Final answer:
The size of the follicle is influenced by the number of granulosa and theca cells present which contribute to its development and estrogen production. A process involving hormonal stimulation and negative feedback determines that typically only one, known as the dominant follicle, will mature enough to release an oocyte.
Step-by-step explanation:
The size of the follicle during ovulation is determined by several factors, including the number of granulosa and theca cells it has. These cells are key in producing estrogen in response to LH (luteinizing hormone) stimulation. Increased estrogen leads to a systemic increase in plasma estrogen concentrations. However, a high concentration of estrogen triggers a negative feedback mechanism that reduces the production of GnRH (gonadotropin-releasing hormone), LH, and FSH (follicle-stimulating hormone). Since tertiary follicles require FSH to grow, most undergo atresia, or cell death. Amidst these conditions, only one follicle, called the dominant follicle, will typically survive and continue to develop until it is ready to release an oocyte.
Prominent factors that contribute to a follicle’s dominance and survival include its size, the number of granulosa cells, and the abundance of FSH receptors on these cells. FSH stimulates the growth of tertiary follicles and LH enhances estrogen production by granulosa and theca cells. The eventual rupture of the mature follicle leads to the release of the oocyte, followed by the transformation of the remaining cells into the corpus luteum.