What is oogenesis? Give a brief account of oogenesis.

Explanation

The process of formation of mature female gamet is called .Oogensis. It is initiated during the embroyonic development stage when a couple of million gamet mother cells (oogonia) are formed within each foetal ovary and do not multiply thereafther. These cells start divison and stop and process at prophase I of the meiosis - I. At this stage they are called primary oocytes.
Each primary Oocyte is sorrounded by a flattened layer of follicular cells, it is called primary follicle. These follicular cells become Puberty------ cuboidal and proliferate to produce a stratified epithelium called membrana.granulosa. These Adult cells are called granulosa cells. Follicles at this reproductive life Second stage are called primary follicles. A polar body homogenous membrane, the .zona
pellucida, appears between primary oocyte and granulosa cells.

A cavity appears within the membrana granulosa increases in size and the wall of follicle becomes thin. The oocyte lies eccentrically in the follicle sorrounded by granulosa cells. As the follicle expands the stromal cells sorrounding membrana granulosa become condensed to form a inner covering .theca internal and outer covering .theca externa.. Now these are called .secondary follicles.. The cells of theca interna later secrete a hormone called .oestrogen.. The primary oocyte within the graafian undergoes two meoitic divisons, finally changing into a Graafian follicle.. The Graafian follicle is at first very small, later it enlarges, becomes so big that it not only reaches the surface of ovary, but also forms a bulging in this situation. Ultimately the follicle ruptures releasing the ovum.