Ovarian function and failure: The role of the oocyte and its molecules

Abstract

The ovaries are complex organs by virtue of their primary function and are also genetically unique, since they have a mixture of both somatic cells and germ cells. At birth, each ovarian germ cell or oocyte is enclosed by a specialized population of somatic (pregranulosa) cells to form the follicle, the most basic functional unit of the female gonads. Most follicles present in the ovaries of neonates exist in a state of growth arrest and are referred to as primordial follicles. Although the number of these follicles endowed in the ovaries at birth varies among species (from 2×104 to 4×104 in mice to 1×106-2×106 in humans), this stockpile of oocytes is non-renewable in all species and must provide for the entire reproductive needs of the female throughout adult life. By the age of 50 years, the ovaries in most women are exhausted and menopause ensues as a direct consequence of ovarian senescence. © 2009 Springer-Verlag US.