The Menstrual Cycle

Question 1

What is a normal cycle length?

Answer 1

24-32 days

Question 2

It is not unusual to have fluctuations in cycle length. True or false?

Answer 2

True - some months may be 27 and others 31

Still = regular cycle

Question 3

What is the mean menstrual blood loss?

Answer 3

37-43ml / cycle
40 ml = average

Occurs mostly in first 48 hours

Question 4

What percentage of women lose more than 80ml per period?

Answer 4

9-14% = 90th centile

Question 5

What percentage of those who lose more than 80ml are anaemic?

Answer 5

60-70%

Question 6

Between what age are periods most regular?

Answer 6

Between 20-40 years

Question 7

Are periods after menarche typically longer?

Answer 7

Yes

Question 8

Are pre menopause periods typically shorter or longer?

Answer 8

Shorter

Question 9

What factors affect menstrual blood loss?

Answer 9

Age - heaviness increases with age, especially fourth decade
Genetics
Parity has positive correlation ie more children likely heavier periods

Question 10

At which point in the menstrual cycle is the woman most fertile?

Answer 10

Days 9-16

From 5 days before ovulation to 1-2 days after

Question 11

Does a woman’s basal body temperature increase or decrease when a woman is about to ovulate?

Answer 11

Increase - occurs due to the LH surge

Indicates that ovulation likely to occur in next 24-48 hours

Question 12

During ovulation what happens to the cervical mucus?

Answer 12

Thins - easier passage for sperm

Question 13

Where are LH and FSH produced?

Answer 13

Anterior pituitary

Question 14

What are the functions of progesterone?

Answer 14

Involved in many different processes
Causes endometrium to become more receptive to implantation of fertilised ovum - initiates secretory phase
Inhibits LH and FSH production via negative feedback

Question 15

When does the menstrual phase occur in the cycle?

Answer 15

The very beginning
Begins with the breakdown of corpus luteum - ceases progesterone production
Loss of progesterone causes vasoconstriction of spiral arteries supplying the functional layer of the endometrium - becomes necrotic and lost through vagina, causing 3-5 days of bleeding

Question 16

When does the proliferative phase occur?

Answer 16

Immediately after the menstrual phase - days 5-14

Increased levels of oestrogen driving repair and growth of functional endometrial layer

Question 17

What are the effects of increased oestrogen in the follicular phase?

Answer 17

Thinning of cervical mucus

Thickening of endometrium

Question 18

Is the entire endometrium shed during menstruation?

Answer 18

No only the functional layer (not the basal)

Question 19

At what stage in the uterine cycle does the secretory phase occur?

Answer 19

Days 14-28

Begins after ovulation when ruptured Graafian follicle develops into corpus luteum - produced progesterone, causing endometrium to begin secreting substances that make uterus more receptive to implantation

Question 20

From the eighth week of pregnancy, what is the primary source of progesterone?

Answer 20

The placenta

The corpus luteum is primary source at the start, but then it breaks down.

Question 21

In a normal 28 day cycle when does the LH surge occur?

Answer 21

Days 11-13

Question 22

Why does the LH surge occur?

Answer 22

Oestrogen levels reach a peak, causing positive feedback - LH surge

Question 23

What does the LH surge do to the graafin follicle?

Answer 23

Causes the membrane to become thin and rupture