An immature OVUM. When the cell undergoes MEIOSIS in the ovary it becomes an ovum and is ready for fertilisation by the spermatozoa. Only a small number of the many oöcytes produced survive until PUBERTY, and not all of them will become ova and be ejected into the FALLOPIAN TUBES.
n. a cell in the ovary that undergoes *meiosis to form an ovum. Primary oocytes develop from *oogonia in the fetal ovary as they enter the early stages of meiosis. Only a fraction of the primary oocytes survive until puberty, and even fewer will be ovulated. At ovulation the first meiotic division is completed and a secondary oocyte and a polar body are formed. Fertilization stimulates the completion of the second meiotic division, which produces a second polar body and an ovum.
(egg donation) the transfer of secondary *oocytes from one woman to another. Possible recipients include women with primary or secondary ovarian failure or severe genetic disorders, and women in whom ovulation has been suppressed as an incidental result of drug treatment for another condition (e.g. cancer). Pregnancy rates are higher than with *in vitro fertilization.... oocyte donation
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