Why do women menstruate?
Фарингула пишет, почему женщины менструируют.
Доходчиво.
Для меня было откровением, что летучие мыши-вампиры (!!!) и прыгунчики тоже менструируют.
Жалко, что он совсем свихнулся на почве полемики с креационистами и почти перестал писать интересное.
Планирую об этом почитать-пообсуждать, потому как в рамках жарких дискуссий про Лавждоя и скрытую овуляцию это тоже важный кусочек паззла.
http://freethoughtblogs.com/pharyngula/2011/12/21/why-do-women-menstruate/
Within the mammals, there is variation in how deeply the fetus sinks its placental teeth into the uterus. Some species are epithelochorial; the connection is entirely superficial. Others are endotheliochorial, in which the placenta pierces the uterine epithelium. And others, the most invasive, are hemochorial, and actually breach maternal blood vessels. Humans are hemochorial. All of the mammalian species that menstruate are also hemochorial.
That’s a hint. Menstruation is a consequence of self-defense. Females build up that thickened uterine lining to protect and insulate themselves from the greedy embryo and its selfish placenta. In species with especially invasive embryos, it’s too late to wait for the moment of implantation - instead, they build up the wall pre-emptively, before and in case of fertilization. Then, if fertilization doesn’t occur, the universal process of responding to declining progesterone levels by sloughing off the lining occurs.
Bonus! Another process that goes on is that the lining of the uterus is also a sensor for fetal quality, detecting chromosomal abnormalities and allowing them to be spontaneously aborted early. There is some evidence for this: women vary in their degree of decidualization, and women with reduced decidualization have been found to become pregnant more often, but also exhibit pregnancy failure more often. So having a prepared uterus not only helps to fend off overly-aggressive fetuses, it allows mom a greater ability to be selective in which fetuses she carries to term.
Доходчиво.
Для меня было откровением, что летучие мыши-вампиры (!!!) и прыгунчики тоже менструируют.
Жалко, что он совсем свихнулся на почве полемики с креационистами и почти перестал писать интересное.
Планирую об этом почитать-пообсуждать, потому как в рамках жарких дискуссий про Лавждоя и скрытую овуляцию это тоже важный кусочек паззла.
http://freethoughtblogs.com/pharyngula/2011/12/21/why-do-women-menstruate/
Within the mammals, there is variation in how deeply the fetus sinks its placental teeth into the uterus. Some species are epithelochorial; the connection is entirely superficial. Others are endotheliochorial, in which the placenta pierces the uterine epithelium. And others, the most invasive, are hemochorial, and actually breach maternal blood vessels. Humans are hemochorial. All of the mammalian species that menstruate are also hemochorial.
That’s a hint. Menstruation is a consequence of self-defense. Females build up that thickened uterine lining to protect and insulate themselves from the greedy embryo and its selfish placenta. In species with especially invasive embryos, it’s too late to wait for the moment of implantation - instead, they build up the wall pre-emptively, before and in case of fertilization. Then, if fertilization doesn’t occur, the universal process of responding to declining progesterone levels by sloughing off the lining occurs.
Bonus! Another process that goes on is that the lining of the uterus is also a sensor for fetal quality, detecting chromosomal abnormalities and allowing them to be spontaneously aborted early. There is some evidence for this: women vary in their degree of decidualization, and women with reduced decidualization have been found to become pregnant more often, but also exhibit pregnancy failure more often. So having a prepared uterus not only helps to fend off overly-aggressive fetuses, it allows mom a greater ability to be selective in which fetuses she carries to term.