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Year 2 Reproduction > Puberty > Flashcards

Puberty Flashcards

1
Q

What is Puberty?

A

A stage of human development where sexual maturation and growth are completed giving an individual the ability to reproduce. This stage will involve physiological and behavioural changes.

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2
Q

When are primary sexual characteristics established?

A

Before Birth

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3
Q

When does activation of the reproductive system happen?

A

Puberty

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4
Q

Which gender tends to hit puberty first?

A

Girls

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5
Q

List 4 events of puberty

A
  • accelerated somatic growth
  • maturation of primary sexual characteristics
  • Secondary sexual characteristics appear (hair, breasts and voice changes)
  • Menstruation and spermatogenesis
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6
Q

List the environmental influences of puberty

A 
Pineal gland (tumours)
Melatonin- day length/ light levels
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7
Q

What is the most important factor in the age of onset of puberty?

A

Body weight

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8
Q

What is the critical weight for onset of menarche?

A

47kg

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9
Q

What is the average age of menarche in the UK at present and is this rising or falling?

A

13 years old

falling

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10
Q

Describe the role of leptin in triggering puberty.

A

Leptin may be involved in signalling the onset of puberty. Leptin is secreted by adipocytes, thus the higher the amount of fat the stronger the leptin signal to the CNS- this may indicate that there is enough body weight to support a pregnancy.

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11
Q

What is thelarche and when does it happen?

A

Appearance of breast buds- the first sign of female puberty

seen at age 9-13 years

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12
Q

What is adrenarche?

A

Growth spurt and menstruation onset

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13
Q

What stimulates pubic hair growth in both males and females?

A

Testosterone

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14
Q

Why do women have less circulating active testosterone?

A

Testosterone binding proteins

No testis kicking out extra testosterone

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15
Q

Which hormone closes the epiphyseal plates at the end of the growth spurt?

A

Oestrogen

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16
Q

What staging system can be used to grade puberty?

A

Tanners staging

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17
Q

When do boy genitalia start to mature?

A

10-14years

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18
Q

What is the first sign of sexual maturation in men?

A

Increase in testicular volume

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19
Q

Compare the growth spurt in men and women?

A

Men have a later onset, longer duration and faster rate of growth in their growth spurt compared to females

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20
Q

List events of male puberty

A

Increase testicular Volume
Increase in genital size
Pubic Hair
Growth spurt

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21
Q

What is accelerated somatic growth dependent on?

A

Growth hormones

Sex steroid hormones

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22
Q

What stimulates genital maturation in men?

A

Testosterone

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23
Q

Why do women stop growing earlier?

A

Oestrogen closes epiphyseal plates in both sexes- oestrogen levels higher in women so close earlier.

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24
Q

What age do boys tend to start puberty and what sign indicates its onset?

A

12.5 yrs (10-14)

Testicular volume up to 4ml (G2 Tanner)

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25
Q

How much do boys grow in a year during their accelerated growth compared to girls?

A

10.3 cm per year in boys

Girls only grow 9 cm/year

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26
Q

How long does it take to establish menarche?

A

2.4 years plus or minus 1.1 year

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27
Q

Once a boy has started puberty how long until the testis are adult size (duration of puberty in boys)?

A

3.2 years +/- 1.8 years

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28
Q

When do girls start puberty?

A

11.5 years (appearance of breast bud- B2 Tanner)

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29
Q

Which axis is switched on in puberty?

A

HPG axis

Hyothalamo-Pituatry-Gonadal Axis

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30
Q

Which hormone is released do the Hypothalamus via the hypophyseal portal system to the ant pituitary?

A

GnRH

Gonadotrophin releasing hormone

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31
Q

What is the effect of pulsatile GnRH on LH?

A

Increases frequency and amplitude of LH pulses

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32
Q

What hormone class are LH and FSH?

A

Gonadotrophins

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33
Q

What is the action of gonadotropins?

A

Gonad actions- stimulates secretion of sexual steroids

Extragonadal hormonal changes- elevation of IGF-1 and adrenal steroids

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34
Q

Deletion of which gene would result in puberty not starting?

A

GnRH-1

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35
Q

Where is the GnRH-1 gene exclusively expressed?

A

Discrete population of neutrons in the hypothalamus

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36
Q

Which hormone could you give to stimulate the onset of puberty?

A

GnRH pulsatile

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37
Q

What happens if you block GnRH?

A

No gonadotrophins secreted by the gonadotrophs of ant pituitary and lack of reproductive development

38
Q

How are the GnRH pulses regulated?

A

Biological clock which is controlled by light signals from the external environment.

39
Q

What is the action of hypothalamic releasing hormones on the specific membrane receptors of the pituitary?

A

Specific membrane receptors transduce the signal to second messengers.
This stimulates release of stored pituitary hormones, production of more hormones and the hypertrophy and hyperplasia of the pituitary cells.
Note the releasing hormones regulate their own receptors.

40
Q

How much of the anterior pituitary is made up of gonadotrophs?

A

5-10%

41
Q

Which two hormones do gonadotrophs release?

A

LH and FSH

42
Q

What two inputs are there to GnRH release?

A

Light

Leptin

43
Q

FSH acts on which cells in women?

A

Cumulus cells and Mural cells of the ovary

44
Q

Thecal cells and mural cells respond to which hormone?

A

LH

45
Q

Which hormone acts on Sertoli cells?

A

FSH

46
Q

Which cell does LH act on in the testis?

A

Leydig cells

47
Q

Which hormones negatively feedback on the hypothalamus?

A

Estradiol

Testosterone

48
Q

High levels of leptin in a child may do what?

A

Accelerate the onset of puberty

49
Q

Leptin has a pulsatile release is closely associated with surges in ….

A

LH (LH and leptin have similar patterns and thus don’t negatively feedback on one another)

50
Q

What could negatively feedback on leptin?

A

Gonadal steroid hormones

51
Q

Which hormone stimulates the rise in GH that leads to the accelerated growth hormone?

A

GHRH

52
Q

What action does GH have on the liver?

A

IGF-1 increases

53
Q

List actions of GH secretion from the pituitary.

A

Increases TSH
Increases metabolic rate (stimulating the thyroid)
Promotes gowth
Increases androgens (retains minerals for bone and muscle growth)

—– GROWTH SPURT—–

54
Q

How long is the GnRH peptide?

A

10 aminoacids

55
Q

Lh mirrrors the GnRH pulse- describe the pulse timings?

A

Every 1-3 hours

56
Q

If GnRH release is more frequent of more intense what does this say about its stimulus?

A

Strong stimulus

57
Q

Which artery connect the hypothalamus and the ant pituitary?

A

superior hypophyseal artery

58
Q

What tissue type is seen in the anterior pituitary?

A

Glandular tissue (NOT neuronal)

59
Q

Name the 6 peptides made by the anterior pituatary.

A 
Prolactin 
Growth Hormone 
TSH 
ACTH 
FSH 
LH
60
Q

What happens to LH in adolescent boys while they sleep?

A

Increases

61
Q

Whats the side effects of increased LH in adolescent boys as they sleep?

A

Nocturnal testosterone increases

62
Q

Which comes first, the nocturnal GnRH pulsatility of the phenotypic changes?

A

The nocturnal GnRH pulsatile release by years

63
Q

What rises with the onset of puberty?

A

FSH and LH

64
Q

What is precocious puberty?

A

Early puberty

65
Q

What stops the reproductive system working as if adult before puberty?

A

Low hormones from lack of GnRH

66
Q

What stimulates gonadal development? It is low levels of these that stop gonadal function as children.

A

LH and FSH

67
Q

LH and FSH increase between ….-…. age and the …. of pulses …. especially during sleep.

A

9-12
amplitude
increases

68
Q

The output of the hyothalamohypophyseal portal system controls which glands?

A

Thyroid
Adrenal Glands
Reproductive glands

69
Q

Somatic growth, lactation and water metabolism are all controlled by what?

A

Hypothalamus-pituatary unit

70
Q

What are steroid hormones derived from?

A

Cholesterol

71
Q

Name a male steroid hormone

A

Testosterone

72
Q

Do testosterone levels fluctuate after puberty?

A

Not really, they stay quite constant

73
Q

Which cells make testosterone?

A

Leydig

74
Q

What affects testosterone production?

A

Circadium rhythm

Environmental stimuli

75
Q

How many seminiferous tubules are seen in a lobule of the testis?

A

1-4

76
Q

Where does spermatogenesis happen?

A

seminiferous tubule which is 90% of the testicular volume

77
Q

What is between the seminiferous tubules?

A

Interstitial cells (leydig making testosterone) loose connective tissue and blood vessels.

78
Q

Leydig cells are needed for normal function of what?

A

Seminferous tubules

79
Q

Name the two epithelial cell types that line the seminiferous tubules.

A

Supporting/Sertoli cells

Germ cells

80
Q

What is the role of the sertoli cell?

A

Provide nutrition and hormonal support to germ cells
FSH sensitive (will increase sperm production)
Secrete inhibin that will negatively feedback on FSH production by the ant pit.

81
Q

Why do the seminiferous tubules need tight junctions?

A

Blood sperm barrier to avoid an immune response to gametes

82
Q

Which cells in the testes make testosterone?

A

Leydig

83
Q

FSH and LH act on what subtype of GPCR generally?

A

GalphaS

increases andenyl cyclase

84
Q

What are the target ovary cells for FSH and LH?

A

Granulosa cells -FSH

Theca interna-LH

85
Q

What are the effects of FSH and LH at the ovary?

A

Stimulate synthesis of sex hormones

Controls gamete production

86
Q

What releases Progesterone in females ovaries?

A

Old ruptured follicle

87
Q

High concentrations of oestrogen do what to GnRH?

A

Positive feedback and so will give an LH surge

88
Q

Oestrogen at moderate concentrations has what effect on GnRH?

A

Negative feedback

89
Q

How does progesterone (in the pill) stop ovulation at high doses?

A

Negative feedback of moderate oestrogen level is enhanced with progesterone so no GnRH pulse and thus absent LH surge

90
Q

Progesterone and oestrogen will negatively feedback on GnRH, describe there effects.

A

Oestrogen reduces GnRH release amplitude

Progesterone reduces GnRH frequency

91
Q

Where are the granulosa cells and what do they make?

A

Found in the corpus luteum

Make inhibin

92
Q

In females what is the effect of inhibin on LH

A

small inhibitory action

Year 2 Reproduction (8 decks)

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