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Endocrine > Reproductive Physiology > Flashcards

Reproductive Physiology Flashcards

1
Q

What are the key reproductive hormones?

A

GnRH, LH, FSH, oestrogen, progesterone, testosterone

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2
Q

What are the two gonadotropic hormones secreted by the pituitary gland?

A

Follicle stimulating hormone (FSH), luteinizing hormone (LH)

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3
Q

What is the function of FSH?

A 
Males = causes testes to produce sperm
Female = causes growth of ovarian follicles and causes ovary to secrete oestrogen
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4
Q

What is the role of LH?

A 
Males = causes testes to secrete testosterone
Females = causes ovulation and cause progesterone production by the corpus luteum
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5
Q

What is GnRH responsible for?

A

The release of FSH and LH from the anterior pituitary

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6
Q

What is GnRH?

A

Neuropeptide hormone synthesised and released from GnRH neurone within the hypothalamus

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7
Q

How is GnRH secreted in males?

A

Secreted in pulses at a constant rate

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8
Q

How is GnRH secrete in females?

A

Frequency of pulses varies during menstrual cycle = pulses every 1-2hrs during early follicular phase, less frequent in late follicular phase and decreases again to every 4hrs during luteal phase

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9
Q

What do high frequency GnRH pulses cause?

A

Stimulate LH pulses

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10
Q

What do low frequency GnRH pulses cause?

A

Stimulate FSH release

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11
Q

How can oestrogen affect GnRH pulsatility?

A

Oestrogen concentrations above a certain threshold will increase GnRH pulsatility driving the release of LH

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12
Q

What affect does increasing the progesterone concentration have on GnRH pulsatility?

A

Reduced the frequency of GnRH pulses

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13
Q

What is appropriate modulation of LH pulse frequency essential for?

A

Pubertal maturation and reproductive function

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14
Q

What is the onset of pubertal growth associated with?

A

Steady acceleration in GnRH pulsatility = peak at night (in boys this diurnal rhythm results in peak testosterone in the early morning causing erections)

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15
Q

What is activation of the GnRH a central mechanism of?

A

Delayed puberty = manifest in girls as no puberty by 15, manifests in boys as no sign of testicular development by age 14

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16
Q

What are some reproductive disorders associated with abnormalities of GnRH pulse frequency?

A

Hypothalamic amenorrhoea, anovulation

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17
Q

What hormones regulate GnRH pulsatility?

A

Oestrogen and progesterone

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18
Q

Which neurone regulate GnRH?

A

Kisspeptin neurons = GnRH producing Britons don’t have receptors for oestrogen and progesterone

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19
Q

What are the phases of the menstrual cycle?

A

Follicular (proliferative) phase = variable, typically 14 days +/- 7 days
Luteal (secretory) phase = more constant

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20
Q

What is the follicular phase of menstruation characterised by?

A

Follicular growth

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21
Q

What does FSH stimulate in the menstrual cycle?

A

Growth of ovarian follicles = associated with an increase in oestrogen levels

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22
Q

What does rising oestrogen levels do during the menstrual cycle?

A

Exert a negative feedback regulation (at level of hypothalamus and pituitary) to temporarily lower FSH levels

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23
Q

What happens once oestrogen reaches a certain level during the menstrual cycle?

A

Exerts a positive feedback regulation resulting in an increase in FSH levels and the LH surge

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24
Q

What does the LH surge cause in menstruation?

A

Eventually leads to ovulation and regulated the formation of the corpus luteum and progesterone production and secretion

25
Q

How does increasing progesterone levels in menstruation decrease LH secretion?

A

By influencing GnRH

26
Q

What does a follicle consist of?

A

An oocyte surrounded by follicular cells (granulosa and theca cells)

27
Q

What does follicular growth entail?

A

An increase in the number of follicular cells and accumulation of follicular fluid = causes an increase in the diameter and overall size of the follicle

28
Q

What changes occur in the endometrium during menstruation?

A

Thickens under influence from oestrogen and becomes a secretory tissue under the influence of progesterone

29
Q

What do the early stages of folliculogenesis occur independent of?

A

Gonadotrophins

30
Q

When does a follicle become gonadotrophin-dependent?

A

Once it reaches a certain size = 2-5mm diameter

31
Q

What happens if the follicle becoming gonadotrophin-dependent doesn’t coincide with rise in FSH during early follicular phase?

A

Follicle is lost

32
Q

What is the dominant follicle?

A

Follicle selected for

the ovulation

33
Q

What causes the number of follicles to continue to grow during folliculogenesis?

A

FSH = totally FSH dependent and if removed, the follicle will be lost

34
Q

What cause FSH levels to drop initially during folliculogenesis?

A

Rising oestrogen levels (associated with follicle growth) = occurs due to negative feedback at HPA axis

35
Q

What follicle is able to survive the drop on FSH levels?

A

Likely to have the most FSH receptors and the highest vascularity

36
Q

What can be used to predict the timing of ovulation within a cycle?

A

The LH surge = surge preceded ovulation by 34-36hrs

37
Q

What threshold of oestrogen is needed for the LH surge to occur?

A

200pg/ml needed to increase GnRH pulsatility and hence LH surge

38
Q

What happens to progesterone levels during the LH surge?

A

They increase

39
Q

Why is it crucial for progesterone levels to rise for ovulation?

A

Progesterone stimulates expression of enzyme that help breakdown of the follicular wall leading to the release of the oocyte

40
Q

What is the formation of the corpus luteum influenced by?

A

LH

41
Q

What do luteal cells of the corpus luteum form from?

A

Granulosa and theca cells

42
Q

Why do progesterone levels increase during the formation of the corpus luteum?

A

LH stimulates angiogenesis = ensures efficient delivery of cholesterol
LH stimulates enzymes involved in conversion of cholesterol to progesterone

43
Q

What are the functions of oestrogen?

A

Increases thickness of vaginal wall, regulates the LH surge, reduces vaginal pH through increase in lactic acid production, decreases viscosity of cervical mucus to facilitate sperm penetration

44
Q

What kind of roles does progesterone have?

A

Pro-gestation = maintains pregnancy

45
Q

What are the functions of progesterone?

A

Maintains thickness of endometrium
Responsible for infertile thick mucus = prevent sperm transport and help prevent infection
Relaxes the myometrium = functional progesterone withdraws thought to regulate birth

46
Q

What is the process of making sperm called?

A

Spermatogenesis =!occurs within testes, entire process takes 70 days

47
Q

What controls spermatogenesis?

A

Endocrine hormones = LH, FSH, testosterone

48
Q

When does spermatogenesis begin?

A

At puberty and occurs for 60 years or more

49
Q

What properties does sperm need to have?

A

Must be motile to

successfully traverse the female reproductive tract

50
Q

How are the testicles organised?

A

Extratubular compartment = interstitial and intravascular component
Intratubular compartment = Sertoli cells and germ cells (different stages of development)

51
Q

What are the endocrine and paracrine factors that influence spermatogenesis?

A 
Endocrine = LH and FSH
Paracrine = testosterone and inhibin
52
Q

How much of the testosterone from the circulation do Sertoli cells take in?

A

90% = testosterone in testes in 25-125 fold greater than in serum

53
Q

What is the role of testosterone during spermatogenesis?

A

Maintains integrity of blood-testes barrier, release of mature spermatozoa from Sertoli cells by influencing peritubular myoid cells

54
Q

What roles does dihydrotestosterone play in males?

A

Enlargement of male sex organs, secondary sexual characteristics, anabolism

55
Q

What do Sertoli cells in the seminiferous tubule secrete?

A

Androgen binding globulin (ABG) and the inhibin

56
Q

What factors stimulate spermatogenesis?

A

FSH together with testosterone

57
Q

What effect does inhibin have on FSH?

A

Decreases FSH secretion

58
Q

What stimulates testosterone secretion?

A

LH

59
Q

What does testosterone decrease the secretion of?

A

Release of GnRH and LH

Endocrine (42 decks)

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