1. Hormonal control of the menstrual cycle

2. Overview of human female reproductive cycle

3. Answers

4. Side view of female reproductive system

5. General information
The ovaries are organs that are responsible for the development of female gametes.
At birth around cells are present which are immature
Each month after puberty, one of these cells completes its development into an ovum.

6. Menstrual Cycle Animations
Clearblue - Menstrual Cycle

8. Hormonal Control of the Human Female Menstrual Cycle
The oestrus cycle lasts approximately 28 days in Humans
It is controlled by the interaction of four main hormones:
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Oestrogen
Progesterone
These hormones interact in different ways

9. FSH Immature ova are encased in a follicle
The pituitary gland secretes Follicle Stimulating Hormone (FSH) which causes the follicle cells surrounding one (or more) immature ova to grow and divide
This leads to the development of a mature ovum in the follicle and this secretes oestrogen

10. Oestrogen Oestrogen has many functions:
Stimulates growth of the lining of the uterus
This occurs on days 5 – 14
Low levels of oestrogen begins to inhibit FSH secretion by pituitary gland (so no other follicles begin to mature)
As the level of oestrogen becomes higher, it stimulates the pituitary gland to secrete another hormone, Luteinising Hormone (LH)
This occurs on day 10
It also stimulates the pituitary to produce FSH again.

11. LH
The developing follicle continues to secrete oestrogen which continues to stimulate FSH & LH secretion from the pituitary gland.
When the level of oestrogen is high enough, it triggers a surge of LH which causes ovulation
The mature follicle bursts and the mature ovum passes down the fallopian tube (oviduct) towards the uterus where fertilisation can occur
This occurs on day 14

12. Progesterone
After ovulation, the empty follicle does not disappear but forms a new structure called the corpus luteum
The corpus luteum secretes some oestrogen but secretes a lot of another hormone: Progesterone
Progesterone:
Inhibits LH and FSH from the pituitary gland
Continues to stimulate growth of the lining of the uterus and maintains its thickness
This occurs on days 14 – 28

13. Menstruation
If the egg does not become fertilised, the corpus luteum degenerates causing the lining of the uterus to be shed
This is known as menstruation
This occurs on days 1 – 5.

14. Pregnancy
If the ovum becomes fertilised, pregnancy occurs, and the fertilised ovum implants in the uterus wall.
This thick uterus lining must be maintained and it eventually becomes thicker and forms the placenta.
This is under the control of another hormone, (HCG) which is produced following implantation.
We will come back to pregnancy later!

15. Hormone levels and changes

16. Ovary with the stages of development of the ovum during an ovarian cycle.
i) Chose different colours and colour in:
The cells that produce oestrogen.
The structure that produces progesterone.
All the ova.
ii) In the space provided, give the name of "event A’ on the diagram

17. Answers

18. Task: Summary of hormones
Secreted by
Target organ
Function
FSH
Oestrogen LH
Progesterone

19. Summary of hormones Hormone Secreted by Target organ Function FSH
Pituitary gland
Ovary
Stimulates development of a follicle
Oestrogen
Ovary /ovarian follicle & corpus luteum (small amount)
Uterus lining
Pituitary Gland
Stimulates LH secretion at high concentrations
Stimulates development of endometrium
Inhibits FSH secretion at low concentrations/stimulates it a high concentrations LH
Empty follicle
Stimulates ovulation following oestrogen induced LH surge
Stimulates development of corpus luteum
Progesterone
Corpus Luteum
Stimulates & maintains lining of uterus
Inhibits FSH & LH