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What happens to the endometrium during the secretory phase?
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menstruation
Cyclical changes during a woman's normal ovulatory menstrual cycle.
During the secretory phase of the menstrual cycle, the endometrium undergoes significant changes to prepare for the potential implantation of a fertilized ovum.21
Following ovulation, the corpus luteum secretes large quantities of progesterone, which induces the following transformations in the uterine lining:
- Glandular activity: The endometrial glands become distended with secretion and highly tortuous.1
- Structural changes: The stromal cells become swollen, and the tissue increases in thickness.21
- Vascularity: There is an increase in blood supply and water content within the uterine wall.3
- Nutrient preparation: The endometrium increases its secretion of glycogen, which serves as a vital nutrient for the developing egg.3
These changes create a receptive environment for a blastocyst. If fertilization does not occur, the corpus luteum degenerates, leading to a drop in hormone levels, which causes the endometrial blood vessels to constrict and the lining to be shed during menstruation.241