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How are ovarian follicles involved in egg development?

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Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

Ovarian follicles are essential structures within the ovary that house and support the development of immature eggs, known as oocytes. Their role in egg development involves several key processes:12

Maturation and Growth: Follicles are present in the ovaries from birth. During the reproductive years, specific follicles are selected to undergo maturation, during which they enlarge and migrate toward the surface of the ovary. In mammals, this includes the formation of a fluid-filled cavity called an antrum, leading to the development of large, mature structures known as Graafian follicles.12
Nutritional and Hormonal Support: The cells lining the follicle, called granulosa cells, and the surrounding sheath, known as the theca, provide critical support. They facilitate the transport of substances necessary for egg growth and are responsible for producing vital hormones, including estrogens, which are essential for the reproductive cycle.12
Ovulation: Once a follicle reaches maturity, it ruptures to release the egg, allowing it to enter the fallopian tube for potential fertilization.1
Post-Ovulatory Function: After releasing the egg, the follicle transforms into the corpus luteum, which secretes progesterone to support pregnancy.12