4) The Menstrual Cycle

Question 1

What cycle prepares the gamete?

Answer 1

Ovarian

Question 2

What cycle prepares the endometrium?

Answer 2

Uterine

Question 3

Why is the waiting phase required?

Answer 3

Maintaining the endometrium until a signal form conceptus is received. Conceptus needs to have many cells to produce a signal (14 days)

Question 4

What is the effect of gonadotropins on the ovary?

Answer 4

Promote follicular development and cause production of ovarian hormones

Question 5

What is the effect of gonadal steroids in the menstrual cycle?

Answer 5

Affect tissues of the reproductive tract and control the cycle through positive and negative feedback

Question 6

What occurs in the early stages on the menstrual cycle?

Answer 6

LH and FSH can rise as no inhibition

Follicular development so follicle can secret oestrogen and inhibin

Question 7

What causes the LH surge?

Answer 7

Follicular oestrogen now at concentration where it can exert positive feedback causing rise in LH

Question 8

Why doesn’t FSH rise as much in the LH surge?

Answer 8

Follicular inhibin also rising

Question 9

What effect does high oestrogen have on anterior pituitary itself?

Answer 9

Enhances sensitivity of gonadotropes to GnRH so more LH release

Question 10

What promotes secretion of gonadal steroids from the corpus luteum?

Answer 10

Granulosa cells become responsive to LH

Question 11

What effect does inhibin have on the gonadal steroids?

Answer 11

Promotes production of progesterone

Question 12

Why does the corpus luteum regress and what does this lead to?

Answer 12

No further rise in LH

Oestrogen and progesterone production fall, no negative feedback and menstrual bleeding

Question 13

What prevents corpus luteum regression?

Answer 13

Synctiotrophoblast of embryo produces human chorionic gonadotropin, which exerts a luteinising effect and prevent CL regression

Question 14

What are the stages of the uterine cycle?

Answer 14

Menses, proliferative and secretory

Question 15

What are the stage of the ovarian cycle?

Answer 15

Follicular and luteal

Question 16

What happens to basal body temperature during the menstrual cycle?

Answer 16

Increases after ovulation and until menstruation

Question 17

When does the corpus luteum stop producing progesterone, if fertilisation occurs?

Answer 17

Until placenta is capable of producing sufficient quantities of progesterone

Question 18

What effect does oestrogen have on cervical mucus and why?

Answer 18

Thin, alkaline to conduct sperm

Question 19

What effect does oestrogen have on the endometrium and myometrium?

Answer 19

Thickening of endometrium

Growth and motility of myometrium

Question 20

What other effects does oestrogen have in the follicular phase?
(not on endometrium, myometrium or cervical mucus)

Answer 20

Fallopian tube function
Vaginal changes
Change in skin, hair and metabolism

Question 21

What effect does progesterone have on cervical mucus and why?

Answer 21

Thick, acidic so no sperm can get through

Question 22

What effect does progesterone have on the endometrium and myometrium?

Answer 22

Further thickening of endometrium into secretory form

Thickening of myometrium but less motility

Question 23

What other effects does progesterone have in the luteal phase?
(not on endometrium, myometrium or cervical mucus)

Answer 23

Changes in mammary tissue
Increased body temp
Metabolic and electrolyte changes

Question 24

What is the length of the menstrual cycle and what allows variation?

Answer 24

21-35 days, variable follicular phase length

Question 25

What factors can affect the menstrual cycle?

Answer 25

Pregnancy and lactation
Emotional stress
Low body weight