1. The Menstrual Cycle

2.  Releasing of one egg (ovulation) every month from the ovaries  4 steps: Preparing the egg Releasing egg Preparing the endometrium Shedding endometrium if egg is not fertilized  Takes about 28 days

3. There are four principal hormones involved in the control of the human menstrual cycle FSH – Follicle Stimulating Hormone – secreted into the blood from the pituitary gland LH – Luteinising Hormone – secreted into the blood from the pituitary gland OESTROGEN – secreted by the developing follicles (ball of cells around ova) in the ovary PROGESTERONE – secreted by the yellow body (corpus luteum) in the ovary Hormonal Control of the Menstrual Cycle Pre-Ovulation Hormones Post-Ovulation Hormones

4. Hormones of the Pituitary Gland Anterior lobe of the pituitary gland Hypothalamus FSH – Follicle Stimulating Hormone LH – Luteinising Hormone

5. Follicle Stimulating Hormone = FSH  Causes follicles (ball of cells that help develop ova) to develop in the ovary.  Stimulates follicular cells of the ovary to secrete oestrogen & small amounts of progesterone.

6. Luteinising Hormone = LH  Causes ovulation  Causes a follicle after ovulation to develop into a Yellow body (corpus luteum) which produces oestrogen and progesterone.

7. FSH LH oestrogens 28 Day Cycle: 1-5: Menstruation; endometrium is shed FSH increases 6-12: Follicles develop and oestrogen increases 12-14: Oestrogen at peak; LH and FSH spike 14: Ovulation

8. FSH LH oestrogens progesterone 28 Day Cycle: 14-25: LH causes follicle to change to yellow body (corpus luteum) which raises progesterone levels Endometrium thickens and FSH inhibited

9. FSH LH oestrogens progesterone 28 Day Cycle: No feritilization  25-28: High progesterone levels inhibit LH (negative feedback) Yellow body (corpus luteum) degrades so progesterone drops FSH increases and endometrium is lost ( menstruation )

10. Endometrial Changes  The events occurring in the ovary during the menstrual cycle are accompanied by changes in the endometrial lining of the uterus Endometrium is being shed during menstruation Oestrogen secreted by the developing follicles repairs the endometrium Progesterone thickens the endometrium Progesterone stimulates glands in the endometrium to increase in size Spiral arteries

11. FSH LH oestrogens progesterone 28 Day Cycle: Fertilization  Endometrium stays due to progesterone from yellow body Placenta forms and keeps oestrogen levels high LH is inhibited so ovulation does not start again

12. Implantation