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Menstrual cycle

Stage 1-Bleeding starts, uterus lining breaks down and is releases (menstruation). Also, FSH causes a follicle to mature in one of the Ovaries.

Stage 2- Lining of Uterus builds up again, from day 4 to 14, into a thick spongy layer of blood vessels ready to receive a fertilised egg. At the same time, Uterus lining build- up is being caused by Oestrogen production which stimulates LH surge when there is a high level of Oestrogen, an LH surge is stimulated.

Stage 3- An egg is released from the Ovary at day 14 (ovulation). Ovulation is stimulated by LH. The follicle ruptures and the egg is releases.

LH stimulates the remains of the follicle to develop into a Corpus Luteum-which secretes progesterone.

Stage 4- the uterus lining is maintained until day 28, when the cycle starts over if the uterus has failed to receive a fertilised egg. Meanwhile, Progesterone maintains the lining of the Uterus and inhibits FSH and LH production. When the levels of progesterone fall, and there's a low Oestrogen level, the Uterus lining breaks down. A low Progesterone level allows FSH to increase....and then the whole cycle starts again.

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