The menstrual cycle

Question 1

What is the difference between male and female control of reproduction?

Answer 1

Male - continuous production

Female - Tract need to prepare for implantation, need to build in a waiting phase therefore, gamete production needs to be periodic.

Question 2

What is the difference between the feedback on HPG axis in males and females?

Answer 2

Males - always negative feedback

Females - switch between negative and positive feedback depending on where in the cycle they are.

Question 3

What two things need to be prepared?

Answer 3

Gamete (ovarian cycle)

Endometrium (uterine cycle)

Question 4

When does ovulation occur?

Answer 4

Half way through ovarian cycle. This is when the gamete is released,

Question 5

Describe the HPO axis

Answer 5

GnRH

FSH / LH

Inhibin and steroid hormones

Question 6

Why is it important that GnRH is pulsatile?

Answer 6

Needed for fertility as if GnRH receptors are exposed to continuous GnRH they become descensitised.

Question 7

What is endometriosis?

Answer 7

…

Question 8

How is endometriosis treated?

Answer 8

GnRH agonists.

Question 9

Start of menstrual cycle…

Answer 9

Start - no ovarian hormone production.

…

Question 10

What are the effects of FSH in follicular stage?

Answer 10

FSH binds to granulosa cells and causes them to multiply in a group - follicular development continues.
Theca interna appears so the follicle is now capable of oestrogen secretion.
Inhibin secretion begins.

Question 11

What happens during the mid-follicular phase?

Answer 11

Need to nominate a dominant follicle (NAME) and prevent recruitment of any further follicles.

Two things happen:

• Follicular oestrogen: Positive feedback at hypothalamus and anterior pituitary
• Gonaddotrophin lovely can rise
• Effect seen on LH only
• Follicular inhibit rising (selective inhibition on FSH production by anterior pituitary)

Question 12

What happens in preparation for ovulation?

Answer 12

Oestradiol and inhibit rise rapidly

Oestradiol production is no longer dependant on FSH

Question 13

LH surge

Answer 13

Endocrine event that promotes ovulation

Question 14

Ovulation

Answer 14

Release of oocyte form ovary

Question 15

Effects of LH surge after ovulation?

Answer 15

Secrete oestrogen and progesterone in large quantities.
Inhibit continues to be produced
…

Question 16

What happens in Luteal phase?

Answer 16

Corpus luteum produces …

Question 17

Uterine cycle…

Answer 17

….

Question 18

Layers of Uterus

Answer 18

Myometrium

Endometrium (epithelial lining) - made from functional layer and basal layer

Question 19

Difference between two layers of endometrium?

Answer 19

…

Question 20

How does Uterus change over the menstrual cycle?

Answer 20

Early
Late
Early
Late

Question 21

How do you get to end of cycle?

Answer 21

No more LH - corpus lute regresses
Dramatic fall in gonadal hormones (Oestrogen and Progesterone).
Relieving negative feedback and resets to start again.

Question 22

How does end of cycle change if fertilisation occurs?

Answer 22

Syncitiotrophoblast

Question 23

Pregnancy hormones?

Answer 23

Corpus Leteum, supported by placental hCG. produced steroid hormones to support the pregnancy.

Question 24

What different phases are there in ovarian and Uterine cycle>

Answer 24

…

Question 25

What does oestrogen do during the follicular phase?

Answer 25

Fallopian tube function
Thickening of endometrium
Growth and motility of myometrium

Question 26

What does progesterone do during the Luteal phase?

Answer 26

Further thickening of endometrium into secretory form.

Question 27

What is a ‘normal’ cycle duration?

Answer 27

Normally 21-35 days
Variation in cycle duration due to variation in the length of the follicular phase. as Luteal phase its strictly 14+- 2 days

Question 28

What factors affect the menstrual cycle?

Answer 28

Pregnancy
Lactation
Emotional stress
Low body weight