1. Oogenesis is the process of ovum development (process of female gamete production). The first gametes are formed during embryonic life. The primordial germ cells ingress from the yolk sac and migrate to the medial border of the urogenital ridge. The primordial germ cells (oogonia) will divide into primary oocytes and will then stop in the diplotene stage of Meiosis 1 until puberty. Puberty is initiated by a surge in the gonadotropic hormones from the pituitary. After puberty, FSH will be released and will throw a few primary oocytes (contained within a layer of follicular cells, collectively known as a primordial follicle) into further development. The primordial follicle will do the majority of the changing during the next phase of development. The follicular layer will grow and develop, changing the primordial to a primary (unilaminar then multilaminar) to a secondary follicle and then finally to a mature follicle. A surge in LH (caused by increased estrogen levels in the blood from the granulosal/follicular cells)will cause the mature follicle to ovulate and only then will the primary oocyte complete meiosis 1 and become a secondary oocyte. Until this point, the developing egg was diploid. At this point in the story, the egg has gone through mitosis, meiosis 1 and is therefore haploid with replicated chromosomes. The egg is surrounded by a zona pelucida and a corona radiata, the latter of which is derived from the follicular cells of the ovary. The egg (secondary oocyte) will stay in this state until it is fertilized. When/if a fertilization event occurs, the secondary oocyte will complete meiosis 2 and become an ootid (only for a short time, as fertilzation is eminent and it will soon be a zygote).
  2. Before ovulation, the egg is diploid (primary oocyte). After ovulation prior to fertilization, the egg is haploid (secondary oocyte). After fertilization, the egg is haploid and has separated sister chromatids (ootid).
  3. The ovary from the outside in.
  4. Germinal epithelium-simple cuboidal sheet continuous with the peritoneum.
  5. Tunica albuginea—connective tissue sheath
  6. Beneath the tunica abluginea are the stromal cells
  7. Cortex—contains developing follicles
  8. Medulla—Contains blood vessels
  9. Graffian Follicles are mature follicles and bulge out of the ovary. The granulosal cells secrete estrogen, which at high levels causes a surge in LH and a decrease in FSH secretion (ovulation from LH, stops further development of other follicles). The estrogen also controls the proliferative phase of endometrial development. Once the egg is ovulated the remaining follicle will become the corpus luteum. The granulosal contribution to he CL will secrete progesterone and convert the androgens produced by the the theca luteum cells. The theca luteum cell are derived from the theca interna and secrete progesterone and other androgens. Progesterone from the CL will cause a decrease in LH production which will cause the CL to start to degenerate. Decreased progesterone will cause the contracture of the coiled arteries, causing cramps and menstruation. This decrease in LH will also allow for production of FSH which will start the next cycle.