The ovary is the site of the development of the oocyte.
Within the ovaries, follicles develop.
Each follicle houses an oocyte, which matures simultaneously with the follicle.
The primary follicle houses an oocyte encapsulated by a coating called the zona pellucida.
It also contains a layer of granulosa cells that surrounds the oocyte.
The secondary follicle contains many more granulosa cells, and an accumulation of follicular fluid that is secreted by granulosa cells.
This fluid coalesces in the follicle to form the antrum.
A mature follicle is much larger than a secondary follicle and the antrum occupies a greater portion of the follicle.
It is within the mature follicle that the first meiotic division of the oocyte is completed to produce a secondary oocyte and the first polar body.
The secondary oocyte receives most of the cytoplasm from the cell division.
However, the nuclei and chromosomes are divided equally.
The polar body degenerates.
The mature follicle ruptures at ovulation to release the secondary oocyte and a corona of granulosa cells into the uterine tube.
The second meiotic division cannot be completed unless the secondary oocyte unites with a sperm cell.
As a result of this division, a second polar body is formed, and the oocyte and sperm nuclei combine to form a zygote.