Bio notes April 8, 2008
, is based on meiosis, but details differ in females and males.
development of mature ova (egg cells), is described in
, on the next page.
production of mature sperm cells, is a continuous and prolific process in the adult male. Each ejaculation of a human
male contains 100 to 650 million sperm cells, and males can ejaculate daily with little loss of fertilizing capacity.
Spermatogenesis occurs in the seminiferous tubules of the testes.
describes the process in some
Oogenesis differs from spermatogenesis in three major ways.
First, during the meiotic divisions of oogenesis, cytokinesis is unequal, with almost all the cytoplasm monopolized
by a single daughter cell, the secondary oocyte. This large cell can go on to become the ovum; the other products of
meiosis, smaller cells called polar bodies, degenerate. By contrast, in spermatogenesis, all four products of meiosis
develop into mature sperm (compare Figures 46.11 and 46.12).
2. Second, although the cells from which sperm develop continue to divide by mitosis throughout the male′s life, this
is thought not to be the case for oogenesis in the human female (but see the text in Figure 46.11).
Third, oogenesis has long “resting” periods, in contrast to spermatogenesis, which produces mature sperm from
precursor cells in an uninterrupted sequence.