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| Hormonal Control of Cyclic Changes in Ovaries and Uterus During Menstrual Cycle |
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| The cyclic changes in the ovary and uterus are under the control of estrogen and progesterone hormones whose secretion is under the control of gonadotropic hormones secreted by anterior pituitary. |
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| Hormonal Control of Menstrual Cycle in Human Female |
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 During menstrual phase the levels of estrogen and progesterone falls considerably. |
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 This induces adenohypophysis to secrete FSH and LH. |
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 Increased levels of FSH stimulates the graafian follicle to mature and secrete estrogens. The rising level of estrogen, causes the endometrium to become thicker and more richly supplied with blood vessels. The level of estrogens in blood increases gradually for a few days and is at the peak on the 12th day of the cycle. |
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 The estrogen surge reduces FSH secretion and this in turn introduces LH surge within 12 hours i.e., on the 13th day of the cycle. |
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 LH causes ovulation and formation of corpus luteum. |
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 During post ovulatory phase corpus luteum secretes progesterone. |
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 Corpus luteum secretes progesterone, which performs the following functions: |
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| a) It facilitates the preparation of the endometrium of the uterus for receiving the blastocyst and its implantation. (whether fertilisation occurs or not) |
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| b) It inhibits the contraction of the uterus and any further development of a new follicle. |
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| c) If fertilisation does not occur, the rising progesterone level inhibits the release of Gonadotropin releasing hormone (GnRH), which inturn inhibits the production of FSH, LH and progesterone. |
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| d) Once the progesterone level drops, the corpus luteum begins to degenerate resulting in its transformation into a white body called the corpus albicans. |
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| e) These hormonal changes, further, cause the breakdown of the endometrium, inhibition of uterine contraction ceases and the menstrual bleeding begins. |
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 The low level of estrogens and progesterone stimulates secretion of FSH and LH from anterior pituitary initiating the next ovarian cycle. |
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| If fertilisation occurs, corpus luteum persists and secretes progesterone and estrogens during pregnancy. Fertilised egg starts developing and simultaneously travels down and gets implanted in the uterus. Ovarian cycle comes to a temporary halt. |
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| Most mammals are seasonal breeders. The female becomes sexually responsive only in a particular season. This period of sexual responsiveness in female is called Oestrous Cycle or heat period. It is followed by anaestrous or quiescence during which the female does not copulate with male. |
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| Example: Breeding season is autumn for sheep and spring and autumn for bitches. |
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