The endometrium is the inner membrane of the mammalian womb or uterus. During the menstrual cycle or estrous cycle, the endometrium grows to a thick, blood vessel-rich, glandular tissue layer. This represents an optimal environment for the implantation of a fertilised egg upon its arrival in the uterus. During this cycle the endometrium grows then breaks down and the breaking down is known as menstruation.
Overt menstruation (where there is blood flow from the vagina) occurs primarily in humans and close evolutionary relatives such as chimpanzees. Covert menstruation, where the breakdown of the endometrium occurs without vaginal discharge, appears in the estrous cycles of most placental mammals. In this case, if no fertilization takes place, the uterus reabsorbs the endometrium.
Some species, such as domestic dogs, experience small amounts of vaginal bleeding while in heat. But this discharge has a different physiological cause than menstruation.
Overt menstruation (where there is blood flow from the vagina) occurs primarily in humans and close evolutionary relatives such as chimpanzees. Covert menstruation, where the breakdown of the endometrium occurs without vaginal discharge, appears in the estrous cycles of most placental mammals. In this case, if no fertilization takes place, the uterus reabsorbs the endometrium.
Some species, such as domestic dogs, experience small amounts of vaginal bleeding while in heat. But this discharge has a different physiological cause than menstruation.
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Female animals have periods too eg. Dogs.
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No they aren't.
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No .. all mammals do.