Uterine Cycle

The early proliferative phase of the uterine cycle begins at the end of menstrual flow. The uterine glands in this phase are sparse and relatively small, and the epithelial cells develop microvilli and cilia under the influence of estrogen. The late proliferative phase reveals an increased thickness of the stratum functionalis, and the glands are more coiled and densely packed. The secretory phase of the uterine cycle begins at ovulation. In this phase, the glands become even more complexly coiled and the endometrial lining reaches its maximal thickness, whereas the stratum basalis and myometrium remain relatively unchanged. Note the saw-toothed appearance of the glands. Secretions rich in glycogen and glycoprotein can be observed in the lumina of the glands. If fertilization does not occur, the placental tissue does not produce hCG and the corpus luteum degenerates. The uterine lining does not receive the progesterone, causing the spiral arteries constrict and the endometrial tissue to become ischemic. This causes cell death and the sloughing of the stratum functionalis. Which hormone governs the construction of the glandular uterine lining during the proliferative phase, and where is it produced?