Ovarian follicle

Ovarian follicle
Histology section of a mature ovarian follicle. The oocyte is the large, round, pink-staining cell at top center of the image.
Details
Precursor	Cortical cords
Identifiers
Latin	Folliculus ovaricus
MeSH	A05.360.319.114.630.535
TA	A09.1.01.013
FMA	18641
Anatomical terminology []

An ovarian follicle is a roughly spheroid cellular aggregation set found in the ovaries. It secretes hormones that influence stages of the menstrual cycle. Women begin puberty with about 400,000 follicles, each with the potential to release an egg cell (ovum) at ovulation for fertilization. These eggs are developed only once every menstrual cycle.

Ovarian follicles are the basic units of female reproductive biology. Each of them contains a single oocyte (immature ovum or egg cell). These structures are periodically initiated to grow and develop, culminating in ovulation of usually a single competent oocyte in humans. They also consist of granulosa cells and theca of follicle.

Once a month, one of the ovaries releases a mature egg (ovum), known as an oocyte. A follicle is an anatomical structure in which the primary oocyte develops. The nucleus of such an oocyte is called a germinal vesicle (see picture).

Cumulus oophorus is a cluster of cells (called cumulus cells) that surround the oocyte both in the ovarian follicle and after ovulation.

It contains numerous granulosa cells.

Granulosa cells or follicular cells are cells that surround the oocyte within the follicle; their numbers increase directly in response to heightened levels of circulating gonadotropins or decrease in response to testosterone. They also produce peptides involved in ovarian hormone synthesis regulation. Follicle-stimulating hormone (FSH) induces granulosa cells to express luteinizing hormone (LH) receptors on their surfaces; when circulating LH binds to these receptors, proliferation stops.