Lect. 2 - Gametogenesis II

Question 1

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

Answer 1

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

Question 2

follicular structure during Fetal period

Answer 2

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

Question 3

follicular strucutre at later fetal period through birth

Answer 3

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

Question 4

follicular structure at Birth to puberty

Answer 4

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

Question 5

After puberty

Answer 5

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

Question 6

Ovulation

Answer 6

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

Question 7

after fertilization

Answer 7

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

Question 8

What does the theca externa produce?

Answer 8

angiogenesis factor

Question 9

Theca interna

Answer 9

Has LH receptors and secretes testosterone.

Question 10

Mural granulosa cells

Answer 10

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

Question 11

Cumulus (oophorus) cells

Answer 11

will facilitate release of ovum at ovulation

Question 12

Zona Pellucida

Answer 12

involved in fertilization

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

how many oocytes will survive to puberty?

Answer 15

40,000

Question 16

when do some oocytes resume meiosis?

Answer 16

at the beginning of each munstrual cycle