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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?

23
Q

What promotes penile enlargement?

A

Testosterone

24
Q

What hormones cause male secondary sexual characteristics?

A

Testosterone and its metabolite DHT

25
What are the androgen-dependant secondary sexual characteristics?
- 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
What initiates puberty?
Pulsitile secretion of LH
27
What stops puberty from happening in children?
Gonadotrophins are suppressed by a continous infusion of GnRH
28
What factors contribute to early onset of puberty?
- 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
What happens prior to menopause?
Peri-menopause (5 -7 years)
30
What happens to the follicle supply in menopause?
- Diminishes but does not 'run out' | - Remaining follicles not sensitive to LH and FSH
31
What happens to hormone levels in menopause?
Estrogen levels fall - Positive feedback on pituitary - Increase in FSH and LH
32
How long is a woman advised to breastfeed for for optimal benefits?
Exclusively for 6 months
33
What are the benefits of breastfeeding for the baby?
- 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
What are the benefits of breastfeeding for the mother?
- 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
When does glandular tissue develop fully?
During pregnancy
36
What do modified sebaceous glands (alveoli) empty via?
Lactiferous ducts that are dilated to form lactiferous sinuses which open on the surface of the nipple
37
What cells produce milk?
Secretory alveoli
38
What stimulates the secretory alveoli (milk producing cells)?
Prolactin
39
What are the alveoli surrounded by?
Contractile myo-epithelial cells
40
What are contractile myo-epithelial cells stimulated by?
Oxytocin
41
What hormone stimulates the ducts to proliferate and form alveoli at the ends of the ducts?
Estrogen (at puberty)
42
What do the breasts contain before puberty?
Laxctiferous ducts without alveoli (also in male breasts)
43
What happens to the breasts during pregnancy?
Under the influence of estrogen, progesterone and prolactin the glandular portion of the breast undergoes hypertrophy replacing adipose tissue
44
When does the breast tissue become fully developed?
- From week 16 fully developed but quiescent | - After parturition the breast produces colostrum before mature milk production begins
45
What are the alveoli replaced with after lactation?
Adipose tissue
46
How is prolactin initiated?
- Precipitous drop in estrogen and progesterone after delivery - Prolactin surges each time mother nurses baby due to nerve impulses from nipples to hypothalamus
47
What is produced by the hypothalamus when not nursing child?
Prolactin inhibitory hormone
48
What does lactation inhibit?
FSH and LH thus interfereing with reproductive function
49
What does the sucking stimulus inhibit and release?
- 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
What can inhibit the oxytocin let down release?
Stress - catecholamines
51
What can trigger the oxytocin let down release other than sucking?
Cry of baby
52
How is lactation inhibited during pregnancy?
- 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
What does prolactin suppress?
Hypothalamic release of GnRH and therefore pituitary FSH and LH - Prevets follicular growth, ovulation and menstrauation
54
When does LAMs effectiveness depend on?
- Must be ammenorrhoeic - Baby must be exclusively breast fed - Baby less than 6 months old

MD3002 Physiology (24 decks)

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