Lecture 2: Gametogenesis II

Question 1

In what stage of meiosis are primary oocytes arrested between birth and puberty?

Answer 1

Diplotene stage of Prophase I

Question 2

After puberty, meiosis resumes in some oocytes. During which stage of meiosis is the oocyte again arrested?

Answer 2

Metaphase II

Question 3

Describe follicular structure in the fetal period with respect to oogenesis.

Answer 3

Diploid oogonium, no follicle, 1 chromatid/chromosome

Question 4

Describe follicular structure in the later fetal period through birth with respect to oogenesis.

Answer 4

Diploid primary oocyte, primodrial follicle with a few flattened follicle cells; 2 chromatids/chormosome

Question 5

Describe follicular structure during birth through puberty with respect to oogenesis.

Answer 5

Diplid primary oocyte, primary follicle with single layer of couboidal follicle cells; ZP separates primary oocyte from follicular cells; 2 chormatids/chromosome

Question 6

Describe follicular structrue after puberty with respect to oogenesis.

Answer 6

Diploid primary oocyte, secondary follicle with mutliple layers of follicle cells and antrum formation beginning; 2 chromatids/chromosome.

Contains haploid secondary oocyte and polar body; later follicle becomes tertiary with follicle cells, corona radiata, antrum

Question 7

Describe follicular structure during ovulation with respect to oogenesis

Answer 7

Haploid secondary oocyte with corona radiata, thecal cells and haploid polar body; 2 chromatids/chromosome

Question 8

Describe follicular structure during ovulation with respect to oogenesis

Answer 8

Completion of second meiotic division; fertilized ovum + second polar body; 1 chromatid/chromosome

Question 9

List the components of the mature Graafian follicle from external to internal.

Answer 9

Theca externa, theca interna, membrana granulosa, mural granulosa cells, antrum, cumulus oophorus, zona pellucida, oocyte

Question 10

Explain how LH receptors are formed on granulosa cells

Answer 10

FSH receptors synthesize aromatase in response to FSH, aromatase converts testosterone into estradiol, estradiol stimulates formation of LH receptors

Question 11

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

Answer 11

High [cAMP] which inactivates MPF (maturation promoting factor); cGMP from follicular cells inactivate phosphodiesterase 3A (maintains high [cAMP])

Question 12

What is the role of LH in ovulation?

Answer 12

Sudden spike in LH activates adenyl cyclase, stimulating progesterone secretion and releasing oocyte/corona radiata

Question 13

What is the fate of the follicle after ovulation occurs?

Answer 13

2nd meiotic division completed, contains fertilized ovum and polar body