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MS 1 Unit 7 Microscopic Anatomy > Female Reproduction I > Flashcards

Female Reproduction I Flashcards

1
Q

General anatomy of ovary

A
  • two 1.5 x 3 x 1 cm almond shaped organs
  • Hilus: conduit on anterior surface for blood vessels and nerves supplying the ovary
  • suspended in the peritoneal cavity by the ovarian ligament (links to ovary medial pole to the uterus) and the mesovarium (links the ovary hilus to the board ligament)
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2
Q

Functions of ovary

A
  • generate female gametes (eggs)

- synthesize the female sex hormones estrogen and progesterone

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3
Q

General histology layers

A
  • Germinal epithelium (outer)
  • Tunica albuginea
  • Cortex
  • Medulla
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4
Q

Germinal epithelium of ovary

A
  • simple, cuboidal epithelium
  • continuous with mesothelium that lines the mesovarium, broad ligament, and peritoneal cavity
  • high regenerative capacity allows rapid healing after ovulation
  • outside layer
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5
Q

Tunica albuginea of ovary

A
  • 2nd layer (from the outside)
  • dense, irregular connective tissue
  • collagen fibers and fibroblasts
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6
Q

Cortex of ovary

A
  • -follicles- oocytes plus follicular epithelium

- stroma- highly cellular connective tissue with some smooth muscle

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7
Q

Medulla of ovary

A
  • loose connective tissue

- contains the blood and lymphatic vessels and nerves that enter at the ovary hilus

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8
Q

Ovarian Follicles

A

Functions: house germ cells (oocytes) and produce estrogen

Structure:

  • small spherical pockets
  • follicular epithelium made of follicular cells surround a single, large oocyte
  • basement membrane of the follicular epithelium defines the outer boundary
  • avascular- oocyte depends on follicular cells for delivery of nutrients and removal of metabolic wastes
  • the menstrual cycle induces dramatic morphological and metabolic changes in the oocyte, follicular epithelium, and surrounding stroma
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9
Q

Oocyte formation

A
  • occurs during fetal development in females
  • primordial germ cells differentiate into oogonia
  • oogonia proliferate through mitosis to number in the millions
  • oogonia enter meiosis and arrest in prophase of the first meiotic division. They are now primary oocytes
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10
Q

Primordial follicle formation

A
  • stromal cells surrounding each primary oocyte reorganize into a follicular epithelium
  • occurs during fetal development only. The number of primordial follicles declines over time due to follicular growth or atresia
  • recent finding: oogonia persist in the adult human ovary- future infertility treatments
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11
Q

Primordial follicle histology

A
  • primary oocytes: very large (25 um diameter), spherical cells with euchromatic nuclei, eosinophilic cytoplasm
  • simple, squamous follicular epithelium: suggests low metabolic activity
  • follicular cell apical surfaces press against the oocyte; basal surfaces face out
  • the most numerous follicle in fertile ovaries
  • dormant state
  • densely packed in outer portions of the cortex
  • primordial follicle= primary oocyte + simple, squamous follicular epithelium
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12
Q

Follicular growth overview

A
  • oocytes grow in size (25 to 120)
  • follicular epithelium grows
  • fluid accumulates in the follicle
  • stromal cells surrounding the follicle reorganize and differentiate
  • stages 1) primordial follicle 2) unilaminar primary follicle 3) multilaminar primary follicle 4) secondary/antral follicle 5) mature/graafian follicle
  • at any point in the process, the follicle can undergo atresia, a form of programmed cell death for the oocyte and follicular epithelium
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13
Q

Follicle activation

A
  • occurs at the state of the 28-day menstrual cycle, beginning at puberty
  • triggered by follicle-stimulating hormone FSH from the pituitary
  • FSH triggers follicular cells to produce aromatase, which converts androstenedione to estrogen
  • estrogen promotes follicular cell mitosis, resulting in follicle growth
  • only a subset of primordia follicles respond to FSH, while others remain dormant
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14
Q

Unilaminar primary follicle

A
  • primary oocyte grows rapidly: nucleus expands and organelles proliferate
  • follicular cells proliferate
  • follicular epithelium becomes simple, cuboidal epithelium, indicating increased metabolic activity
  • unilaminar primary follicle = primary oocyte + simple cubodial follicular epithelium
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15
Q

Multilaminar primary follicle

A
  • primary oocyte grows further
  • follicular cells continue to proliferate and produce estrogen
  • follicular epithelium becomes stratified, cubodial and is now called the granulosa
  • follicular cells are now called granulosa cells
  • zona pellucida: thick eosinophilic layer of glycoproteins secreted by the primary oocyte. The zona pellucida promotes sperm association and activation much later, during fertilization
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16
Q

Transport and signaling within follicles

A
  • blood vessels do not penetrate follicles. All signals and nutrients must cross the follicle basement membrane, the granulosa, and the zona pellucida to the primary oocyte
  • -gap junctions between granulosa cells and between granulosa cells and the oocyte facilitate transport and signaling across the granulosa and zona pellucida
  • multilaminar primary follicle = primary oocyte + stratified, cuboidal epithelium
  • filopodia from granulosa cells penetrate the zona pellucida to contact oocyte microvilli
17
Q

Secondary (antral) follicle

A
  • also called an antral follicle
  • the oocyte has completed its growth
  • granulosa cells continue to proliferate
  • granulosa cells produce follicular liquid, containing hyaluronic acid, steroids, steroid-binding proteins, and other substances
  • follicular liquid containing spaces within the follicle coalesce to a single area called antrum
  • secondary follicle= primary oocye +stratidied, cuboidal epithelium + one or more fluid filled spaces
18
Q

Granulosa rearrangements in secondary follicles

A
  • within further follicular liquid accumulation in the antrum, the oocyte, and granulosa cells are pushed to the periphery
  • along most of the follicles surface, the granulosa has a uniform thickness
  • near the oocyte the granulosa cells form a mound called the cumulus oophorus in which the oocyte is embedded. The granulosa cells that directly surround the oocyte form the corona radiata
19
Q

Mature (Graafian follicle)

A
  • in humans usually only one activated follicle reaches this stage while the others undergo atresia
  • follicular liquid accumulates dramatically enlarging the follicle to a diameter of 2 cm or greater
  • their tremendous size causes stigma which is a whitish, transparent bulge on the ovary surface
20
Q

Identifying follicles

A
  • primordial follicle: central primary oocyte surrounded by simple, squamous follicular epithelium
  • unilaminar primary follicle: central primary oocyte surrounded by simple, cuboidal follicular epithelium
  • multilaminar primary follice: central primary oocyte surrounded by stratified, cuboidal epithelium called the granulosa
  • secondary follicle: central or acentric primary oocyte surrounded by granulosa, with one or more fluid spaces
  • Graafian follicle: an extremely large secondary follicle that bulges the ovary surface outward
21
Q

Theca folliculi

A
  • the stroma around developing follicles rearranges to form a sheath called the theca folliculi
  • there are two layers externa and interna
22
Q

Theca externa

A
  • outer layer
  • provides structural support the follicle
  • smooth muscle cells, fibroblasts, and collagen fibers
  • blends with the stroma
23
Q

Theca interna

A
  • inner layer
  • many cells differentiate to secrete the steroid hormones androstenediones (an androgen) the precursor to estrogen
  • ultrastructurally, these cells have extensive smooth ER, large mitocondria with tubular cristae, and numerous lipid droplets
  • histologically they have large decondensed nuclei and pale, foamy looking cytoplasm
  • the theca interna becomes highly vascular to transport hormones produced by follicle
24
Q

Atretic follicles

A
  • atresia is the programmed cell death of ovarian follicles
  • can occur at any point during follicular development
  • includes apoptosis of granulosa cells, apoptosis and autolysis of the oocyte, and destruction of the zona pellucida (if present)
  • small atretic follicles (from primordial follicles) vanish quickly
  • large atretic follicles (from secondary follicles) display dying granulosa cells with pyknotic nuclei, which slough off into the antrum. Later these follicles collapse and their basement membrane thickens into a transcient, collagenous scar the corpus fibrosum
25
Q

Interstitial glands

A
  • after follicle atresia, the surrounding theca interna usually reverts to regular stroma. When they retain their hormone-producing character, they form interstitial glands
  • histology: groups of hormone-producing cells (pale, eosinophilic with foamy cytoplasm and euchromatic nuclei) in the cortex but not associated a follicle
  • most significantly present in humans during early puberty
26
Q

Ovulation overview

A
  • ovulation is the final release of a secondary oocyte from the ovary by rupture of a graafian follicle into the peritoneal space
  • separates the follicular phase of the ovarian cycle (follicules growth) from the luteal phase (corpus luteum develops)
  • luteinizing hormone (LH) stimulates ovulation by triggering changes that weaken the folliclewall and increase follicular liquid production
27
Q

Oocyte changes near ovulation

A
  • hours prior to ovulation: the primary oocyte completes a highly asymmetric first meiotic division. One nucleus extruded as a tiny cell called the first polar body
  • immediately prior to ovulation: the oocyte commences the second meiotic division. Arrests at metaphase. Now called a secondary oocyte
  • with fertilization: the secondary oocyte completes a highly asymmetric second meiotic division. Produced a a tiny second polar body and a mature ovum
  • without fertilization: the secondary oocyte degenerates after 24 hours
28
Q

Transfer of oocyte to the oviduct

A
  • oocyte complex= secondary oocyte + zona pellucida + corona radiata
  • ovulation expels the oocyte complex into the peritoneal cavity
  • coagulation of follicular liquid holds the oocyte complex on the ovary surface
  • finger-like fimbriae that fringe the oviduct opening sweep the ovary surface
  • beatinf of cilia lining the fimbriae draw the oocyte complex into the oviduct
29
Q

Origin of corpus luteum

A
  • arises from the ruptured follicle after ovulation
  • walls of the ruptured follicle collapse into folds
  • LH: converts the granulosa cells and theca interna cells of the collapsed follicle wall into luteinized granulosa cells and luteinized theca cells
  • granulosa cells differentiate into steroid-producing cells
  • both cells undergo hypertrophy ( cell growth without division)
  • massive thickening of collapses follicle wall: makes corpus luteum extremely large (2-3 cm)
  • Lipochrome pigments: accumulate in luteinized granulosa cells. Gives corpus luteum its yellowish collor
  • bleeding fills the former antrum with clot. Later CT invades
30
Q

Corpus Luteum Histology

A
  • luteinized granulosa cells: large, pale, eosinophilic cells with foamy-appearining cytoplasm and large euchromatic nuclei. Ultrastructure: prominent smooth ER, large mitochondria with tubular cristae, numerous lipid droplets
  • luteinized theca cells: similar, but darker and smaller
  • relative locations: luteinized granulosa cells make up the bulk of the corpus luteum; luteinized theca cells occupy the outer contours of its convoluted edges
  • higher vascular, as expected for an endocrine organ
31
Q

Corpus luteum function

A
  • secretes the steroid hormones estrogen and progesterone
  • among the various functions of these formones, progesterone is critical for stimulating the uterine lining to prepare for embryo implantation
32
Q

Fates of the corpus luteum

A
  • after 10-12 days the corpus luteum requires further hormone stimulation or undergoes luteolysis
  • macrophages engulf remaining debris
  • a large scar of dense connective tissue called the corpus albicans forms, lasting several monthss
  • loss of progesterone production triggers menstruation
  • in the case of pregancy the uterine lining must be maintained to sustain the developing embyro
  • trophoblast cells forming the outermost layer of an implanting embryo secrete HCG which prevents the corpus luteum from undergoing luteolysis thus progesterone levels are sustained

MS 1 Unit 7 Microscopic Anatomy (4 decks)

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