HISTOLOGY

1. Female Reproductive System I

2. Female reproductive system
 Ovaries
 Oviducts
 Uterus
 Vagina
 External genitalia

3. Ovary (female sex gland, female gonad)
 Functions
- female gamete production – ovogenesis
- female sex hormone secretion
⇓
estrogens
progesterone

4. Ovary is almond-shaped organ
 is enclosed by the tunica albuginea
 is covered with the germinal epithelium
⇓

5. Ovary is subdivided into the cortex and medulla
 Cortex
⇓
- developing ovarian follicles
- atretic follicles and atretic bodies
- corpus luteum and corpus albicans
 Medulla
⇓
- loose connective tissue
- blood vessels and lymphatics
- nerves

6. Ovarian cortex contains ovarian follicles
 Ovarian follicles include developing female germ cells

7. Ovogenesis is a process of the ovum development
 Includes 3 stages
- stage of proliferation
- stage of growth
- stage of maturation

8. Ovogenesis stage of proliferation
 is represented by oogonia (2n, 2c) proliferating by mitotic divisions
⇑
oogonia in the embryonic ovary

9. Oogonium proliferation occurs only in the fetal period
 oogonia are converted to the primary oocytes before birth
⇔

10. Ovogenesis stage of growth
 is represented by primary oocytes (2n, 4c)
 is subdivided into
- small growth
- large growth

11. Small growth begins in the embryogenesis
 primary oocytes enter the prophase
of the first meiotic division
 prophase does not complete until puberty
 oocytes remain in suspended prophase
called the dictyotene for several years

12. Large growth begins at puberty
 lasts for two weeks until before ovulation
 oocytes considerably enlarge in size
⇓
from 30µm to 150 µm
 oocytes synthesize and accumulate
⇓
- organelles
- cortical granules
- yolk granules
⇒

13. Large growth is accompanied by folliculogenesis
⇒
⇒

14. 0vogenesis stage of maturation includes meiosis
 primary oocyte (2n, 4c)
⇓
1st
meiotic division
⇓
 secondary oocyte (n, 2c)
⇓
2nd
meiotic division
⇓
 ootida (n, c)

15. First meiotic division completes before ovulation
 second meiotic division
⇓
- begins at ovulation
- is arrested at metaphase
- is completed in fertilization

16. Female meiotic division is unequal
 only one cell receives almost all the cytoplasm
 polar bodies receive minimal cytoplasm and are nonfunctional cells

17. Ovarian follicle
 is the oocyte surrounded by envelopes
 provides the microenvironment for developing oocyte

18. Folliculogenesis
 Includes stages
⇓
- primordial follicle
- primary follicle
- secondary follicle
- tertiary follicle

19. Primordial follicle
 Consists of
- primary oocyte in the small growth
- a single layer of flat follicular cells

20. Primordial follicle primary oocyte
 is arrested in the meiotic dictyotene
 measures about 30 µm in diameter

21. Primordial follicles predominate in the ovary
 are located in the cortex periphery just beneath the tunica albuginea
⇒

22. Primary follicle
 Consists of
- primary oocyte
- zona pellucida
- a single layer of cuboidal follicular cells

23. Primary follicle oocyte
 Primary oocyte
- enters the large growth
- becomes 50 to 80 µm in diameter
⇔

24. Zona pellucida
 is homogeneous acidophilic gel-like layer
 consists of glycosaminoglycans and glycoproteins
 is secreted by oocyte and follicular cells
⇔

25. Secondary (growing) follicle
 Consists of
- primary oocyte in the large growth
- zona pellucida
- several layers of follicular cells
- connective tissue theca folliculi
⇔

26. Membrana granulosa or stratum granulosum
 is stratified follicular epithelium
 follicular cells are identified as the granulosa cells

27. Stratum granulosum results from cell proliferation
estrogens stimulate granulosa cell proliferation
⇒

28. Follicular fluid or liquor folliculi
 appears when the stratum granulosum reaches
a thickness of 6 to 12-cell layers
 is secreted by the granulosa cells
FSH stimulates fluid secretion

29. Secondary antral follicles
 fluid-containing cavities coalesce forming the antrum
⇔

30. Granulosa cell endocrine function
 Granulosa cells
- convert androgens to estrogens under
FSH stimulation
- release estrogens to fluid and blood

31. Theca folliculi
 Is subdivided into
- theca interna – loose connective tissue
- theca externa – more dense connective tissue

32. Theca interna
 Contains
- rich network of small vessels
- theca cells
⇔
⇑
theca cells arise from mesenchyme

33. Theca cells are typically steroid-producing cells
 Are rich in
- sER
- Golgi apparatus
- vesicular mitochondria
- lipid droplets
⇒
LH
stimulates cell activity

34. Theca cells produce androgens under LH stimulation
 Androgens
are transported to the stratum granulosum
 Granulosa cells
- convert androgens into estrogens
- release estrogens into the fluid and blood
⇑
⇑

35. Growing follicles are estrogen-producing structures
 Estrogen blood level ⇒
- increases as the follicles grow
- attains the maximal size before ovulation

36. Hormonal regulation of ovarian follicle endocrine function
 LH stimulates the theca cells
- to produce androgens
 FSH stimulates the granulosa cells
- to convert androgens to estrogens
- to release estrogens into the blood
 Estrogens through feed-back loop
- inhibit FSH release
- activate LH production

37. Tertiary follicle (mature follicle or Graafian vesicle)
 represents the final stage of folliculogenesis
 is preovulatory follicle
 measures 10 mm and more in diameter
 extends through the full cortex thickness
 bulges on the ovarian surface

38. Tertiary follicle oocyte
 reaches its final size – about 150 µm in diameter
 resumes the first meiotic division
 becomes secondary oocyte

39. Tertiary follicle oocyte is acentrically positioned
 on the cumulus oophorus
 is surrounded by envelopes
- zona pellucida
- corona radiata
cumulus oophorus ⇑

40. Tertiary follicle envelopes
 Stratum granulosum
- becomes thin
- forms the cumulus oophorus
 Antrum
- increases in size
 Theca folliculi
- is more prominent

41. Ovulation
 is the release of the secondary oocyte
with zona pellucida and corona radiata
from the Graafian follicle ⇒
 occurs on the 14th
day of the large growth

42. Ovulating oocyte
 begins the second meiotic division
 progresses only to the metaphase
 division is arrested at the metaphase II
 secondary oocyte at the metaphase II
leaves the ovary in ovulation ⇒

43. Stigma formation
 Stigma ruptures, forming a small gap in
- germinal epithelium
- ovarian capsule
- wall of the Graafian follicle
⇓
secondary oocyte with envelopes leaves the ovary

44. Ovulation mechanisms
 follicular fluid increases in volume and pressure
 proteolytic enzymes
- lyse the stigma and follicular wall
- separate the oocyte-cumulus complex
 theca externa myofibroblasts contract
the oocyte leaves the ovary ⇒

45. Ovulation is hormonal-mediated process
 is induced by the gonadotropin maximal
blood concentration ⇒
⇓
LH peak (surge) – 12 hours before ovulation
FSH peak (surge) – 36 hours before ovulation

46. Ovulated oocyte enters the oviduct
 Oviduct infundibulum fimbriae
 cover the ovarian surface
 direct the oocyte into the oviduct
 prevent it to enter the peritoneal cavity

47. Corpus luteum or yellow body
 develops in the place of collapsed follicle
after ovulation

48. Bleeding from the capillaries into the follicular lumen
 leads to the corpus hemorrhagicum formation with a central clot
 connective tissue invades the former follicular cavity
⇔

49. Corpus luteum formation – luteinization
 Stages of
 vascularization and proliferation
 glandular metamorphosis
 secretion
 involution

50. Stage of vascularization and proliferation
 granulosa basement membrane is destroyed
 capillaries enter the stratum granulosum and form a rich vascular network
 granulosa cells and theca cells proliferate

51. Stage of glandular metamorphosis
 granulosa cells and theca-cells differentiate and become the lutein cells
 increase in size and accumulate
- sER
- mitochondria with vesicular cristae
- Golgi apparatus
- lipid droplets
- pigment lipochrome
 lipochrome imparts to lutein cells a yellow appearance in fresh preparation

52. Granulosa lutein cells
 are derived from the granulosa cells
 are pale and large – 30 µm in diameter
 are centrally located
⇔

53. Theca lutein cells
 are derived from the theca-cells
 are darker and smaller – 15 µm in diameter
 are peripherally located
⇔

54. Corpus luteum development
 lasts from 2 to 3 days after ovulation
 is controlled by LH

55. Stage of secretion
 Corpus luteum secretes progesterone
⇓
- prepares female organs (the endometrium, mammary glands) for pregnancy
- inhibits ovarian follicle development
 secretion is regulated by LTH (prolactin)

56. Corpus luteum types
 Corpus luteum of pregnancy
 develops if fertilization and implantation occur
 attains a size of 2 to 3 cm
 exists about 6 months
 Corpus luteum of menstruation
 develops if fertilization do not occur
 is small in size
 exists about 12 days

57. Stage of involution occurs after pregnancy or menstruation
 lutein cells die by apoptosis
 cell remnants are phagocytosed by macrophages
 connective tissue corpus albicans is formed
⇔

58. Atresia is a process of ovarian follicle degeneration
 primordial and primary follicles degenerate and disappear,
leaving no trace of their existence

59. Atresia of secondary and tertiary follicles
 results in the atretic body formation
⇒ ⇒ ⇒
⇑

60. Stratum granulosum changes appear in the first place
 granulosa is infiltrated by neutrophils and macrophages
 granulosa cells are sloughed into the antrum
 connective tissue and blood vessels invade
the granulosa and antrum

61. Oocyte degeneration occurs for the second time
 oocyte undergoes apoptosis
 zona pellucida becomes folded and is broken down
 their remnants are phagocytozed by macrophages

62. Theca-cells proliferate and differentiate
 become the atretic body cells
 produce steroid hormones, mainly estrogens
⇔
⇑
atretic body contains rich capillary network

63. Glassy membrane is a characteristic feature of the atretic bodies
 is the former granulosa basal membrane
 separates from follicular cells
 increases in thickness and becomes folded
the glassy membrane in an atretic follicle ⇒

64. The End
Thank you for attention!