgA, IgG and IgM
  • Growth factors, such as insulin-like growth factors (IGF-1 and IGF-2)
52
Q

What is meconium?

A

New-borne first stools
Contains excess bile + waste products from when still in uterus
Colostrum has a laxative effect to help expel this

53
Q

What are the advantages of breast feeding?

A

Reduced risk of:
- Asthma
- Autoimmune diseases
- Type 1 diabetes
- Some cancers, e.g. Lymphoma

54
Q

What are the disadvantages of bottle feeding?

A
  • Digestive tract infections
  • Respiratory tract infections
55
Q

What are the advantages of breast-feeding for the mother?

A
  • Oxytocin hastens involution (shrinking of uterus)
  • Prolactin inhibits GnRH
  • Helps lose weight

Mammalian Reproduction (16 decks)

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