Menstrual and Ovarian Cycle Physiology

Question 1

What is menarche?

Answer 1

The onset of the menstrual cycle.

Question 2

What happens to the ovaries and uterus during the menstrual cycle?

Answer 2

Ovaries - produce a follicle and release it into the Fallopian tube.
Uterus - prepares the endometrium for fertilisation, if there’s none then the lining is shed.

Question 3

How long is the menstrual cycle?

Answer 3

28 days is most common.

Regular periods between 21 - 40 days is normal.

Question 4

What are the phases of the menstrual cycle?

Answer 4

Follicular phase (1st 2 weeks)
Luteal phase (last 2 weeks)

Question 5

Which hormones stimulate follicle development?

Answer 5

FSH and LH (from anterior pituitary).

Question 6

Which hormone causes endometrial thickening?

Answer 6

Oestrogen

Question 7

Which hormone causes ovulation?

Answer 7

LH - theres an LH surge during the middle of the cycle.

Question 8

What does the follicle become when it has released the oocyte?

Answer 8

The corpus luteum

Question 9

What does the corpus luteum secrete?

Answer 9

Progesterone.

Question 10

What affect does progesterone have on the endometrium?

Answer 10

It prepares the endometrium for fertilisation AFTER ovulation.

Question 11

What controls the menstrual cycle?

Answer 11

The hypothalamus - GnRH - anterior pituitary - LH, FSH

Question 12

What do LH and FSH do in the menstrual cycle?

Answer 12

FSH - stimulation of the follicle to develop

LH - causes the follicle to release the oocyte

Question 13

Where does LH bind to?

Answer 13

LH receptors on Theca cells in the ovaries.

Question 14

What does theca cells secrete?

Answer 14

Androstenedione (pro-hormone which can become progesterone or oestrogen)

Question 15

What does FSH bind to?

Answer 15

FSH receptors on granulosa cells in the ovary.

Question 16

What do granulosa cells secrete?

Answer 16

They turn the androstenedione into estradiol/progesterone

Question 17

What happens in the follicular phase (in the ovaries)?

Answer 17

FSH makes the follicles grow
FSH causes an increase in oestrogen - this is negative feedback and inhibits FSH/LH release
There is therefore only enough FSH to continue stimulating one follicle (dominant follicle)
The ovaries continue to secrete oestrogen and once it reaches a threshold it causes positive feedback - there is a surge of FSH/LH
the follicle then ruptures and releases a secondary oocyte - ovulation.

Question 18

What happens during the luteal phase (in the ovaries)?

Answer 18

The LH is still high and it turns the follicle into the corpus luteum
The follicle that ruptured becomes the corpus luteum - it secretes lots of progesterone
Progesterone has a negative feedback on the hypothalamus - this inhibits FSH/LH and oestrogen
If fertilisation happens the corpus luteum continues to secrete progesterone until the placenta forms
If fertilisation doesn’t occur the corpus luteum secretes progesterone for 10 days then stops - it becomes the corpus albicans.

Question 19

When does oestrogen behave in a positive feedback loop?

Answer 19

Only during the days of ovulation (usually days 12-14)

Question 20

What is the most common site of fertilisation?

Answer 20

Ampulla of the Fallopian tube.

Question 21

What happens during the follicular phase (to the uterus)?

Answer 21

The endometrium thickens under the influence of oestrogen to prepare for fertilisation.

Question 22

What happens during the luteal phase (to the uterus)?

Answer 22

Spiral arteries form

If theres no fertilisation - they collapse and the superficial layer of the endometrium dies and is shed.

Question 23

When does ovulation occur?

Answer 23

Usually day 14 (of a 28 day cycle)

Usually always 14 days before the first day of menstruation, regardless of the cycle length.

Question 24

When does the FSH/LH surge happen?

Answer 24

Usually 1-2 days before ovulation.

Question 25

When is fertilisation highest?

Answer 25

Day 11-15 of a 28 day cycle.

Question 26

Why do the spiral arteries collapse?

Answer 26

Because the corpus luteum becomes the corpus albicans and doesn’t secrete progesterone.
The spiral arteries collapse when progesterone is at its lowest.

Question 27

What phase can change in length?

Answer 27

The follicular phase is more likely to change

The luteal phase is almost always 14 days before menstruation

Question 28

What is another name for the follicular phase?

Answer 28

The menstrual phase

Question 29

What is another name for the luteal phase?

Answer 29

The secretory phase.

Question 30

What is the precursor for oestrogen and progesterone?

Answer 30

Cholesterol.

Question 31

What effects does oestrogen have on the body?

Answer 31

Secondary sex characteristics - growth of breasts, widening hips, fat distributed to bum and hips
Maturation of Fallopian tubes, uterus, cervix and vagina
Protects cardiovascular system
Protects bone density

Question 32

What produces oestrogen and progesterone during pregnancy?

Answer 32

The placenta

Question 33

What happens in menopause?

Answer 33

Theres no functional follicular cells left.
Theca cells and granulosa cells don’t produce oestrogen and progesterone.
The lack of oestrogen is what gives the menopausal symptoms.

Question 33

What happens in menopause?

Answer 33

Theres no functional follicular cells left.
Theca cells and granulosa cells don’t produce oestrogen and progesterone.
The lack of oestrogen is what gives the menopausal symptoms.