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Anatomy and functionEdit
In the primary ovarian follicle, and later in follicle development (folliculogenesis), granulosa cells advance to form a multilayered cumulus oophorus surrounding the oocyte in the preovulatory or Graafian follicle.
The major functions of granulosa cells include the production of sex steroids, as well as myriad growth factors thought to interact with the oocyte during its development. The sex steroid production consists of follicle-stimulating hormone (FSH) stimulating granulosa cells to convert androgens (coming from the thecal cells) to estradiol by aromatase during the follicular phase of the menstrual cycle. However, after ovulation the granulosa cells turn into granulosa lutein cells that produce progesterone. The progesterone may maintain a potential pregnancy and causes production of a thick cervical mucus that inhibits sperm entry into the uterus.
Embryology of ovarian granulosa cells Edit
In the development of the urinary and reproductive organs, the oogonia become invaginated in the gonadal ridge.
In the 1970’s, evidence emerged that the first cells to make contact with the oogonia were of mesonephric origin. It was suggested that mesonephric cells already closely associated with the oogonia proliferated throughout development to form the granulosa cell layer.
Recently this hypothesis has been challenged with some thorough histology. Sawyer et al. hypothesised that in sheep most of the granulosa cells develop from cells of the mesothelium (i.e., epithelial cells from the presumptive surface epithelium of the ovary). 
The embryological origin of granulosa cells remains controversial.
Cell culture of granulosa cells can be performed in vitro. Plating density (number of cells per volume of culture medium) plays a critical role for the differentiation. A lower plating density makes granulosa cells exhibit estrogen production, while a higher plating density makes them appear as progesterone producing theca lutein cells. 
- ↑ PMID 6422764 (PMID 6422764)
- ↑ Satoh M (1991). Histogenesis and organogenesis of the gonad in human embryos. J Anat 177: 85–107.
- ↑ Upadhyay S, Zamboni L (1982). Preliminary observations on the role of the mesonephros in the development of the adrenal cortex. Anat Rec 202 (1): 105–111.
- ↑ Zamboni, L., Bezard, J., and Mauleon, P. (1979). The role of the mesonephros in the development of the sheep fetal ovary. Annales de Biologie Animal Biochimie et Biophysique 19, 1153-78.
- ↑ Sawyer H, Smith P, Heath D, Juengel J, Wakefield S, McNatty K (2002). Formation of ovarian follicles during fetal development in sheep. Biol Reprod 66 (4): 1134–50.
- ↑ Portela VM, Zamberlam G, Price CA (April 2010). Cell plating density alters the ratio of estrogenic to progestagenic enzyme gene expression in cultured granulosa cells. Fertil. Steril. 93 (6): 2050–5.
- Histology at Boston University 18404loa - "Female Reproductive System: ovary, cumulus oophorus"
- Histology at Boston University 14808loa - "Female Reproductive System: ovary, membrana granulosa"
- MeSH Granulosa+Cells
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