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MD3002 Physiology > Puberty and lactation > Flashcards

Puberty and lactation Flashcards

1
Q

What is the first stage of puberty?

A

Adrenarche

- Increase in production of androgens by adrenal cortex

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2
Q

What is gonadarche?

A
  • Activation of the gonads by gonadotrophins
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3
Q

What are examples of gonadotrophins?

A

LH and FSH

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4
Q

What is thelarche?

A

Onset of breast development

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5
Q

What is pubarche?

A

First appearence of pubic hair

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6
Q

WHat is menarche?

A

Onset of menstruation

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7
Q

What are secondary sexual characteristics?

A
  • Developing during puberty

- Not directly required for reproduction

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8
Q

How long does puberty take?

A

4 - 5 years

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9
Q

When does adrenarche begin?

A

6 - 8 years of age

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10
Q

What is the hypothalamic-Pituitary-Adrenal axis which is involved in Adrenarche?

A
  • Hypothalamus produces CRH
  • Anterior pituitary releases ACTH
  • Adrenal gland produces adrenal androgens
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11
Q

What are increased androgen levels responsible for?

A
  • Development of pubic and axillary hair (pubarche)
  • Development of pilosebaceous unit in skin - acne
  • Increases cortical bone density
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12
Q

What is the first sign of puberty in females and when is this?

A

Breast development

- Between 8.5 - 12.5 years

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13
Q

What usually follows immediately after breast development?

A

Hair growth and rapid height spurt

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14
Q

What signals the end of growth?

A

Menarche

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15
Q

How long after the start of puberty is menarche?

A

2.5 years

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16
Q

What is the average age for menarche?

A

13

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17
Q

What is a way we are able to tell what point in puberty a girl/boy is in?

A

Tanner stages (1 - 5)

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18
Q

What is usually the first sign of puberty in men?

A

Testicular enlargement (greater than 4ml volume)

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19
Q

When is testicular enlargement in males usually?

A

10 - 15 years (mean 11)

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20
Q

How long is the interval between the onset of pubic hair and axillary and facial hair?

A

2 years

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21
Q

When is spermarche on average in men?

A

13.4

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22
Q

What promotes testicular enlargement?

A

FSH

23
Q

What promotes penile enlargement?

A

Testosterone

24
Q

What hormones cause male secondary sexual characteristics?

A

Testosterone and its metabolite DHT

25
Q

What are the androgen-dependant secondary sexual characteristics?

A
  • Facial, underarm, pubic hair
  • Deepening of voice (due to growth of larynx)
  • Thick secretion of skin oil glands (can cause acne)
  • MAsculine pattern offat distribution
  • Bone growth via growth hormone secretion (then termination via closure of epiphyseal plates)
  • Stimulation of muscle protein synthesis
  • EPO stimulation giving higher haematocrit in males
26
Q

What initiates puberty?

A

Pulsitile secretion of LH

27
Q

What stops puberty from happening in children?

A

Gonadotrophins are suppressed by a continous infusion of GnRH

28
Q

What factors contribute to early onset of puberty?

A
  • Genetics
  • Social factors
  • Obesity
  • Geographical factors (lower altitudes, urban setting, close to equator)
  • Enviromental exposures (endocrine disrupting chemicals - industry uses
  • Race - earlier in black compared to white children
  • Exact mechanism is unknown
29
Q

What happens prior to menopause?

A

Peri-menopause (5 -7 years)

30
Q

What happens to the follicle supply in menopause?

A
  • Diminishes but does not ‘run out’

- Remaining follicles not sensitive to LH and FSH

31
Q

What happens to hormone levels in menopause?

A

Estrogen levels fall

  • Positive feedback on pituitary
  • Increase in FSH and LH
32
Q

How long is a woman advised to breastfeed for for optimal benefits?

A

Exclusively for 6 months

33
Q

What are the benefits of breastfeeding for the baby?

A
  • Reduced incidence of GI, respiratory and middle ear infection
  • Decreased risk of childhood diabetes, asthma and eczema
  • Reduced risk of lactose intolerance
  • Improved intellectual and motor development
  • Decreased risk of obesity in later life
  • Possible reduced autoimmune disease
  • 27% reduced risk of sudden infant death syndrome
34
Q

What are the benefits of breastfeeding for the mother?

A
  • Promotes recovery from childbirth
  • Promotes return to ‘normal’ body weight
  • Promotes a period of infertility
  • Reduces risk of premnopausal breast cancer
  • Reduces risk of ovarian cancer
  • Possibly improves bone mineralisation
35
Q

When does glandular tissue develop fully?

A

During pregnancy

36
Q

What do modified sebaceous glands (alveoli) empty via?

A

Lactiferous ducts that are dilated to form lactiferous sinuses which open on the surface of the nipple

37
Q

What cells produce milk?

A

Secretory alveoli

38
Q

What stimulates the secretory alveoli (milk producing cells)?

A

Prolactin

39
Q

What are the alveoli surrounded by?

A

Contractile myo-epithelial cells

40
Q

What are contractile myo-epithelial cells stimulated by?

A

Oxytocin

41
Q

What hormone stimulates the ducts to proliferate and form alveoli at the ends of the ducts?

A

Estrogen (at puberty)

42
Q

What do the breasts contain before puberty?

A

Laxctiferous ducts without alveoli (also in male breasts)

43
Q

What happens to the breasts during pregnancy?

A

Under the influence of estrogen, progesterone and prolactin the glandular portion of the breast undergoes hypertrophy replacing adipose tissue

44
Q

When does the breast tissue become fully developed?

A
  • From week 16 fully developed but quiescent

- After parturition the breast produces colostrum before mature milk production begins

45
Q

What are the alveoli replaced with after lactation?

A

Adipose tissue

46
Q

How is prolactin initiated?

A
  • Precipitous drop in estrogen and progesterone after delivery
  • Prolactin surges each time mother nurses baby due to nerve impulses from nipples to hypothalamus
47
Q

What is produced by the hypothalamus when not nursing child?

A

Prolactin inhibitory hormone

48
Q

What does lactation inhibit?

A

FSH and LH thus interfereing with reproductive function

49
Q

What does the sucking stimulus inhibit and release?

A
  • Inhibits hypothalamic release of dopamine
  • Prolactin is released in proportion to the strength and duration of suckling
  • Baby essentially orders up its next meal as it suckles at its current one
  • Stimulates neurons in hypothalamus to synthesise oxytocin which is carried to pituitary
  • Oxytocin then released anf acts on myo-epithelial cells in alveoli causing ‘let down’ of milk
50
Q

What can inhibit the oxytocin let down release?

A

Stress - catecholamines

51
Q

What can trigger the oxytocin let down release other than sucking?

A

Cry of baby

52
Q

How is lactation inhibited during pregnancy?

A
  • Prolactin secreted during pregnancy but action inhibited by high levels of progesterone and estrogen and hPL (human placental lactogen)
  • Steroid levels fall after parturition and milk production begins
53
Q

What does prolactin suppress?

A

Hypothalamic release of GnRH and therefore pituitary FSH and LH
- Prevets follicular growth, ovulation and menstrauation

54
Q

When does LAMs effectiveness depend on?

A
  • Must be ammenorrhoeic
  • Baby must be exclusively breast fed
  • Baby less than 6 months old

MD3002 Physiology (24 decks)

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