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Reproductive System > The HPG Axis, Puberty + The Menstrual Cycle > Flashcards

The HPG Axis, Puberty + The Menstrual Cycle Flashcards

1
Q

Outline the anterior pituitary gland and its hormones involve in menstruation

A
  • GnRH (every 1-3 hours) travels in hypophysis portal system + stimulates APG to secrete gonadotropin hormones:
  • follicle stimulating hormone FSH
  • luteinising hormone LH
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2
Q

Outline the HPG axis in males

A
  • FSH stimulates Sertoli cells > spermatogenesis + secretes inhibin (negative feedback on APG + FSH)
  • LH stimulates Leydig cells > testosterone released

FSH - Sertoli
LH - Leydig

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3
Q

Outline the HPG axis in females

A
  • FSH stimulates granulosa cells > follicular development
  • LH stimulates theca interna cells > release androgens (converted to oestrogen by granulosa cells)
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4
Q

Role of FSH in males

A

Stimulates Sertoli cells
- spermatogenesis
- inhibin releases > negative feedback on APG + FSH

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5
Q

Role of LH in males

A

Stimulates Leydig cells
- testosterone released

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6
Q

Role of FSH in females

A

Stimulates granulosa cells
- follicular development

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7
Q

Role of LH in females

A

Stimulates theca interna cells
- releases androgens > converted to oestrogen

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8
Q

Define gonadarche

A

Activation of the gonads

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9
Q

Define adrenarche

A

‘Awakening of adrenal glands’ > public/axillar hair + oily skin

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10
Q

Define thelarche

A

The onset of breast development occurring near the beginning of puberty in girls

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11
Q

Define menarche

A

The onset of menstruation at puberty

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12
Q

Define pubarche

A

Onset growth of pubic hair

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13
Q

What influences the timing of puberty

A
  • pineal glands
  • body weight
  • Leptin
  • environment
  • genetics
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14
Q

What is the critical weight for girls to start puberty?

A

47kg

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15
Q

Where is Leptin released from?

A

Adipose tissue

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16
Q

Outline puberty in boys

A
  • age 9-14 years
  • starts with genital development
  • pubic hair growth
  • spermatogenesis
  • growth spurt
    .
    + male secondary sexual characteristics
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17
Q

Secondary male sexual characteristics

A
  • increased + thickened hair on trunk, pubis, axillary+ face
  • increased laryngeal size (adams apple)
  • deepened voice
  • increased bone + muscle mass + strength due to testosterone
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18
Q

What scale is used to measure puberty?

A

Tanner scale

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19
Q

Outline puberty in girls

A
  • age 8-13 years
  • start with thelarche
  • adrenarche
  • growth spurt
  • menarche
    .
    + female secondary sexual characteristics
20
Q

Secondary female sexual characteristics

A
  • pubic + axillary hair
  • enlargement of labia majora + minora
  • keratinisation of vaginal mucosa
  • uterine enlargement
  • increased fat in hips/thigh
21
Q

How long is the luteal phase of the menstrual cycle?

A

Always 14 days

22
Q

What is the menstrual cycle controlled by?

A

HPG axis

23
Q

What two cycles occur in the menstrual cycle?

A

Ovarian cycle
Uterine cycle

24
Q

What are the phases of the ovarian cycle?

A

Follicular phase
Ovulation on day 14
Luteal phase

25
Q

What are the phases of the uterine cycle?

A

Menstrual phase
Proliferative phase
Secretory phase

26
Q

Outline the early follicular phase

A
  • days 0 to 5
  • no ovarian hormone production
  • granulosa cells secrete activin > ^ FSH production + FSH receptors on granulosa cells
  • FSH stimulates follicle growth, theca interna appears + increased oestrogen
  • dominant follicle granulosa cells produce inhibin instead of activin
27
Q

Outline the late follicular phase

A
  • days 5 to 14ish
  • oestrogen produced > ^ FSH receptors (initally negative feedback on HPG axis) + ^ LH receptors (prep for ovulation)
  • inhibin produced > v FSH receptors + helps LH to increase androgen production in theca cells
  • oestrogen and inhibin continue to rise
28
Q

Outline the ovulatory phase

A
  • day 14
  • LH surge > oestrogen rises + exerts positive feedback on HPG axis
  • ovulation occurs
29
Q

Outline the luteal phase

A
  • always 14 days
  • LH stimulates remaining follicle to develop into corpus luteum > secretes oestrogen +progesterone
30
Q

Outline the uterine cycle

A
  • Menstrual phase: menstrual bleeding
  • Proliferative phase: proliferation of endometrium in response to oestrogen > glands become more coiled
  • Secretory phase: glands become secretory under influence of progesterone
31
Q

What are the uterine layers?

A

Endometrium, myometrium + perimetrium

32
Q

What are the endometrial changes in the uterine cycle?

A
  • early proliferation: sparse straight glands
  • late proliferation: thicker functional layer + coiled glands
  • secretory phase: max endometrial thickness, very coiled glands + coiled arterioles
33
Q

What occurs at the end of the menstrual cycle if fertilisation doesn’t occur?

A
  • corpus luteum becomes corpus albicans
  • fall in oestrogen, progesterone + inhibin
  • menstruation
34
Q

What occurs if fertilisation is successful?

A

Syncytiotrophoblasts produce hCG
Corpus luteum lifespan extends

35
Q

Actions of oestrogen

A
  • proliferation of endometrium + myometrium
  • fallopian tube motility
  • thin, alkaline cervical mucus
36
Q

Action of progesterone

A
  • produces secretory endometrium
  • thickening + reduction of motility of myometrium
  • thick, acidic cervical mucus (prevents further entry of sperm)
  • development of breast tissue
37
Q

Normal duration of menstrual cycle

A

21 to 35 days

38
Q

What is variation in the menstrual cycle length due to?

A

Follicular phase

39
Q

What factors can disrupt the menstrual cycle

A
  • pregnancy
  • lactation
  • emotional stress
  • body weight
  • infertility
40
Q

How do the pineal glands affect the onset of puberty?

A

Children with lesion in the pineal glands undergo precocious puberty

41
Q

Why is there not a rise in FSH levels during ovulation?

A

Presence of inhibin
Causes negative feedback on APG axis

42
Q

Where is inhibin released from?

A

Sertoli cells in testicles
dominant granulosa cells in ovary

43
Q

Action of inhibin

A

Inhibits secretion of FSH from anterior pituitary gland through negative feedback

44
Q

What are the layers of the endometrium?
What are their functions?

A
  • function layer: responsive to horomones + sheds in menstruation
  • basal layer: allows regrowth at start of a new cycle
45
Q

What are the affects of low and high levels of oestrogen?

A
  • low levels: reduces amount of GnRH released > reduces FSH+LH
  • high levels: promote GnRH release > increases FSH+LH

Reproductive System (20 decks)

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