The cumulus oophorus (Latin cumulus=heap, Greek oo=egg + phor=carrier; Latinized ending "-us"), also called discus proligerus, is a cluster of cells (called cumulus cells) that surround the oocyte both in the ovarian follicle and after ovulation. In the antral follicle, it may be regarded as an extension of the membrana granulosa. The innermost layer of these cells is the corona radiata.
Functions of the cumulus oophorus include coordination of follicular development and oocyte maturation. Mechanisms of the latter include stimulation of amino acid transport and sterol biosynthesis and regulation of oocyte gene transcription.
It also provides energy substrates for oocyte meiotic resumption and promotes glycolysis.
In addition, it provides protection for the oocyte. Also used in cloning procedures 
Gene expression profiling
As a part of the process of in vitro fertilization, gene expression profiling of cumulus cells can be performed to estimate oocyte quality and the efficiency of an ovarian hyperstimulation protocol, and may indirectly predict oocyte aneuploidy, embryo development and pregnancy outcomes. Increased knowledge in these aspects is useful in, for example, embryo selection.
In contrast, genes where increased expression is correlated with lower oocyte competence or worse pregnancy outcomes include: BDNF, CCND2, CXCR4, GPX3, HSPB1, DVL3, DHCR7, CTNND1, TRIM28, STAR, AREG, CX43, PTGS2, SCD1 and SCD5.
- Gilbert, Scott F. Developmental Biology (Ninth ed.). Sinauer Associates, Inc. p. 126. ISBN 0878933840.
- The Evian Annual Reproduction (EVAR) Workshop Group 2010; Fauser, B. C. J. M.; Diedrich, K.; Bouchard, P.; Domínguez, F.; Matzuk, M.; Franks, S.; Hamamah, S.; Simón, C.; Devroey, P.; Ezcurra, D.; Howles, C. M. (2011). "Contemporary genetic technologies and female reproduction". Human Reproduction Update. 17 (6): 829–847. doi:10.1093/humupd/dmr033. PMC . PMID 21896560.
- Anatomy photo: Reproductive/mammal/ovary5/ovary3 - Comparative Organology at University of California, Davis - "Mammal, bovine ovary (LM, Medium)"
- Swiss embryology (from UL, UB, and UF) dbefruchtung/objectbefru01
- UIUC Histology Subject 366
- Histology image: 18404loa – Histology Learning System at Boston University - "Female Reproductive System: ovary, cumulus oophorus"