Where do the granulosa and thecal cells originate from and what are their functions?

Explanation

Granulosa cells and thecal cells surround the primary follicles to form secondary follicles in the ovaries. The innermost layer of granulosa cells that surround the oocyte is known as the corona radiata. A glycoprotein protective layer, known as the zona pellucida appears. between the oocyte and corona radiata. Cells from the stroma surround the granulosa cells and differentiate as the thecal cells.
During ovulation, granulosa and thecal cells proliferate and become glandular.
They collectively form luteal cells which is the source of oestrogon and progesterone.