Week 1 Objectives 5: describe formation of ovarian follicles and related major endocrine interactions

Question 1

Female Primordial Germ Cells (4 things to remember)

Answer 1

1. Develop at a site distant from the gonads (like in men)
2. Migrate to developing ovaries and become oogonia
3. All oogonia develop into primary oocytes in the early embryo

Question 2

Primary Oocytes

Answer 2

in most mammalian species, primary oocytes begin the process of meiosis and reach the diplotene stage of meiosis before or shortly after birth

Question 3

@ embryonic midterm =

Answer 3

7 million germ cells are present

Question 4

@ birth =

Answer 4

about 2 million remain

Question 5

@ puberty =

Answer 5

around 40,000 have survived

suspended in the diplotene stage of meiosis

Question 6

at the beginning of the menstrual cycle…

Answer 6

these primary oocytes will resume meiosis (diplotene –> diakinesis)

about 400 will actually be ovulated, most become atretic

Question 7

Structure of the follicle during Oogenesis: Fetal period

Answer 7

Diploid oogonium is not surrounded by a follicle
NO FOLLICLE
1 chromatid/chromosome

Question 8

Structure of the follicle during Oogenesis:: Later fetal period through birth

Answer 8

1. Primordial follicle appears with just a few flattened follicle cells
2. Diploid primary oocyte
3. 2 chromatids/ chromosome

Question 9

Structure of the follicle during Oogenesis: birth to puberty

Answer 9

1. Primary follicle with a single layer of cuboidal follicle cells
2. Diploid primary oocyte
3. Oocyte and follicle are connected via microvilli and gap junctions
4. zona pellucida separates primary oocyte from follicular cells
5. 2 chromatids/ chromosome

Question 10

Structure of the follicle during Oogenesis: After puberty

Answer 10

Secondary follicle with multiple layers of follicle cells

1. beginning of antrum formation
2. diploid primary oocyte
3. membrane granulosa surrounds outside of follicle cells
4. 2 chromatids/chromsome
5. beginning of antrum

Question 11

Structure of the follicle during Oogenesis: After puberty (continued)

Answer 11

Primary oocyte –> Haploid secondary oocyte + haploid polar body

Tertiatry follicle with multiple layers of follicle cells, corona radiata and large antrum

2 chromatids/chromosome

Question 12

Tertiary follicle: structure

Answer 12

multiple layers of follicle cells, corona radiata, and large antrum

1. Mural granulosa = cells between membrane granulosa and antrum
2. cumulus cells = cells between zona pellucida and antrum

Question 13

Ovulation

Answer 13

Haploid secondary oocyte with corona radiata and thecal cells + haploid polar body

Granulosa cells develop FSH receptors and LH receptors

Circulating FSH stimulates granulosa cells to produce estrogen

2 chromatids/chromosomes

Meiosis resumes, arrested at Meiosis II

Question 14

Meiosis II suspension is due to

Answer 14

LH surge which shuts down gap junctions between granulosa cells and oocyte

cAMP concentration is reduced, allowing activation of MPF

Question 15

Tertiary follicle components

Answer 15

Graafian follicle

Theca externa, interna, membrane granulosa, mural granulosa cells, antrum, cumulus (oophorus cells: will facilitate release of ovum at ovulation), zona pellucida, oocyte

Question 16

theca externa produces

Answer 16

angiogenesis factor

Question 17

theca interna

Answer 17

possesses LH receptors and secretes testosterone

Question 18

Membrana granulosa

Answer 18

nothing, just a layer

Question 19

Mural granulosa cells

Answer 19

Develop FSH receptors

Synthesize aromatase in response to FSH

aromatase converts testosterone into 17-beta-estradiol

estrogens stimulate formation of LH receptors on

granulosa cells

Question 20

Cumulus (oophorus cells)

Answer 20

facilitates release of ovum at ovulation

Question 21

zona pellucida

Answer 21

involved in fertilization

Question 22

Characteristics of the Graafian follicle

Answer 22

large, projects from the ovary like a blister

takes about 9 days to develop from primordial follicle in humans