Final answer:
The structure where a primary oocyte grows and develops is a follicle, which matures through the process of folliculogenesis, and upon fertilization becomes a fertilized egg.
Step-by-step explanation:
The structure within the ovary in which a primary oocyte grows and develops is called a follicle. During the process of oogenesis, the primary oocyte begins meiosis but is arrested in the prophase stage until adolescence. With the influence of anterior pituitary hormones, follicles in the ovary develop and the primary oocyte completes the first meiotic division, becoming a secondary oocyte and a smaller polar body. At ovulation, if the secondary oocyte is fertilized, it completes the second meiotic division to form a fertilized egg with a full set of chromosomes.
Folliculogenesis is the process of ovarian follicles and oocytes growing and developing, which includes the stages from primordial to primary, secondary, and tertiary follicles, before ovulation occurs. The growing follicle protecting the primary oocyte also secretes a thin acellular membrane called the zona pellucida. Supporting cells within the follicle, such as granulosa and theca cells, aid in its growth and maturation.