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
Fertility 3 hormonesare involved in the menstrual cycle: oestrogen, LH and FSH. Here’s how: Step 1: FSH produced by the pituitary gland causes both an egg to mature and the ovaries to start producing oestrogen Step 3: LH stimulates the release of the mature egg in the middle of the menstrual cycle Step 2: The rising levels of oestrogen cause the pituitary gland to stop producing FSH and produce LH instead • Artificial fertility: • To INCREASE fertility FSH is given to stimulate maturation of eggs. • To DECREASE fertility oestrogen is given (“The Pill”) to inhibit FSH production stopping eggs from maturing.
Day 15-28:empty follicle turns into corpus luteum (yellow body) immature eggs Day 1-13: egg developing inside the growing follicle Day 14:ovulation – egg released from follicle Inside the ovary What happens in the ovary during the menstrual cycle?
period uterus liningthickness days after start of period 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Uterus lining The lining of the uterus becomes thicker with blood vessels and more stable during the menstrual cycle. Why is this important? A fertilized egg will bury itself (implant) in the uterus lining. The egg needs a plentiful supply of oxygen and nutrients to develop.
progesterone memo To: uterus From: corpus luteum Maintain uterus lining. egg fertilized: uterus lining maintained, egg implanted oestrogen memo To: pituitary From: corpus luteum Don’t send FSH. corpus luteum: continues to produce progesterone and oestrogen Pregnancy If the egg is fertilized, the uterus lining must not break down otherwise the fertilized egg will not develop.
How does the contraceptive pill work? progesterone memo To: pituitary From: contraceptive pill Stop sending FSH. no FSH received: no egg maturing Contraceptive pills contain progesterone and need to be taken every day. How do they work? Contraceptive pills mimic pregnancy, which means that the ovaries do not produce any eggs.