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Unformatted text preview: for the implanted zygote. Secretory Phase After ovulation, the uterus enters the secretory phase . The corpus luteum secretes progesterone, which stimulates the thickening of the stratum functionalis. This thickening is the result of increased glycogen-rich fluids secreted into the interstitial space. Premenstrual and Menstrual Phases If implantation does not occur, the corpus luteum degrades and progesterone levels decrease. Without progesterone, the arteries that supply the stratum functionalis constrict, resulting in endometrial ischemia ; without blood, the tissue dies. These events occur premenstrually . During menstruation , the necrotic endometrial tissues fall away from the wall of the uterus and accumulated fluids, blood and tissues (and the unfertilized egg) are discharged through the vagina. The menstrual fluid contains fibrinolysin, which prevents the blood from clotting....
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- Fall '10