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Human Reproduction > Puberty > Flashcards

Puberty Flashcards

1
Q

What is puberty?

A

The transition phase that take a person from being a sexually immature child to a sexually mature, reproductively fertile adult

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2
Q

What is the definitive sign of puberty in females?

A

Menarche

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3
Q

What is menarche?

A

First period

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4
Q

What is the definitive sign of puberty in males?

A

First ejaculation (often nocturnal)

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5
Q

What is the main feature of the first few menstrual periods?

A

Anovulatory

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6
Q

What is the main feature of the first ejaculations?

A

Small quantities of seminal plasma

No spermatozoa

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7
Q

What causes the 10cm mean height difference between men and women?

A

Boys have their growth spurt later so are taller at point of take-off

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8
Q

Why is average strength of adult men greater?

A

Greater number of muscle cells due to androgens

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9
Q

When is the first ovulation?

A

Some months - two years after menarche

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10
Q

What causes spontaneous erections?

A

Stressful or emotionally-charged stimuli

Often not sexual matters

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11
Q

What do ovarian oestrogens cause?

A

Growth of breasts and female genitalia

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12
Q

What do ovarian and adrenal androgens do?

A

Growth of female pubic and axillary hair

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13
Q

What do testicular androgens do?

A

Development of male genitalia and body hair

Enlarging of larynx and laryngeal muscles

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14
Q

How many ovarian follicles are there in the newborn?

A

~500,000

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15
Q

How many follicles remain at puberty?

A

~83,000

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16
Q

At what stage of development do testes descend from the abdominal cavity?

A

7th or 8th month of fetal life

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17
Q

What controls descent of testes?

A

MIS and testosterone

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18
Q

What is the gubernaculum?

A

Ligament attached to testes and scrotum that pulls testes down

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19
Q

At what age does spermatogenesis begin?

A

9 years

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20
Q

At what age are mature spermatogonia produced?

A

14/15 years

21
Q

What is cryptorchidism?

A

Testes that fail to descend

3-4% fail to descend by birth

  1. 8% fail to descend by 1 year
  2. 3% fail to descend by onset of spermatogenesis
22
Q

How is cryptorchidism treated?

A
  1. Surgery

2. Treatment with gonadotrophins or GnRH to cause descent before damage is done

23
Q

How do gonadotrophin levels change in life?

A

LH and FSH pulses in first 20 weeks are the same as in adult life

Secretion then ceases and levels are low during childhood

First change is rise in FSH

Then increasingly pulsatile LH

24
Q

How do hormone levels change at menarche?

A

Sudden surge of LH and FSH sufficient for menstruation but not ovulation

25
Q

What type of hormone pulses are needed for puberty to occur?

A

LH pulses every 1 to 3 hours at relatively high amplitude

26
Q

Where is oestradiol released from?

A

Large growing follicles in ovary

27
Q

Where is oestrone released from?

A

Body fat

28
Q

What kind of androgens are released from the adrenal gland?

A

Weak androgens to maintain low circulating androgen level

Converted to testosterone at target tissues

29
Q

What is the first endocrine change in puberty?

A

Rise in DHEA

Adrenarche

30
Q

What is the source of oestrogens in males?

A

Sertoli cells

31
Q

What is gynaecomastia?

A

Slight growth of mammary glands in males

Usually goes away within two years

32
Q

What causes acne?

A

Androgens increase secretions of sebum from sebaceous glands

Glands become clogged and infected

33
Q

What are the treatments for acne?

A
  1. Antibiotics
  2. Salicylic acid
  3. Oral contraceptive
  4. Benzoyl peroxide
34
Q

What is the role of growth hormone?

A

Growth of long bones and tissues

Major effect on protein synthesis and glucose homeostasis

35
Q

What is the role of thyroid hormones?

A

Rise in metabolic rate in both sexes

Essential for body growth

36
Q

What causes childhood suppression of sexual maturation?

A

Androgens/oestrogens exert negative feedback

Hypothalamus very sensitive to steroidal inhibition during childhood

Sensitivity of hypothalamus decreases as puberty approaches

Central inhibition of GnRH pulse generator

37
Q

What does TAC3 code for?

A

Neurokinin B

38
Q

What is TACR?

A

TAC3 receptor

39
Q

What is neurokinin B

A

Member of substance B-related tachykinin family

Highly expressed in hypothalamic neurons that also express kisspeptin

40
Q

What is kisspeptin?

A

Regulator of GnRH secretion

41
Q

At what weight does puberty begin?

A

47kg in girls

55kg in boys

42
Q

How is weight sensed?

A

Leptin

Receptors in hypothalamus

43
Q

What inhibits reproductive function?

A

Melatonin

Pineal gland secretions

44
Q

What is the result of sensory deprivation on puberty?

A

Acceleration of sexual maturity

45
Q

What is the effect of excess stress and parental conflict in girls?

A

Passed through puberty more rapidly

Earlier puberty onset

46
Q

What are xeno-oestrogens?

A

Chemicals in industrial synthesis of plastics that mimic oestrogens

47
Q

What is the effect of altitude on puberty?

A

Every 100m increase in altitude delays puberty by 3 months

48
Q

What is the effect of CYP3A4 gene?

A

Produces liver enzyme that degrades testosterone, increasing oestrogen ratio

Homozygous leads to breast development before age 9.5 in 90%

Heterozygous - 56%

No copies - 40%

Human Reproduction (17 decks)

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