Question

Explain the development of ovum from an oogonium in human female

Answer 1

Stage 1: primordial germ cell undergoes mitosis to produce two Oogonia (immature reproductive cells) → cells are diploid

Stage 2: Each Oogonia also undergoes cell division to produce two diploid primary oocytes. It is surrounded by a layer of follicle cell

Stage 3: Each primary oocyte starts to undergo meiosis to become a secondary oocyte and first polar body (haploid)

Stage 4: The follicle cells surrounding the primary follicle develop into secondary follicle. Follicle layer of the secondary follicle thickens and form the Graafian follicle. When the graafian follicle becomes mature, it moves towards the surface of the ovary and rupture to release the secondary oocytes 

Stage 5: The secondary oocytes that has complete meiosis II  producing the mature gamete (Ova) - haploid

- This stage only occur when fertilisation of the oocytes by the sperm has occurred

Answer 2

Answer:

Oogenesis is the process by which an ovum or a secondary oocyte is produced from the oogonia.

Oogonium is the singular form, oogonia are plural.

First, during the embryonic period of a female, the primordial germ cells differentiate to form numerous oogonium or oogonial cells.

The cell pool is maintained by repeated mitotic divisions.

Now the oogonia grows into the primary oocytes as the onset of meiosis I occur. After completion of meiosis I, diploid primary oocytes produce two types of haploid cells- a secondary oocyte and the first polar body.

The secondary oocyte completes its meiotic division after sperm entry and produces another polar body and a mature ovum. The first polar body also divides to form two new polar bodies.

Note: Oogenesis is a discontinuous process. It is arrested twice.

First, the primary oocyte is arrested in prophase I; it releases after puberty.

Second, the secondary oocyte is arrested at metaphase II; it releases upon sperm entry.