Reproductive Physiology

Question 1

What are the key reproductive hormones?

Answer 1

GnRH, LH, FSH, oestrogen, progesterone, testosterone

Question 2

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

Answer 2

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

Question 3

What is the function of FSH?

Answer 3

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

Question 4

What is the role of LH?

Answer 4

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

Question 5

What is GnRH responsible for?

Answer 5

The release of FSH and LH from the anterior pituitary

Question 6

What is GnRH?

Answer 6

Neuropeptide hormone synthesised and released from GnRH neurone within the hypothalamus

Question 7

How is GnRH secreted in males?

Answer 7

Secreted in pulses at a constant rate

Question 8

How is GnRH secrete in females?

Answer 8

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

Question 9

What do high frequency GnRH pulses cause?

Answer 9

Stimulate LH pulses

Question 10

What do low frequency GnRH pulses cause?

Answer 10

Stimulate FSH release

Question 11

How can oestrogen affect GnRH pulsatility?

Answer 11

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

Question 12

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

Answer 12

Reduced the frequency of GnRH pulses

Question 13

What is appropriate modulation of LH pulse frequency essential for?

Answer 13

Pubertal maturation and reproductive function

Question 14

What is the onset of pubertal growth associated with?

Answer 14

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

Question 15

What is activation of the GnRH a central mechanism of?

Answer 15

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

Question 16

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

Answer 16

Hypothalamic amenorrhoea, anovulation

Question 17

What hormones regulate GnRH pulsatility?

Answer 17

Oestrogen and progesterone

Question 18

Which neurone regulate GnRH?

Answer 18

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

Question 19

What are the phases of the menstrual cycle?

Answer 19

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

Question 20

What is the follicular phase of menstruation characterised by?

Answer 20

Follicular growth

Question 21

What does FSH stimulate in the menstrual cycle?

Answer 21

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

Question 22

What does rising oestrogen levels do during the menstrual cycle?

Answer 22

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

Question 23

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

Answer 23

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

Question 24

What does the LH surge cause in menstruation?

Answer 24

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

Question 25

How does increasing progesterone levels in menstruation decrease LH secretion?

Answer 25

By influencing GnRH

Question 26

What does a follicle consist of?

Answer 26

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

Question 27

What does follicular growth entail?

Answer 27

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

Question 28

What changes occur in the endometrium during menstruation?

Answer 28

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

Question 29

What do the early stages of folliculogenesis occur independent of?

Answer 29

Gonadotrophins

Question 30

When does a follicle become gonadotrophin-dependent?

Answer 30

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

Question 31

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

Answer 31

Follicle is lost

Question 32

What is the dominant follicle?

Answer 32

Follicle selected for | the ovulation

Question 33

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

Answer 33

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

Question 34

What cause FSH levels to drop initially during folliculogenesis?

Answer 34

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

Question 35

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

Answer 35

Likely to have the most FSH receptors and the highest vascularity

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What happens to progesterone levels during the LH surge?

Answer 38

They increase

Question 39

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

Answer 39

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

Question 40

What is the formation of the corpus luteum influenced by?

Answer 40

LH

Question 41

What do luteal cells of the corpus luteum form from?

Answer 41

Granulosa and theca cells

Question 42

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

Answer 42

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

Question 43

What are the functions of oestrogen?

Answer 43

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

Question 44

What kind of roles does progesterone have?

Answer 44

Pro-gestation = maintains pregnancy

Question 45

What are the functions of progesterone?

Answer 45

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

Question 46

What is the process of making sperm called?

Answer 46

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

Question 47

What controls spermatogenesis?

Answer 47

Endocrine hormones = LH, FSH, testosterone

Question 48

When does spermatogenesis begin?

Answer 48

At puberty and occurs for 60 years or more

Question 49

What properties does sperm need to have?

Answer 49

Must be motile to | successfully traverse the female reproductive tract

Question 50

How are the testicles organised?

Answer 50

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

Question 51

What are the endocrine and paracrine factors that influence spermatogenesis?

Answer 51

``` Endocrine = LH and FSH Paracrine = testosterone and inhibin ```

Question 52

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

Answer 52

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

Question 53

What is the role of testosterone during spermatogenesis?

Answer 53

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

Question 54

What roles does dihydrotestosterone play in males?

Answer 54

Enlargement of male sex organs, secondary sexual characteristics, anabolism

Question 55

What do Sertoli cells in the seminiferous tubule secrete?

Answer 55

Androgen binding globulin (ABG) and the inhibin

Question 56

What factors stimulate spermatogenesis?

Answer 56

FSH together with testosterone

Question 57

What effect does inhibin have on FSH?

Answer 57

Decreases FSH secretion

Question 58

What stimulates testosterone secretion?

Answer 58

LH

Question 59

What does testosterone decrease the secretion of?

Answer 59

Release of GnRH and LH