part of part of ovarian follicle cumulus oophorus A cluster of cells that project into the cavity of the mature ovarian follicle. It is released with the embedded oocyte during ovulation. In order for fertilization to occur this layer must be penetrated by the spermatocyte. [WP,modified]. Wikipedia:Cumulus_oophorus ovarian cumulus discus proligerus MA:0002414 FMA:18659 UBERON:0001306 SCTID:258586009 EMAPA:35267 reproductive structure granulosa cell layer cell cluster