1. Female reproductive system

6. Atretic follicle: Most ovarian follicles undergo atrasia, in which the follicular cells and oocytes dies and engulfed by phagocytic cells. Follicles at any stage of development may undergo atrasia and this process is characterized by: cessation of mitosis in granulose cells detachment of granulose cells from the basal lamina death of the oocytes after cell death macrophages will invade the follicle & phagocytose its debris.

7. at later stages fibroblasts will occupy the area of follicle & produce a scar of collagen called corpus fibrosum, that may persist for a long time. atrasia is most prominent after birth when the effect of maternal hormones cease & during puberty & pregnancy when marked hormonal modifications occur.

8. Ovulation: At ovulation the graffian follicle is so large that it distort the surface of the ovary, even it appear to the naked eye as a small cystic mass bulging from the ovarian surface covered by only thin layer of germinal epithelium & a very thin layer of cortical stroma. The stimulus for ovulation is a surge of LH which will also induce completion of the 1st stage of meiosis. Before ovulation the oocyte will break free from its attachment to the follicular wall & float freely in the follicular fluid surrounded by corona radiate.

9. At ovulation weakness in the wall of the follicle plus an increased follicular fluid pressure will lead to rupture of the follicle & ovulation An indication for impending ovulation is the appearance of stigma on the surface of the follicle in which the blood flow ceases resulting in local changes in color & translucence of the follicular wall. With ovulation the oocytes with its 1st polar body enclosed by the zona pellucida plus the corona radiate & some follicular fluid will leave the ovary & enter the uterine tube where it will be fertilized.

10. Ovulation occur approximately in the middle of the menstrual cycle (around the day 14 of a 28 day cycle). Usually only one oocytes is liberated with each cycle but some times no oocytes is ovulated at all (unovulatory cycle), some times 2 or more oocytes can be expelled at the same time & if they are fertilized there may be two or more fetuses. This occur mainly with the use of ovulation inducing drugs. With ovulation slight bleeding from the highly vascular theca interna occur with release of this slight amount of blood & follicular fluid into the peritoneal cavity & this is thought to be responsible for the transient mid cycle lower abdominal pain at day 14-16 experienced by some women. With ovulation slight bleeding from the highly vascular theca interna occur with release of this slight amount of blood & follicular fluid into the peritoneal cavity & this is thought to be responsible for the transient mid cycle lower abdominal pain at day 14-16 experienced by some women.

11. Corpus Luteum: After ovulation the granulose cells & the cells of the theca interna layer reorganize themselves to form a temporary endocrine organ called corpus luteum which become embedded within the cortical region. The clot filled lumen of the follicle that results from ovulation will undergo progressive organization & the blood will coagulate & then invaded by connective tissues to form the center of corpus luteum.

12. The granulose cells will increase greatly in size & they make about 80% of the parenchyma of the corpus luteum & now these cells are called granulose lutein cells these are large cells with abundant smooth endoplasmic reticulum & they are distended with lipid droplets (features characteristic for steroid secreting cells) they secret progesterone.

13. Cells of theca interna also increase in size & accumulate lipid & called theca lutein cells, these cells continue to secrete estrogen & they stain more intensely then the granulose cells. Fibrous septa partly separate the granulose lutein mass & clusters of theca lutein cells are particularly prominent in the region of these septa. At its maximum size (usually at day 20 of the cycle) the corpus luteum is an ovoid structure up to 2 cm. long & 1.5 cm. width.

14. Fate of corpus luteum: Depend whether pregnancy is established or not. The corpus luteum is programmed to act for 10-12 days after its formation. Its action is stimulated by the presence of LH. if no further hormonal stimulation occur (decrease in LH concentration) & pregnancy doesn’t occur the cells of corpus luteum start to degenerate. so there will be decrease in the granulose & theca lutein cells with the appearance of vacules on their cytoplasm, this will lead to gradual decrease in progesterone & estrogen concentration in the blood with its effect on the endometrium. if no further hormonal stimulation occur (decrease in LH concentration) & pregnancy doesn’t occur the cells of corpus luteum start to degenerate. so there will be decrease in the granulose & theca lutein cells with the appearance of vacules on their cytoplasm, this will lead to gradual decrease in progesterone & estrogen concentration in the blood with its effect on the endometrium.

15. Macrophages will phagocytose the cellular debries of the corpus luteum & near by fibroblasts will produce collagen fibers to fill the space & form a scar tissue called corpus albicans. The corpus luteim that lasts only part of the menstrual cycle & then degenerate is called Corpus luteum of menstruation.

16. If pregnancy occur: After implantation of the embryo & formation of trophoblat cells a signal to the corpus luteum is given by the human choriouic gonadotropin (secreted by the trophoblastic cells & have a similar action to LH). Thus H.C.G will rescue the corpus luteum from degeneration & further growth of corpus luteum occur with more secretion of progesterone & it is called corpus luteum of pregnancy, this structure persist for 4-5 months & then degenerate & replaced by corpus albicans. Progesterone secretion during pregnancy will: maintain the uterine mucosa through out pregnancy. stimulate secretion of uterine glands important for the nutrition of the embryo before the placenta is functional.

17. Oviduct : ( uterine tubes) Are two muscular tubes of great mobility. Each one is about 12 cm. in length & they are the site of fertilization of the ovum by spermatozoa. There are four recognizable tubal segments, each one differ in its histological features particularly in their proportion of muscle & epithelium & the degree of convolution of their epithelium.

18. These segments are: infundibulum: which is the dilated open end of the tube near the ovary with a finger like extensions called fimbriae. Ampulla: is a thin walled zone where fertilization of the ovum takes place usually. Isthmus: it is the narrower thick walled segment Intramural segment: which passes through the wall of the uterus & opens into the interior of the uterus.

19. The wall of the oviduct is formed of three layers: –Mucosa –thick muscularis layer (inner circular & outer longitudinal) –serosa composed of the visceral peritoneum

20. Mucosa of the uterine tubes: Has a longitudinal folds that are most numerous in the ampulla, these folds become smaller & less numerous in the segments of the tube that are closer to the uterus. In the intramural segment the folds are very much reduced & the internal surface is almost smooth. Microscopically: the ampulla appear to have a thin muscular wall & a large lumen with extensive mucosal folds while the isthmus appear to have a much thicker muscular wall with small lumen & less marked mucosal folds.

22. Cells of the surface epithelium: ciliated cells: particularly numerous near the ovarian end of the tube where they form about 80% of the surface epithelium but near the uterus form only about 25%. These cells are tall columnar cells, the hight of these cells & number of cilia become more prominent at time of ovulation, after that time these cells progressively shortens & loose some cilia until menstruation (this is mainly progesterone effect), & a similar changes are found through out pregnancy, while after menstruation & with the increase in estrogen level these cells increase in hight & become more ciliated.these cells are responsible for the movement of the ovum through out the tube to ward the uterine cavity. secretory cells: they produce a watery fluid which is assumed to have a nutritive function for the spermatozoa & the ovum. It will also activate the process of capacitation of the spermatozoa.