Endocrinology of the menstrual cycle

Question 1

What is the role of the hypothalamus?

Answer 1

• Control of pituitary hormone release
• interface between outside and inside the body
• releases CRH, TRH and GnRH

Question 2

What is the role of the anterior pituitary?

Answer 2

• controls the activity of other endocrine glands

- releases LH and FSH

Question 3

What is the role of the posterior pituitary?

Answer 3

• involved in regulating water intake

- releases anti-diuretic hormone and oxytocin

Question 4

List the order of the developing follicle in the ovarian cycle

Answer 4

primordial follicle - primary follicle - secondary follicle - mature follicle (Graafian follicle) - Ovulation

Question 5

What is oogenesis?

Answer 5

the formation of gametes in the ovaries

Question 6

What phase of meiosis do the oocytes remain in until puberty?

Answer 6

Prophase I

Question 7

What happens in puberty when the hypothalamus releases GnRH?

Answer 7

• stimulates anterior pituitary to release FSH and LH

Question 8

What cells do LH and FSH act on and what happens as a result?

Answer 8

• LH acts on theca cells
• FSH acts on granulosa cells
  LH causes cholesterol to be turned into androgen which is then converted into oestrogen by FSH in the granulosa cells
  This causes the follicle to grow and develop into a primary follcile

Question 9

What happens in spermatogenesis?

Answer 9

the production of sperm cells within the seminiferous tubules of the testes
- continues throughout life after puberty

Question 10

How long does spermatogenesis take?

Answer 10

74 days

Question 11

What are the 3 stages of spermatogenesis?

Answer 11

spermatocytogenesis
spermatidogenesis
spermiogenesis

Question 12

Where does spermatogenesis take place?

Answer 12

In the sertoli cells

Question 13

Where are Leydig cells found and what role do they play?

Answer 13

found in the interstitial tissue

stimulate stem cells to differentiate into the primary spermacyte

Question 14

What role do Sertoli cells have?

Answer 14

• provide nutrients for growing sperm and help remove unwanted cytoplasm

Question 15

What is the role of the epididymus?

Answer 15

• highly convoluted tubules - allow sperm to mature and be stored until they are released

Question 16

What happens in pre-ovulation/proliferative phase?

Answer 16

secondary follicles secrete oestrogens and inhibin - this decreases production of FSH in a -ve feedback loop so the follicle stops growing
secondary follicle develops into a Graafian follicle which swells due to fluid build up in the antrum

Question 17

What happens in ovulation/secretory phase?

Answer 17

• high levels of oestrogen have a +ve feedback on anterior pituitary and hypothalamus so more GnRH and FSH and LH are released
• surge in LH results in ovulation and restarts meiosis II
• oestrogen production decreases

Question 18

What produces progetserone and what the role of progesterone in post ovulation/luteal phase?

Answer 18

• the corpus luteum secretes progesterone, oestrogen, relaxin and inhibin
• progesterone is the main hormone which inhibits FSH and LH so no more follicles develop in a -ve feedback loop
• also maintains the lining of the uterus for a fertilised egg