Question

What is cumulus oophorus?

Answer 1

Cumulus oophorus refers to an appearance in the ovary in which multiple granulosa cells enlarge around a developing oocyte at the time of fertilization. These cumulus cells serve multiple functions in the maturation of the oocyte.

Complete answer:
Cumulus oophorus is defined as a group of closely associated granulosa cells, which surrounds the oocyte in the antral ovarian follicle. These clusters of cells appear in the mature follicle. The innermost layer of the cells forms the corona radiata. Usually, a cumulus oophorus is visualized 12-24 hours before ovulation. It comprises a collection of the cells in a mature follicle that protrude into the cavity of the follicle. It is a sign of imminent ovulation, but its absence has little significance in predicting the maturity of the oocyte.
In response to the preovulatory gonadotropin surge the oocyte resumes meiosis and the cumulus cells start producing hyaluronic acid which is deposited into intercellular spaces. This is known as cumulus expansion.

The fully matured cumulus oophorus exerts three major functions:

Before ovulation, cumulus oophorus supports oocyte maturation.
During ovulation, it conducts the oocytes into the oviduct.
After ovulation, it takes part in the complex mechanisms controlling the access of spermatozoa to the oocyte.

Note: Cumulus oophorus, an investing structure unique to oocytes of higher mammals, is induced to synthesize an extensive extracellular matrix by ovulatory stimulus, leading to the characteristic pre-ovulatory expansion of the cumulus-oocyte complex.