Follicular atresia is the break-down of the ovarian follicles. It occurs continually throughout a woman's life, as she is born with approximately 400,000-600,000 follicles and will only ovulate around 400 in her lifetime.

The granulosa cells stop growing and detach from the basal lamina

Basal lamina

The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below....

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The oocyte

Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...

 dies and the whole unit is phagocytosed.

Theca interna cells may persist and secrete androgens, at which point they are known as interstitial cells, which are active from childbirth until menopause.