Normal menstrual cycle

Question 1

What are the two phases of the endometrial cycle?

Answer 1

1) Proliferative

2) Secretory

Question 2

What happens during the proliferative phase?

Answer 2

• Occurs after menses, this is when the endometrium thickens again

Question 3

What happens during the secretory phase?

Answer 3

• Occurs after ovulation, growth of the endometrium stops and the glands become more active and full of secretions

Question 4

What are the phases of the ovarian cycle?

Answer 4

1) Follicular phase
2) Ovulation
3) Luteal (or post-ovulatory) phase

Question 5

Which part of the ovarian cycle has a constant length? Which varies?

Answer 5

• The Luteal phase is constant at 14 days

- Variation in cycle length is due to the follicular phase (longer time until ovulation)

Question 6

What is follicle stimulating hormone? Where is it produced? What signals for its production?

Answer 6

• Stimulates the growth of follicles and stimulates sex hormone secretion (predominantly estradiol)
• Produced in anterior pituitary
• Signalled by gonadatrophin releaseing hormone (GnRH)

Question 7

What is luteinizing hormone?

Answer 7

• Stimulates sex hormone production (Testosterone), which is subsequently converted to Estradiol by action of FSH
• Plays essential role in ovulation (LH surge just prior to ovulation causes rupture of mature follicle and oocyte release)

Question 8

What is a graafian follicle?

Answer 8

• A mature follicle in a mammalian ovary that contains a liquid-filled cavity and that ruptures during ovulation to release an egg

Question 9

What is ovulation?

Answer 9

• Rapid enlargement of the follicle, followed by protrusion from the surface of the ovarian cortex and rupture of the follicle with extrusion of the oocyte

Question 10

What is mittelschmerz?

Answer 10

A pain felt just prior to follicular rupture in either illiac fossa

Question 11

How is the corpus luteum formed? What does it do?

Answer 11

• The remainder of the graafian follicle, which is retained in the ovary, becomes the corpus luteum
• This structure is a major source of estrogen and progesterone secreted in the post-ovulatory phase

Question 12

When in the cycle do you test serum progesterone levels to investigate fertility? Why?

Answer 12

• Day 21: Serum progesterone secreted by the corpus luteum peaks 7 days after ovulation (day 21 in 28 day cycle)
• Therefore a day 21 level can allow you to assess if ovulation has occured

Question 13

Hormonally, what causes menses?

Answer 13

• If no conception occurs, the corpus luteum breaks down. This decreases levels of progesterone causing menses

Question 14

What hormone sustains the corpus luteum during pregnancy? How do we take advantage of this in testing?

Answer 14

• Beta human chorionic gonadotrophin (BhCG)

- Used in pregnancy tests

Question 15

What are the two layers of the endometrium? Which layer(s) are shed during menstruation?

Answer 15

1) Superficial layer - shed during menses

2) Basal layer - does not shed and is the foundation on which superficial layer rebuilds following menses

Question 16

Which hormone results in growth and proliferation of the endometrium?

Answer 16

• Estrogen
• Think unopposed estrogen therapy increases risk of endometrial Ca, as this growth goes unchecked leading to hyperplasia and then to malignancy

Question 17

Which hormone induces secretory changes in the endometrium? What purpose does this serve?

Answer 17

• Progesterone - begins to increase with secretory phase

- This prepares the endometrium for implantation of a fertilized egg

Question 18

Why does the endometrium shed (pathophysiology)?

Answer 18

• Decrease in progesterone and estrogen leads to spasmotic changes in the spiral arterioles in the superficial layer of the endometrium, causing necrosis and shedding.

Question 19

What causes uterine contractions and cramping at the time of menstrual flow?

Answer 19

• Prostaglandins

Question 20

Describe how cervical mucus changes during the menstrual cycle

Answer 20

• Early follicular phase: Cervical mucous is scant and thick, preventing entry of sperm
• Late follicular phase (just prior to ovulation): Mucous becomes watery and thin allowing for sperm to pass due to increased estrogen
• After ovulation, progesterone from the corpus luteum counteracts the estrogen and the mucous becomes thick again.

Question 21

How do progestin only contraceptives work?

Answer 21

• Using the cervical mucous, having progesterone present to counteract the thinning effect that estrogen has on the mucous results in a thick mucous which sperm cannot pass through.

Question 22

Mid-cycle penetratable cervical mucous termed “spinnbarkheit” will look like what under a microscope?

Answer 22

• Fern-like pattern (plant)

Question 23

Between ovulation and onset of menstrual bleeding there is a 0.5 C increase in body temperature in females why is this?

Answer 23

• Progesterone has a thermogenic effect at the level of the hypothalamus