http://kidshealth.org/misc/movie/bodybasics/bodybasics_female_repro.html

The ovaries are organs that are responsible for the development of female gametes.

At birth around 300 000 cells are present which are immature

Each month after puberty, one of these cells completes its development into an ovum.

Clearblue - Menstrual Cycle

http://kidshealth.org/misc/movie/bodybasics/

bodybasics_female_repro.html

The oestrus cycle lasts approximately 28 days in Humans

It is controlled by the interaction of four main hormones: 1. Follicle stimulating hormone (FSH)2. Luteinising hormone (LH)3. Oestrogen4. Progesterone

These hormones interact in different ways

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

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.

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

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

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.

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!

i) Chose different colours and colour in:

a) The cells that produce oestrogen.

b) The structure that produces progesterone.

c) All the ova. ii) In the space

provided, give the name of "event A’ on the diagram

Hormone Secreted by Target organ Function

FSH

Oestrogen

LH

Progesterone

Hormone Secreted by Target organ Function

FSH Pituitary gland Ovary •Stimulates development of a follicle

Oestrogen Ovary /ovarian follicle & corpus luteum (small amount)

Uterus liningPituitary Gland

•Stimulates LH secretion at high concentrations•Stimulates development of endometrium•Inhibits FSH secretion at low concentrations/stimulates it a high concentrations

LH Pituitary gland OvaryEmpty follicle

•Stimulates ovulation following oestrogen induced LH surge•Stimulates development of corpus luteum

Progesterone Corpus Luteum

Uterus liningPituitary gland

•Stimulates & maintains lining of uterus•Inhibits FSH & LH