Lect. 2 - Gametogenesis II Flashcards Preview

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Flashcards in Lect. 2 - Gametogenesis II Deck (16):

About how many oocytes are present early in embryonic development? and then at birth and puberty?

7 million germ cells at embryonic midterm; 2 million at birth; 40,000 survive to puberty. 400 become ovulated


follicular structure during Fetal period

diploid oogonium not surrounded by follicle cells; no follicle; 1 chromatid/chromosome


follicular strucutre at later fetal period through birth

Diploid primary oocyte; primordial follicle w/ a few flattened follicle cells; 2 chromatids/chromosome


follicular structure at Birth to puberty

Diploid primary oocyte; primary follicle w/ single layer of cuboidal follicle cells; oocyte and follicle cells are connected vie microvilli and gap junctions; zona pellucida separates primary oocyte from folliclular cells; 2 chromatids/chromosomes


After puberty

Diploid primary oocyte; secondary follicle w/ multiple layers of follicle cells and beginning of antrum formation; membrane granulosa surrounds outside of follicle cells; 2 chromatids/chromosome; haploid secondary oocyte + haploid polar body; tertiary follicle w/ multiple layers of follicle cells, corona radiata and large antrum



haploid secondary ooctyte w/ corona radiata and thecal cells + haploid polar body; 2 chromatids/chromosome;meiosis resumes and is arrested at metaphase II


after fertilization

*completion of second meiotic division
*fertilized ovum + second polar body
*1 chromatid/chromosome


What does the theca externa produce?

angiogenesis factor


Theca interna

Has LH receptors and secretes testosterone.


Mural granulosa cells

Develop FSH receptors, synthesize aromatase in response to FSH, aromatase converts testosterone into 17B-estradiol, estrogens stimulate formation of LH receptors on granulosa cells.


Cumulus (oophorus) cells

will facilitate release of ovum at ovulation


Zona Pellucida

involved in fertilization


What are the components of the tertiary (Graafian) follicle in order of external to internal?

Theca externa, theca interna, membrana granulosa, antrum, cumulus cells, ZP, Oocyte


What factors lead to meiotic arrest at the diplotene stage of meiosis?

1. High concentration of cAMP from oocyte and folliclular cells - inactivated MPF
2. cGMP from follicular cells that inactivate phosphodiesterase 3A in oocyte - prevents conversion of cAMP to 5'AMP and maintains high concentration of cAMP


how many oocytes will survive to puberty?



when do some oocytes resume meiosis?

at the beginning of each munstrual cycle