Female Reproductive: Ovary

  1. Ovary
    • sits in the pelvic cavity
    • covered by a visceral peritoneum (mesothelium, cuboidal cells)
    • deep to the epithelium is a dense CT capsule called the Tunica Albuginea
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    • deep to that is the outer cortex which will contain follicles at different stages
    • within the follicles are primary or 2ndary oocytes & supporting cells
    • the medulla doesn't contain any type of follicles, just has stroma & BVs (esp. a highly coiled artery)
  2. Where do most ovarian tumors arise?
    • mesothelial covering, aka the visceral peritoneum
    • it's the site of 70% of ovarian tumors
  3. Ovarian Cortex
    • can see lots of follicles at many different stages
    • most peripheral: primordial follicles
    • as they develop they move inward
    • most will die, only 1 will fully mature
  4. Follicle Cycle
    • have 6-700,000 primordial follicles at birth
    • each month a few will begin to develop into primary follicles 
    • when primary follicles develop an antrum (space), they're called Vesicular follicles
    • mature Vesicular follicles are called Graffian follicles (larger antrum)
    • following ovulation, what's left of the follicle becomes a corpus luteum of menstruation or pregnancy
  5. Primordial Follicle
    • the earliest stage of follicle development
    • each contains a primary oöcyte surrounded by one layer of squamous follicular (granulosa) cells resting inside a thin basal lamina
    • the internal primary oöcyte has a large, vesicular nucleus w/ a large nucleolus
    • it's arrested in the diplotene stage of prophase of meiosis I
    • this means it contains duplicated chromosomes (4n DNA)
    • crossing-over has already occurred, meaning genetic sequences differ from parent
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  6. Why isn't a primordial follicle considered foreign?
    • even though the gametes are “foreign” because they have different DNA than the parent cells, this event occurs prior to development of immunocompetence
    • therefore gametes are not attacked by the host immune system, they're considered "self" & don't need to be kept separate from the blood supply (unlike in testes)
  7. Weird Things in Primordial Follicles
    • Balbiani Body: collection of golgi membranes in the oocyte; will disperse later
    • Annluate Lamellae: stacks of nuclear membrane (darkenings = nuclear pores); role in oocyte development = unclear
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  8. Primary (Early) Follicles
    • starting at puberty & at the beginning of every future menstrual cycle chosen follicles (aka those with the most FSH receptors on their surface) begin to mature
    • 1st thing to change is that the flattened follicular (granulosa) cells around the oocyte become cuboidal
    • this characterizes a unilaminar primary follicle
    • follicular cells still sit on a basal lamina
    • zona pellucida starts to develop between the follicular cells & oocyte
    • these oocytes/follicles becomes larger (esp. in comparison to primordial follicles)
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  9. Primary (Late, Multilaminar) Follicles
    • cuboidal follicular cells have now proliferated, called granulosa cells (these may represent a pseudostratified epithelium but look like several layers of follicular cells)
    • has a thicker zona pellucida
    • oocyte is larger 
    • cellular stroma immediately around the follicle differentiates into theca cells
    • follicle & oocyte are still enclosed by a complete basal lamina separating them from the theca cells
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  10. How can granulosa cells & an oocyte communicate?
    • granulosa cells have microvilli projections that extend through the zona pellucida to the oocyte
    • the oocyte also has processes that extend through the ZP to granulosa cells
    • there are also gap junctional connections between the 2
  11. Secondary (Antral) Follicle
    • antral refers to the fact that they have a fluid filled region within the field of granulosa cells
    • that antrum will grow
    • granulosa cells exist at the periphery of the follicle, around the oocyte, & as a stalk upon which the oocytes rest
    • the oöcyte has reached its full size (0.2mm) & the follicle is ~10 mm in diameter
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  12. What causes the development of the antrum?
    • a release of hyaluronic acid from granulosa cells
    • this is a very charged substance, so water will enter the follicle & fill the space
  13. Corona Radiata
    granulosa cells that directly surround the ooctye & separate it from the antrum
  14. Cumulus Oophorus
    • granulosa cells between the corona radiata & the circular follicle that surrounds the whole antrum
    • looks like a pedestal on which the corona radiata & oocyte sit
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  15. What does oocyte development require?
    • high concentrations of estrogen
    • this comes from granulosa cells, which also release sex steroid binding globulin (androgen binding protein) to concentrate estrogen in the follicle
    • estrogen levels can be >100X higher in the follicle than in the blood
  16. Can the Granulosa Cells produce estrogens directly?
    • no, they do not have the capacity to do so
    • Aromatase converts androgens secreted by Theca Interna cells to estrogens for faster oocyte growth
  17. How do nutrients get to the oocyte?
    • because there are no blood vessels to the oocyte, nutrients must diffuse through the outer basal lamina through granulosa cells to the oocyte
    • it's a long distance, but nutrient transfer is facilitated by:
    • 1. gap junctions between granulosa cells & the oocyte
    • 2. long cytoplasmic processes from the oocyte that invaginate & touch granulosa cells through the zona pellucida
  18. Theca Folliculi
    • 2 layers of theca cells surrounding the granulosa cells (separated by the basal lamina)
    • Interna: has abundant SER + lipid droplets (steroid producing cells making androgens)
    • Externa: CT-like (become myofibroblasts)
    • BOTH layers are vascularized
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  19. Theca Interna Cells
    • express receptors for LH
    • when signaled they synthesize androstenedione & testosterone
    • these androgens diffuse into the follicle's granulosa cells where FSH has stimulated the synthesis of aromatase
    • (converts androgens → estradiol & estrone)
  20. What role do estrogens play outside of the ovary?
    they stimulate endometrial gland proliferation (in the uterus) & mid-cycle, the LH surge
  21. Theca Externa
    • cells will differentiate into      myofibroblast-like cells that are LH responsive
    • these contract during ovulation, which occurs in response to the LH surge
  22. Mature (Graäfian) Follicle
    • follicle has reached its largest size (2.5 cm) & can be observed by ultrasound (during IVF)
    • immediately before ovulation the antrum increases greatly in size
    • even the corona radiata starts filling with fluid, which separates the oocyte + corona radiata in preparation for ovulation
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  23. When does the oocyte progress from prophase of meiosis I to metaphase of meiosis II?
    • "sometime between being a Secondary (Antral) Follicle & Mature (Graäfian) Follicle" 
    • an oocyte in a Mature Follicle is arrested in metaphase of meiosis II & will only complete meiosis if fertilized by a sperm
    • all oocytes in any follicle prior to a mature one = primary (4n)
    • an oocyte in a mature follicle = secondary (2n - haploid)
  24. Ovulation
    • occurs shortly after a mid-menstrual cycle LH surge from the Anterior Pituitary
    • causes contraction of theca      externa myofibroblasts which expel the secondary oocyte, ZP, & intact corona radiata
    • the released oocyte is captured by the oviduct (fallopian tube)
  25. What is thought to arise from constant rupture & repair of the mesothelium (visceral peritoneum)?
    epithelial tumor development
  26. Corpus Luteum
    • what's left of the follicle becomes a corpus luteum after ovulation
    • the basement membrane (between granulosa cells & stroma) breaks down
    • this allows an ingrowth of BVs
    • there's a proliferation of both granulosa & theca interna cells
    • it becomes a highly vascularized endocrine body whose granulosa cells produce Progesterone to support a possible fertilization event & pregnancy
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  27. Corpus Luteum Cell Types
    • both make Progesterone
    • Granulosa Lutein Cells: paler, larger
    • Theca Lutein Cells: are smaller & darker than granulosa LCs (& more tightly packed together); again make androgens (androstenedione) for conversion to estrogens
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  28. How long will a Corpus Luteum persist during pregnancy & why?
    • ~6 months, due to placental chorionic gonadotropin
    • the continuous CL progesterone secretion maintains the uterine lining
  29. Corpus Albicans ('white body')
    • all corpus luteum (from a menstrual cycle & pregnancy) will eventually degenerate & be replaced by a dense collagenous CT scar called corpus albicans
    • after ~10 days of life for a corpus luteum, it begins to degenerate & progesterone levels fall with this degeneration
    • the scar is larger for a corpus luteum of pregnancy than that of a corpus luteum of menstruation
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    • contains few cells, appears 'cloud-like'
  30. Follicular Atresia
    • death & resorption of the follicle
    • can occur at any stage of folliculogenesis (primordial → mature)
    • 98% of follicles (most) will become atretic
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    • can see granulosa cells breaking up
    • lots of cell death (apoptosis)
    • remnant is the “glassy membrane (former basement membrane)
  31. Glassy Membrane
    • a thick structure made of the basal lamina between the granulosa cells & theca cells that persists after follicular atresia
    • some of the thecal cells from atretic follicles may remain & become interstitial cells that (along with the adrenal glands) become sources of sex hormones after menopause
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    • a greatly thickening basal lamina from a former corpus luteum
  32. Uterine Tube (aka Fallopian Tube, Oviduct, Salpinx Uterina)
    • consists of 4 segments -
    • 1. Infundibulum: wide funnel-shape with fimbriae that have ciliated cells that create a 'current' to 'catch' an ovulated ovum
    • 2. Ampulla: where fertilization usually occurs; longest part; has a highly infolded mucosa
    • 3. Isthmus: short part
    • 4. Intramural: shortest; is within the uterus wall
    • salpinx = common name for tube in anatomy
  33. Uterine Tube Functions
    • provides bi-directional transport:
    • the ovum moves toward the uterus via ciliary action & peristalsis
    • sperm move away from uterus (faster than swimming alone would allow)
    • contains secretions that stimulate sperm maturation
    • provides an environment for fertilization
  34. Ampulla
    • the outermost part facing the peritoneal cavity is lined by a serosa (aka mesothelium, visceral peritoneum)
    • then there's a muscularis, a 2-layer inner circular outer longitudinal muscle layer (expected in any organ that has peristalsis 
    • *most characteristic: highly infolded mucosa regions: longitudinal folds  (resembling fern leaves)
    • epithelium facing the lumen is made up of 2 types, simple columnar with & without cilia
    • the non-ciliated cells are called Peg Cells; they are secretory 
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  35. Peg Cells
    • secretory, so they don't have any cilia on their surface
    • any place where you see a break in basal body staining must be where there's a secretory/Peg cell
    • Peg cell secretions stimulate sperm capacitation
    • this changes sperm movement & enables sperm to bind to the ZP & fertilize the egg
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  36. Cyclical Changes that Take Place in the Ampulla
    • estrogen being produced by growing follicular granulosa cells increases ciliogenesis
    • progesterone produced from the Corpus Luteum increases the number of  secretory cells
Author
mse263
ID
325249
Card Set
Female Reproductive: Ovary
Description
Histology Exam 4
Updated