Primary Multilaminar
Follicle
Once oocyte growth is completed, the granulosa cells proliferate and arrange into multiple layers. The follicle at this stage is consequently considered a primary multilaminar follicle. This step in development is dependent upon FSH. FSH both induces proliferation of granulosa cells and increases the number of FSH receptors per granulosa cell, thus accentuating its own effects. The thecal cells surrounding the follicle also differentiate into two layers: the theca interna and theca externa. It is currently held that LH drives differentiation of thecal cells.
