(Gr. ôon: egg; kytos: what covers) n. A female germ cell (primary oocyte) that gives rise by meiosis to a polar body and a haploid cell (secondary oocyte), which in turns gives rise to a second polar body and an ootid.
Female reproductive cell. At birth, an ovary contains 1-2 million oocytes; at puberty, only 500'000-400'000 remain. Only 400500 will be ovulated - one every month - until menopause. All others will degenerate at various development stages.
An egg cell that contains 23 chromosomes (one X chromosome and 22 autosomes), which are considered immature. At birth, a woman's ovaries contain all the oocytes she will ever have. Each month about 50 oocytes start to grow and mature, but only one or two normally reach the fully, mature stage. A follicle (bubble of fluid on the surface of the ovary) releases the mature oocyte, which is gathered in by the fringy end of the fallopian tube. During the next two days of the woman's midcycle, the oocyte will travel through the tube. This is the time when the egg can be fertilized if it meets a sperm cell.
Ovum/ Ova The female haploid gamete prior to fertilization by a spermatozoon. Two haploid gametes (oocyte and sperm) combine to produce the single-cell diploid embryo. The female gamete is generally equivalent to what would be termed a secondary oocyte in higher animals, being formed after the meiotic division of a diploid germ cell. As the oocyte matures, it remains in syncytial contact with the rachis to gain nutrients and organelles from nearby gametes, many of which will undergo germline programmed cell death after sharing these components with the surviving oocyte The term is also frequently used to refer to a â€œfertilized oocyteâ€, which is then the diploid cell resulting from the fertilization event and is actually an early embryo.