Menstrual Cycle

Question 1

What is the corpus luteum?

Answer 1

The tissue in the ovary that forms at the site of a ruptured follicle following ovulation

Question 2

What is the Graafian follicle?

Answer 2

The first follicle to fully mature in the follicular phase. Develops into the corpus luteum.

Question 3

Where is GnRH released from?

Answer 3

Hypothalamus

Question 4

What is the role of GnRH?

Answer 4

Stimulates the anterior pituitary to release FSH and LH.

Question 5

What is the role of FSH?

Answer 5

Stimulates follicular activity promoting E2 (oestradiol) release from granulosa cellsT

Question 6

What is the role of LH?

Answer 6

Triggers ovulation
Promotes corpus luteum development
Stimulates progesterone

Question 7

Describe the negative feedbacK mechanism of the menstrual cycle

Answer 7

1. GnRH acts on anterior pituitary to stimulate FSH and LH
2. LH and FSH bind to ovaries which releases oestrogen and inhibin
3. Increased oestrogen and inhibin have a negative feedback mechanism and inhibits the production of GnRH
4. This causes a decrease in oestrogen and inhibin which triggers the cycle to begin again

Question 8

What are the three phases of the uterine cycle?

Answer 8

Proliferative phase
Secretory phase
Menstrual phase

Question 9

Describe the proliferative phase of the uterine cycle

Answer 9

Oestrogen stimulates repair and growth of the function endometrium

Question 10

Describe the secretory phase of the uterine cycle

Answer 10

Once ovulation has occured, the corpus luteum begins to produce progesterone
This stimulates the endometrial glands to secrete substances to prime the uterus for implantation

Question 11

Describe the menstrual phase of the uterine cycle

Answer 11

If there is no implantation, the corpus luteum degenerates
The progesterone levels fall, causing the spiral arteries to contract.
This causes the functional endometrium to become ischaemic and necrotic.

Question 12

What are the phases of menstruation?

Answer 12

Follicular phase

Luteal phase

Question 13

Describe the follicular phase of menstruation

Answer 13

1. A fall in progesterone causes an increase in FSH which stimulates the follicles.
2. The Graafian follicle develops and produces oestrogen to inhibit other eggs maturing.
3. This oestrogen also thickens the endometrium and thins the cervical mucus, as well as inhibiting LH.
4. As oestrogen levels spike, conversely causes an increase in LH at day 12.
5. This causes the Graafian follicle to rupture and the oocyte is released.
6. The oocyte matures into an ovum and is released into the peritoneal space, to be taken up by the fimbriae.

Question 14

Describe the luteal phase

Answer 14

1. The empty Graafian follicle matures into the corpus luteum, stimulated by FSH and LH
2. The corpus luteum produces progesterone which primes the endometrium for implantation.
3. High levels of progetserone also cause negative feedback on LH and FSH and an increase in basal body temperature
4. The decrease in FSH and LH cause the corpus luteum to degenerate
5. Progesterone levels fall, which triggers menstruation and the cycle repeats.

Question 15

Describe the hormonal process which occur with fertilisation

Answer 15

1. hCG is produced by the fertilised ovum
2. This prevents the corpus luteum degrading
3. Progesterone continues to be produced, preventing menstruation
4. The placenta takes over the role of the corpus luteum from 8wks gestation

Question 16

In an extended cycle, which phase of menstraution differrs.

Answer 16

The follicular phase

Question 17

Describe the cervical mucus at ovulation

Answer 17

Spinnbarkeit - thin and runny to facilitate sperm access

Question 18

Describe the cervical mucus in the luteal phase

Answer 18

Tenacious and inelastic to prevent microbial invasion and protect the foetus (mucus plug formation)

Question 19

How is PMS treated?

Answer 19

First line: analgesia and advice
Then: COCP
Then: SSRI in luteal phase