WALT ; Describe how the menstrual cycle works All can identify the 4 hormones involved. Most can describe how they regulate the menstrual cycle Some can.

WALT ; Describe how the menstrual cycle works

All can identify the 4 hormones involved.

Most can describe how they regulate the menstrual cycle

Some can explain how the negative feedback mechanism controls the menstrual cycle

The menstrual cycle?

Fertility

3 hormones are involved in the menstrual cycle: oestrogen, LH and FSH. Here’s how:

Step 3: LH stimulates the release of the mature egg in the middle of the menstrual cycle

Artificial fertility:

1) To INCREASE fertility FSH is given to stimulate maturation of eggs.

2) To DECREASE fertility oestrogen is given (“The Pill”) to inhibit FSH production stopping eggs from maturing.

Step 1: FSH produced by the pituitary gland causes both an egg to mature and the ovaries to start producing oestrogen

Step 2: The rising levels of oestrogen cause the pituitary gland to stop producing FSH and produce LH instead

Inside the ovaryWhat happens in the ovary during the menstrual cycle?

Day 1-13:egg developing inside the growing follicle

Day 14:ovulation – egg released from follicle

Day 15-28:empty follicle turns into corpus luteum (yellow body)

immature eggs

Uterus liningThe lining of the uterus becomes thicker with blood vessels and more stable during the menstrual cycle. Why is this important?

2 106 84 12 14 16 18 20 22 24 26 28

days after start of period

ute

rus

lin

ing

thic

knes

s

period

A fertilized egg will bury itself (implant) in the uterus lining. The egg needs a plentiful supply of oxygen and nutrients to develop.

Hormone levels

PregnancyIf the egg is fertilized, the uterus lining must not break down otherwise the fertilized egg will not develop.

corpus luteum: continues to produceprogesterone and oestrogen

egg fertilized:uterus lining maintained, egg implanted

progesterone memoTo: uterusFrom: corpus luteumMaintain uterus lining.

oestrogen memoTo: pituitaryFrom: corpus luteum

Don’t send FSH.

How does the contraceptive pill work?

progesterone memoTo: pituitaryFrom: contraceptive pill

Stop sending FSH.

Contraceptive pills contain progesterone and need to be taken every day. How do they work?

no FSH received:no egg maturing

Contraceptive pills mimic pregnancy, which means that the ovaries do not produce any eggs.

Summary of fertility hormones