Corpus luteum is essential for establishing and maintaining pregnancy in females. The corpus luteum secretes progesterone, which is a steroid hormone responsible for the decidualization of the endometrium (its development) and maintenance, respectively. It also produces relaxin, a hormone responsible for softening of the pubic symphysis which helps in parturition. If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 10 days in humans). It then degenerates into a corpus albicans, which is a mass of fibrous scar tissue. The uterine lining (endometrium) is expelled through the vagina (in mammals that go through a menstrual cycle).
Navicular cell navicular cells to appear in Pap smear. Navicular cell Navicular cell is a boat-shaped benign epithelial cell seen in Pap smear. They are seen in pregnancy (most prominently during smears taken in the second trimester), second half of menstrual cycle, during menopause and in women using medroxyprogesterone acetate (depo-provera) for contraception. Navicular cells have folded edges, with a thickened outer rim of cytoplasm and an eccentric nucleus. They contain abundant glycogen in the cytoplasm, giving it a central yellow halo. The cytoplasm appears golden, refractile and granular under the microscope. In depo-provera users, the high progesterone levels result in more