Updated by: Arabinda Naik
This phase usually includes cycle days 15-to-28-day cycle. The remaining cells of ovarian follicle are stimulated by the LH to produce corpus luteum (yellow body) is formed from the empty Graafian follicle and starts secreting progesterone hormone during the luteal phase. The corpus luteum secretes a large amount of progesterone. Progesterone stimulates the endometrium to produce increased amount of watery mucus. Uterine and endometrium further proliferate (about 5 mm (about 0.2 in) thick) and are ready for implantation. High levels of progesterone decrease the secretion of FSH and LH so inhibits maturation of new follicles and ovulation. During the secretory phase, there is also a similar increase in the secretion of watery mucus by the vaginal glands and by the glands of the fallopian tubes. Progesterone is also essential for maintenance and preparation of the endometrium for implantation of the embryo. An endometrium is necessary for implantation of the fertilized ovum and other events of pregnancy. In the absence of fertilization, the levels of progesterone and estrogen decrease resulting in the breakdown of endometrium and the corpus luteum degenerates and transforms into a white body called corpus albicans. This causes disintegration of the endometrium leading to menstruation making a new cycle.