S4. the menstrual cycle

Question 1

average length of menstrual cycle

Answer 1

28 days
low-21
high- 35

Question 2

difference in negative vs positive feedback

Answer 2

negative feedback-high levels of output DEC input

positive feedback- output INC input

Question 3

what drugs are given in treatment of endometriosis

Answer 3

GnRH agonists/ analogues

Question 4

two phases of ovarian cycle called?

Answer 4

follicular phase
luteal phase

• preparation of the gamete for release

Question 5

describe the early follicular phase of the ovarian cycle

Answer 5

days 0-5
no ovarian hormone production
- granulosa cells secrete activin
> inc FSH production > inc FSH receptors on granulosa cells
- reduced production of androgens by theca cells> less oestrogen for now

> stimulates follicle growth
theca interna appears

• dominant follicle granulose cells switch to produce inhibin

Question 6

describe late follicular phase of ovarian cycle

Answer 6

days 5-14
dominance follicle granulose cells produce oestrogen and inhibin

Oestrogen impacts:

• inc FSH receptors on follicle
• initial negative feedback in FSH production
• inc LH receptors on granulose cells

Inhibin:

• dec FSH production
• helps to inc theca cell androgen production

Question 7

describe ovulatory phase of ovarian cycle

Answer 7

~day 14

oestrogen continues to rise independent of FSH> surge in LH production

• ovulation occurs
• granulose cells start secreting progesterone (LH action)

Question 8

describe ovulation of ovarian cycle

Answer 8

meiosis 1 complete
meiosis 2. begun but NOT complete

mature oocyte travels into Fallopian tube

Question 9

describe luteal phase of ovarian cycle

Answer 9

waiting phase

follicle is luteinised
secretes lots of oestrogen and progesterone
inhibin secreted
FSH low

Question 10

which phase of ovarian cycle is most consistent in its timing

Answer 10

luteal phase (14 days +- 2 days) 
follicular phase- more varied3 phase

Question 11

3 phases of uterine cycle?

Answer 11

menstrual
proliferative
secretory

Question 12

describe uterine layers

Answer 12

• endometrium
• myometrium
• perimetrium

Question 13

which uterine layer is shed in menstruation

Answer 13

endometrium made up of epithelium and stroma

functional layer- responsible to hormone * shed!
basal layer - develops into new functional layer

Question 14

what endometrial changes are seen in uterine cycle?

Answer 14

early proliferative- sparse glands, straight
late proliferative- thicker functional layer, glands coiled
secretory- endometrial thickens. very coiled glands. coiled arterioles.

Question 15

what changes are seen at the end of the menstrual cycle? no fertilisation

Answer 15

• corpus luteum to corpus albicans (if no fertilisation)
• dramatic fall in oestrogen, progesterone and inhibin
  > loss of negative feedback. slow rising FSH

Question 16

what is seen if fertilisation occurs

Answer 16

syncytiotrophoblast produces human chorionic gonadotrophin

extends lifespan of corpus luteum before placenta forms

Question 17

summarise oestrogen actions

Answer 17

follicular phase

• thickening of endometrium
• Fallopian tube funciton
• growth and motility of myometrium
• thin alkaline cervical mucus> ideal sperm conditions
• vaginal changes
• changes in skin, hair, metabolism

Question 18

summarise progesterone actions

Answer 18

luteal phase

• further thickening of endometrium
• thickening of myometrium and reduction of motility
• thick acidic cervical mucus > less attractive to sperm
• inc body temp
• metabolic changes
• electrolyte changes

Question 19

likely factors that disrupt length of menstrual cycle

Answer 19

• physiological e.g. pregnancy, lactation
• emotional stress
• body weight
• infertility

Question 20

HPG axis flowchart

Answer 20

(end)

androgens and oestrogen
^
gonad
^ LH and FSH
pituitary
^ GnRH
hypothalamus

(start)