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
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
*completion of second meiotic division
*fertilized ovum + second polar body
What does the theca externa produce?
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
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?