Start of cycle

FSH levels rise

Lining of uterus (endometrium) breaks down (due to low levels of progesterone and estrogen)

FSH causes follicles to developand estrogen to be secreted by follicle which causes moreFSH to be released

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Estrogen stimulates repair of the endometrium

Rising estrogen levels cause an LH surge

LH surge causes ovulation

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High LH causes less estrogen to be secreted(an example of negative feedback)

After ovulation follicle develops into the corpus luteum which secretes progesterone which maintain the endometrium

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High levels of progesterone inhibit FSH and LH secretion (negative feedback)

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If no embryo is formed the corpus luteum breaks down then progesterone and estrogen levels fall and endometrium will break down

Low levels of progesterone and estrogen allow levels of FSH to rise

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