Oogenesis- Lecture 5

Question 1

Mitosis

Answer 1

Diploid cell —> Diploid cell Two identical daughter cells are produced.

Question 1

1st meiotic “reductional” division

Answer 1

Separates homologous chromosomes —> each daughter cell has only 1 copy of each homolog (recombination). Prophase 1, Metaphase 1, Anaphase 1, Telophase 1 (polar body), Prophase 2, Metaphase 2, Anaphase 2, Telpphase 2 (polar body).

Question 2

Primary follicle

Answer 2

Activation of primordial follicle. Oocyte surrounded by a single layer of cuboidal granulosa cells. Formation of zona pellucida starts

Question 4

Oogenesis

Answer 4

Formation of female gamete. The differentiation of a highly specialized gamete, the oocyte, starting from an undifferentiated stem cell. The progress of oogenesis starts in early embryonic life.

Question 4

Follicle

Answer 4

Oocyte surrounded by stomatic cells (granulosa). There are different developmental stages.

Question 5

Prophase 1

Answer 5

Leptotene- thin threads. Zygotene- paired threads. Pachytene- thick threads. Diplotene- two threads Diakinesis- moving through.

Question 6

Secondary follicle

Answer 6

The granulosa cells proliferate so the oocyte is now surrounded by several layers of granulosa cells. Stromal cells by the basement membrane align and become theca cells. Follicle has an independent blood supply and sensitive to hormonal regulation.

Question 6

Tertiary/antral follicle

Answer 6

Fluid filled cavities form between the granulosa cells that come together to form the antrum. The theca differentiates into theca externa and interna. Theca externa: fibroblast like required from for ovulations. Theca interna: LH responsive steroidogenic.

Question 7

LH

Answer 7

Luteinizing hormone. Receptors on thecal cells and then also of granulosa cells. Responsible for maturation of oocyte and triggers ovulation.

Question 9

Prenatal oogenesis

Answer 9

Primordial follicle number is set by birth.

Question 9

Steroid production

Answer 9

Theca interna: LH responsive, produce androgen. Granulosa cells: FSH responsive, aromatase androgen to estradiol. Estradiol increases as follicles grow.

Question 10

2nd meiotic division

Answer 10

separates the two sister chromatids from each other.

Question 11

Primordial follicle

Answer 11

Formation occurs during foetal life. A pool of primordial follicles become progressively depleted during a females lifetime. The primordial follicle is surrounded by a single layer of pregranulosa cells.

Question 12

Graffian/preovulatory follicle

Answer 12

The fluid filled cavity has reached maximum size. Oocyte is located inside antrum.

Question 13

Oogonia

Answer 13

Once the PGC reach genital ridge they lose motility and become oogonia. They are interconnected by cytoplasmic bridges and multiple by mitosis.

Question 15

Gonadotropins

Answer 15

Follicles become sensitive to the gonadotropins FSH and LH. Receptors expressed on follicle cells.

Question 16

Folliculogenesis

Answer 16

Formation of a antral follicle starting from a primordial follicle.

Question 17

Primordial germ cells

Answer 17

The stem cells of oogenesis. They migrate from yolk sac to genital bridge and multiply by mitosis

Question 19

Spermatogenesis

Answer 19

Formation of male gamete

Question 20

FSH

Answer 20

Follicle stimulating hormone. FSH receptors on granulosa cells. Stimulates follicular growth.

Question 21

Meiosis

Answer 21

A specialized form of cellular division which only occurs in gametes i.e. oocytes and spermatozoa. The number of chromosomes is reduced so that the resulting cells only have copy of each homolog. Diploid cell —> Haploid cell

Question 22

1st meiotic block of meiosis

Answer 22

The oocyte grows, increasing in volumne 200 times. The zona pellucida forms and cytoplasm matures.