Cumulus covers

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Cumulus oophorus or cumulus is a sphere of loosely arranged granulosa (follicular) cells surrounding the ovum or egg. These cells originate from the membrana granulosa layer. The meaning of “Cumulus oophorus” is an egg-bearing little cloud. Cumulus oophorus is also known as discus proligerus. These cells surround the ovum both in the ovarian follicle as well as after ovulation.

Several studies show that the proteins secret by cumulus cells are vital for follicular development, the development and maturation of oocytes, and normal ovulation. They induce the transportation of nutrients to the oocyte, amino acid transport, sterol biosynthesis, and gene transcription in the oocyte. In mammals, cumulus cells also interact with the egg or spermatozoa and promote fertilization. However, the underlying mechanism is not clear. Past research shows that the removal of the cumulus cells from eggs causes a decline in fertilization rates.

Hyaluronic acid is the main cementing material present between the cells in the cumulus oophorus. When a sperm enters the cumulus oophorus, the enzyme hyaluronidase present in the sperm head dissolves the cementing material hyaluronic acid. Upon dissolution of hyaluronic acid, the sperm penetrate the cumulus cells and reach the zona pellucida.

Oocyte maturation inhibitor, a low molecular weight peptide secretes by cumulus cells that control the meiosis in the oocyte.