Lecture 3: Female tract, oogenesis and endocrine 1 Flashcards Preview

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 What is oogenesis?

The formation and development of an ovum 


Different stages of follicle development?

  • Primordial 
  • Primary (30-50 for 2-3 months)
  • Secondary (15-20 for 2 weeks rapid growth) -loss by atresia 
  • Tertiary Follicle (1-2)


  • Release of a secondary oocyte within corona radiata


Oogonia/oocyte number throughout life?


Formation of oocytes from oogonia?

Following the mitotic division that forms a large number of germ cells (oogonia) , Meiosis begins but is not completed

Meiosis halts just prior to metaphase 1 at the end of prophase and these are now called oocytes 

These oocytes remain arrested until ovulation (12-50 years later) 


The ovarian cycle begins with?

  • Three months before ovulation many primordial follicles become activated (recognisable by the number of granulosa calls that surrond the oocyte) = Follicular wave 
  • It takes about 85 days from activation to antrum formation 
  • They compete with each other to become the dominant follicle in terms of growth with the others dying. 
  • Ovulation occurs from one ovary at a time (unknown mechanism) 


Primordial follicle structure

  • Very thin almost invisible zona pellucida 
  • Flat granulosa cells with stromal cells surrounding 


Primary and Secondary follicle structure? 

  • Granulosa cells proliferate slowly and then rapidly 
  • Theca cells develop outside the basement membrane that are LH receptive and produce androgens
  • Granulosa cells are receptive to FSH and produce: oestrogen, inhibin and AMH 


Steriod Pathway?

Progesterone is converted to 

Androgen that is aromatosed to 


  • These pathways can go both forward and backwards mostly 


Two theories of follicular steriodogeneis?


  • Theca cells in response to LH are making progesterone and androgens 
  • Granulosa cells then convert these to Oestrogens (most potent being oestradiol) 


Tertiary Follicle structure? 


  • Follicular fluid filled Antrum forms
  • Granulosa cells still miltilayerd and cuboidal 
  • Theca interna and externa visible  
  • cumulus oophorous - granulosa cells currounding oocyte 
  • mural granulosa cells lining the wall of the antrum 



Zona Pellucida structure, formation and function?


  • Protein ZP1 is present in primordial follicles 
  • ZP2 and ZP3 are added to the activated follicles 
  • Very important for filtering normal sperm in and blocking polyspermy as well as fertilisation from other species sperm. 


Formation and role of AMH and FSH?



  • AMH - Antimullerian hormone 
  • Produced in the granulosa cells of larger tertiary follicles
  • Supresses follicular recruitment and development 
  • FSH drives proliferation of Granulosa cells so at the secondary and tertiarty follicular levels it becomes gonadotrophin-dependent growth (antral growth opposed to preantral) Before this (eg. primordial) is non-gonadotrophin dependent 


How is the egg released?

  • A dominant follicle is said to be about 15mm 
  • Estrogen feedback flips and causes a surge in LH 
  • 12-24h after LH peak you get ovulation 
  • A part known as the Stigma pushes out from the side of the ovary. 
  • The oocyte then must get into the fillopian tube and theca cells begin to leutinise  
  • The corpus luteum forms and produces progesterone and estrogen before regressing to corpus albicans 


Fillopian tube regions?

  1. Infundibulum (with fimbrae) 
  2. ampulla 
  3. isthmus 
  4. intramural/interstitial portion


Fillopian tube structure?

  1. Epithelial lining 
  2. muscular coat -inner circular, outer longitudinal 
  3. serosal coat 


  • (i) Ciliated 
  • (ii) secretory 
  • Responsive to steroids 


effects of E2 (estrogen) of the FT?

E2 Promotes: 

  • increase in cilia 
  • increase in secretory activity 
  • increase in muscular activity 

Thus the early peak in Egets the FT ready for the oocyte 


Effects of P4 (progesterone) in the FT?

P4 Promotes: 

  • Decreased in muscular activity 
  • decrease in cilia BUT increase in the beat frequency after estrogen priming 
  • Decrease in volume of secretions