nThe menstrualphase occurs approximately
1–5of the cycle. This phase is marked by sloughing of the
functional layer and lasts through
the period of menstrual bleeding.
nThe proliferative phase follows, spanning approximately days 6–14. The initial development of the functional layer of the
endometrium overlaps the time of follicle growth and estrogen secretion.
nThe last phase is the secretory phase, which occurs at approximately days 15–28.
During the secretary phase, increased
progesterone secretion from the corpus luteum results in increased vascularization and development of uterine glands.
nIf the oocyte is not fertilized, the corpus luteum degenerates, and the progesterone level drops dramatically.
progesterone, the functional layer lining sloughs off, and the next menstrual phase begins.