ABSTRACT
As in the male, primordial germ cells arising on the yolk sac migrate into the developing ovaries on about the 38th day of development. Once in the ovaries, the germ cells are called oogonia. The ovaries contain the greatest number of germ cells before birth, when they number in the millions. At birth, the number is in the hundreds of thousands; at puberty (menarche), in the tens of thousands; and at menopause, the number is essentially zero. The number of germ cells in a woman's ovaries is in constant decline. A relatively small number of germ cells is lost through ovulation, as are a much larger number through normal cell death (Fig. 6-5). In addition, the ovaries do not have stem cell populations to renew the supply of germ cells.
