A nurse is teaching a woman about her menstrual cycle. The nurse states that __________ is the most important change that happens during the secretory phase of the menstrual cycle.

During the secretory phase of the menstrual cycle, the most critical change that occurs is the proliferation of the endometrium. This phase follows ovulation and is primarily driven by the hormone progesterone, which is secreted by the corpus luteum. The purpose of this phase is to prepare the endometrium for potential implantation of a fertilized egg.

During this time, the endometrial lining thickens and becomes enriched with nutrients and blood vessels, creating a supportive environment for an embryo if fertilization occurs. If implantation does not happen, the corpus luteum degenerates, leading to a decrease in progesterone levels, which ultimately triggers the menstruation phase.

In contrast, maturation of the graafian follicle occurs in the follicular phase before ovulation and is not specific to the secretory phase. Multiplication of the fimbriae is not a physiological event that takes place during the menstrual cycle, as fimbriae are parts of the fallopian tubes and their function does not change cyclically in this context. Secretion of human chorionic gonadotropin (hCG) is primarily relevant after fertilization has occurred, as it is produced by the placenta to maintain the corpus luteum rather than being a direct feature of the