Female Repro Histo and Physio Flashcards
Pituitary- Ovary Cross-talk
- Corpus luteum dies, E and P levels fall.
- Pituitary responds to falling E and P by increasing FSH secretion
- FSH recruit a cohort of large antral follicles to enter rapid growth phase. Follicles secrete low amounts of E and inhibin.
- E and inhibin negatively feed back on FSH.
- Declining FSH levels progressively cause atresia of all but 1 follicle– leading to selection of dominant follicle, which produces high levels of E.
- High E has positive feedback on gonadotropes– LG (and some FSH) surges.
- LH surge induces metabolic maturation, ovulation, and luteinization. The corpus luteum produces high P, along with E and inhibin.
- High P, E, and inhibin negatively feed back on LH and FSH, returning them to basal levels.
pulsatile GnRH release
Days 15-0 : 1 pulse per hour–> high LH, low FSH
Days 0-15: 1 pluse / 3 hours–> meeting in the middle
back to 1 pulse/ hour
Ovary structure: medulla
Central portion
Loose connective tissue
Blood vessels, lymphatics and nerves
Ovary structure: cortex
Peripheral portion
Contains ovarian follicles
Smooth muscle fibers
Highly cellular connective tissue
Ovarian follicle maturation
ovarian phases
follicular phase
- lasts about 14 days
- only 1 ovary involved in a single menstural cycle
- during follicular phase: FSH stimulates cohort of follicles to mature, follicles produce estradiol, level peaks just prior to ovulation
mid-cycle surge of luteinizing hormone (LH) thru estradiol-mediated mechanism necessary to stimulate ovulation
Histology of ovarian follicles
Distributed throughout cortex
Size indicates the developmental state of the oocyte
Contain:
Ooctyes, Follicular cells (Change in shape and number during follicle development)
Histology of primordial follicle
Earliest stage
Arrested at prophase of the first meiotic division during fetal development
Just beneath the tunica albuginea
Appearance:
Primary oocyte
–Eccentric nucleus with dispersed chromatin and prominent nucleoli
–Single layer of squamous follicular cells
–Surrounded by a basal lamina
Histology of primary follicle
Development of follicular cells
Appearance:
Unilaminar primary follicle
- Primary oocyte (Enlarges, Begins to secrete glycoproteins that will assemble into an extracellular coat (zona pellucida, necessary for fertilization))
-A single layer of cuboidal follicular cells (Hypertrophy)
Multilaminar primary follicle
Primary oocyte
Stratum granulosum
- Several layers of cuboidal to columnar follicular cells
(Hyperplasia, Now called granulosa cells, Avascular)
Zona pellucida
(Glassy membrane, Mature glycoprotein coat)
Theca folliculi
(External to the basal lamina, Stromal (CT) cells)
Secondary follicle (antral follicle)
Accumulation of follicular fluid
Appearance:
- Primary oocyte
(Growth now inhibited by granulosa cells)
- Liquor folliculi in the intracellular spaces of follicular cells (Eventually form a single fluid filled antrum)
- Zona pellucida (Well developed)
- Theca interna (Steroid responsive and steroid producing stromal cells, Highly vascular)
- Theca externa (Smooth muscle cells)
Graafian folicle
Mature follicle
Large, covers full thickness of cortex and creates bulge on surface of ovary
Follicular fluid forms a large central antrum
Appearance:
- Primary oocyte (Eccentric)
- Antrum (Primary feature)
- Cumulus oophorus (Thickened mound of granulosa cells, Will detach prior to ovulation)
- Corona radiata (Granulosa cells that immediately surround oocyte and remain after ovulation, Will become a single layer prior to ovulation)
Ovulation
Mid-cycle surge of LH leads to ovulation. Proteases from fibroblasts degrade collagen fibers of the tunica albuginea and theca externa.
The mural granulosa cell layer fols soon after ovulation.
The basement membrane breaks down, blood vessesl from the theca interna invade the folding granulosa cell layer, and the antral cavity is filled with blood. (corpous hemorrhagicum).
oocyte activities
at ovulation primary oocyte completes 1st meiotic division
produces 2° oocyte & polar body (with an unequal division of cytoplasm)
2° oocyte receives:
nearly all cytoplasm
half of chromosomes
2° oocyte is haploid with 23 css (but still 2N DNA)
after ovulation oocyte "picked up" by fimbriae enters infundibuium transported to uterus by: peristalsis (primary motive force) ciliary action
oocyte enters 2nd meiotic division,
BUT suspended in metaphase II
stays in metaphase II until fertilization
if fertilized, secondary oocyte divides, produces:
another polar body
ovum (haploid, 1N DNA)
Ovulation & follicular atresia
ovulation vs. atresia
ovulation usually produces single fertilizable oocyte BUT, cohort of follicles forms under FSH influence
dominant follicle emerges 1 week before ovulation mechanism selecting dominant follicle unclear remaining follicles become atretic
in follicular atresia: oocyte dies, and antrum collapses granulosa cells stop dividing, detach from basal lamina during atresia some theca interna cells persist make up “interstitial glands”, which secrete androgens thru-out life
Corpus Luteum (histology)
At ovulation, the follicle collapses and transforms into the luteal gland (luteinization)
Breakdown of basement membrane
Invasion of blood vessels (Corpus hemorrhagicum: Fibrin clot in former antral space)
Transformation of cells
- Follicular (granulosa) lutein cells (Large, vacuolated, Centrally located, Form a thick folded layer around the former follicular cavity)
- Theca lutein cells (Smaller, vacuolated, Peripherally located, Cytoplasm more purple)
If fertilization and implantation occur, it increases in size
Corpus luteum (physiology)
after ovulation LH still secreted by pituitary
luteal phase of ovarian cycle (14 days)
follicle undergoes transformation
becomes corpus luteum under effects of LH
persistence of corpus luteum depends on LH
granulosa cells hypertrophy
(now called granulosa lutein cells)
characteristic steroid secreting cells
thecal cells surround granulosa lutein cells
now called theca lutein cells
secrete estrogen and progesterone
receptor synthesis promoted by estradiol
estradiol feeds back on pituitary to inhibit LH secretion
by day 25 LH levels too low to support steroidogenesis
menstruation follows
Corpus albicans
Scar formed from regression of the corpus lutein (luteolysis) after pregnancy or menstruation
Involution
- Cells decrease in size and undergo autolysis
White scar
- Deposition of intracellular hyaline material
- Disappears after several months
Atretic follicles
At any one time, several follicles initiate maturation but only one or two complete it
The remainder degenerate or undergo atresia
Appearance:
- Thick, folded or collapsed follicle
- Intact zona pellucida
- One or more layers of follicular cells
- Remnants of degenerated oocyte
- Macrophages
Oviduct function
oviducts (uterine tube or Fallopian tube)
function:
fertilization usually occurs here
most commonly in ampulla
conveys oocyte to uterus
implantation, development & growth occur in uterus
Fallopian tube (Uterine tube or oviduct) histology
Resembles visceral organs in structure (but without submucosa) Serosa (peritoneum) - Outermost, CT - Contains vasculature Muscular layer (muscularis) - Inner, thick circular layer - Outer, thin longitudinal layer - Peristalsis Lamina propria Mucosa - Simple columnar epithelium Fimbria In the infundibulum Mucosal folds In ampulla and isthmus Ciliated More numerous in infundibulum and ampulla (closer to ovary) Non-ciliated cells Secretory
Hormone effects- oviduct
estrogen increases: endosalpinx epithelial size, blood flow to lamina propria, oviduct specific glycoproteins, ciliogenesis, mucus, muscular tone of the isthmus
progesterion decreases epithelial size and mucus, increases deciliation, relaxes muscular tone
Uterine Cycle
aka endometrial cycle, menstrual cycle described as 28 days in length (but is variable) divided into: 1. menstrual phase 2. resurfacing phase 3. proliferative phase 4. secretory phase 5. ischemic phase
Hormone effects uterus
Proliferative (ovarian follicular phase)
- Reepithelialization of the basal layer
- Estrogen drives cellular proliferation
- Induces expression of progesterone receptors
Secretory (ovarian luteal phase)
- Inhibition of endometrial growth
- Stimulation of uterine glands
- Changes to adhesivity of surface epithelium
- Opposes proliferative effect of estrogen
Menstrual (occurs upon demise of the corpus luteum)
- Coincides with early follicular phase
- Upregulates MMPs
- Upregulation of COX-2 (results in PGF2)
Endometrium overview
Undergoes cyclical changes each month throughout reproductive life
1 mm to 6 mm thick
Two zones:
1.) Stratum functionale
- Thickest portion
- Sloughed during mentstration
- Divided into: Stratum spongiosum
(Broad intermediate layer, spongy appearance) and Stratum compactum
(Thin superficial layer, stromal appearance)
- ) Stratum basale
- Retained during menstration
- Source for the regeneration of the stratum functionale
