The Menstrual Cycle

Question 1

What are the aims of the menstrual cycle?

Answer 1

Select a single oocyte

Regulate spontaneous ovulation

Correct number of chromosome in egg

Cyclic changes in the cervix and fallopian tube, so it permits the transport and implantation of the egg.

Preparation of the uterus

Support of the fertilised dividing egg.

Question 2

What are the two phases of the menstrual cycle?

And how long does the menstrual cycle last?

Answer 2

The menstrual cycle is divided into two phases; follicular phase and the luteal phase.

A typical menstrual cycle is 28 days.

Question 3

When does the menstrual cycle start?

Answer 3

the first day of menses.

Question 4

What happens during the follicular phase?

Answer 4

A cohort of prenatal follicle develops up to the point one of them ovulate.

Question 5

which hormone is produced by the dominant follicle.

Answer 5

oestradiol

Question 6

what is the luteal phase named after?

Answer 6

the corpus luteum.

Question 7

what happens after ovulation?

Answer 7

the luteal phase start, the corpus luteum is formed from the remainder of the follicle.

Question 8

how is the corpus luteum formed?

Answer 8

the follicle open, cumulus-oocyte complex is released and picked up by the tube. the remainder is the CL.

Question 9

which hormone is produced and dominates the luteal phase?

Answer 9

Progesterone.

Question 10

What happens at the end of the luteal phase?

Answer 10

the corpus luteum dies.

Question 11

which stage of the cycle varies in days?

Answer 11

the luteal phase is fixed, follicular phase is variable. this is due to the corpus luteum have a fixed lifespan.

Question 12

What inhibits the hypothalamic/pituitary/ovarian axis?

Answer 12

The antral follicle’s estradiol inhibits. After the ovulation progesterone from the corpus luteum inhibits the axis again, until it dies.

Question 13

Describe what happens from the end of luteal phase to the start of luteal phase?

Answer 13

At the end of the cycle, No CL means no progesterone induced negative feedback. FSH level increase which stimulates the growth of follicles.

Overtime as it grows oestradiol is produced, this inhibits FSH release via feedback to the HP axis. So its level falls again.

While this is happening one follicle has grown enough to develop LH follicle. With a small rise in LH, that particular follicle can keep growing, into the dominant follicle.

The dominant follicle makes a large amount of E2, and after 2 days of this the conc level reaches 300pmol, this transforms the axis into a positive feedback with the E2. This produces a large LH surge which causes the egg to be released. The remaining follicle becomes the corpus luteum and the luteal phase begin.

Question 14

when does the final maturation occur?

Answer 14

the end of meiosis I occur at ovulation caused by the LH surge.

Question 15

what receptor does theca have and which hormone does it release?

Answer 15

Theca cells have LH receptors, so LH drives androgen and progesterone production.

Question 16

Once the dominant follicle is selected why does it need neoangiogenesis?

Answer 16

Is needs it to sustain its nutritional needs from growing so rapidly. It doubles in diameter in 7 days, from 7mm to 14mm. It needs a lot of growth factors, nutrients, and steroids. At the same time, oestrogen produced can enter the circulation.

Question 17

What is the cascade of events for ovulation?

Answer 17

Blood flow to the follicle increases dramatically, increase in vascular permeability increase intrafollicular pressure.

The appearance of an apex/sigma on the ovarian wall.

Local release of protease.

Enzyme breakdown of proteins on the ovary wall.

18 hours after peak LH, a hole appear in the follicle wall and the ovulation occurs.

Question 18

how does the follicle move as it grows?

Answer 18

As follicle grow it moves into the medulla of the ovary as it is richer with blood vessels. Eventually, the dominant follicle moves back out so it can release the oocyte from the cortical wall.

Question 19

What happens to the egg after it leaves the follicle?

Answer 19

The egg gets collected by the fimbria of the fallopian tube. The egg progresses down the tube by peristalsis and action of cilia.

Question 20

How does a patient work out when they are going to ovulate.

Answer 20

this is normally done if the cycle is regular, 2 weeks from the first day of menses. if not regular ultrasound scan can help monitor the induction of ovulation.

the body temperature rises slightly when you ovulate.

There are ovulation sticks that predict/detect LH surge.
ovulation occurs 12-24 hours after the detection of urine LH surge.

Question 21

How does home ovulation methods work?

Answer 21

Home ovulation methods depend on the detection of these hormones in urine or saliva, or the change in other body fluid such as cervical mucus in the vagina.

Urine LH surge detection is the simplest and cheapest.

Question 22

what is the first polar body?

Answer 22

the first polar body is where half the chromosome is stored while the oocyte becomes the secondary oocyte.

the oocyte begins the 2nd meiotic division but arrests again.

Question 23

how long does the oocyte stay in the uterine tube?

Answer 23

2-3 days

Question 24

What happens after ovulation to the CL?

Answer 24

The follicle collapses and forms the CL. It produces progesterone as well as E2. it contains LHr so its growth is supported by LH and hCG.

Question 25

what does the CL do in the event of a pregnancy?

Answer 25

It supports the embryo until the placenta is established, and the hCG support the corpus luteum.

Question 26

how does progesterone support the oocyte?

Answer 26

It prepares the endometrium, it controls cells in the fallopian tube, It alters secretions of the cervix.

Question 27

how does oestradiol support the oocyte?

Answer 27

It supports the endometrium.

Question 28

what happens if pregnancy does not occur?

Answer 28

negative feedback of LH leads to the death of CL on the 14th day. Removal of CL occurs to help start a new cycle.

Cell death occurs, vasculature breakdown and the CL shrink.