Menstrual cycle

Question 1

Name the three phases of the Menstrual cycle

Answer 1

Follicular
Ovulatory
Luteal

Question 2

When in the cycle does the follicular phase start and end?

Answer 2

Day 1 of menstrual bleeding to Ovulation (mid-cycle)

Question 3

How long is the Follicular phase?

Answer 3

Typically 14 days, but it varies

Question 4

When in the cycle does the Luteal phase start?

Answer 4

After Ovulation

Question 5

How long is the Luteal phase?

Answer 5

14 days

Question 6

How long is the menstrual cycle?

Answer 6

21-35 days

variation in the follicular phase is what causes variation in the length of the whole cycle

Question 7

Briefly outline the Follicular phase of the menstrual cycle

Answer 7

Stimulation of follicle development in the ovary (FSH)
Dominant follicle is selected for ovulation
Uterus prepared for sperm transport and implantation (Oestrogen)

Question 8

Briefly outline the Ovulatory phase of the menstrual cycle

Answer 8

Meiosis I completes and Meiosis II starts

LH surge: high Oestrogen from the developing follicles enhances the sensitivity of the anterior pituitary gonadotrophs to GnRH.

Surging LH induces progesterone synthesis by Granulosa cells (FSH in the follicular phase promotes LH receptor synthesis in Granulosa cells)

Inhibin production by Granulosa cells inhibits FSH and therefore inhibits further follicle stimulation.

Question 9

Outline the effects of Oestrogen in preparing for ovulation

Answer 9

Fallopian tube: inc. motility, secretions and cilia
Myometrium: inc. growth and motility
Endometrium: inc. thickness and glandular invaginations
Cervical mucus: thinner, inc. amount and pH

Question 10

Outline the effects of Progesterone in the Luteal phase

Answer 10

Further thickening of Endometrium into secretory form
Thickening of Myometrium
Thick, acidic cervical mucus
Changes in mammary tissue
Inc. body temperature

Question 11

List some factors affecting the menstrual cycle

Answer 11

Emotional stress
Low body weight
Physiological: pregnancy, lactation

Question 12

Briefly outline the Luteal phase of the menstrual cycle

Answer 12

After ovulation, the follicle is luteinised by the action of LH and forms the Corpus Luteum
CL secretes large amounts of Oestrogen and Progesterone, with -ve feedback on LH levels
CL regresses spontaneously after 14 days, if no fertilisation

Question 13

Where is hCG produced in the embryo?

Answer 13

Syncytiotrophoblast

Placenta

Question 14

The effects of fertilisation on the Corpus Luteum…

Answer 14

The syncytiotrophoblast produces hCG which prevents the CL from regressing after LH levels diminish.
CL continues to produce Oestrogen and Progesterone which supports the early pregnancy

Question 15

What would be the effects on gonadotrophin secretion of a constant moderate dose of a
progesterone like drug?

Answer 15

Progesterone enhances negative feedback of Oestrogen
… leads to reduced LH and FSH secretion
Inhibits positive feedback of Oestrogen, so no LH surges
Ovulation is suppressed

Question 16

Bromocriptine is a dopamine mimic. As such, what is its effect on Prolactin?

Answer 16

It mimics the inhibitory effect of dopamine on lactotrophs

So Prolactin levels fall