CHAPTER 18
Male Reproductive System
351
Nucleus of
Nucleus of
early spermatid
early spermatid
Nucleus of
early spermatid
Nucleus of
Nucleus of
early spermatid
early spermatid
Nucleus of
early spermatid
Centrioles
Centrioles
Centrioles
Nucleus of
Nucleus of
early spermatid
early spermatid
Nucleus of
early spermatid
Golgi complex
Golgi complex
Golgi complex
Figure 18-5.
Seminiferous epithelium, early spermatid.
EM,
3
17,000
Completion of
meiosis II
by
secondary spermatocytes
produces
spermatids
. These are haploid cells that do not divide but undergo
spermiogenesis
, that is, morphological differentiation into
spermatozoa
. The cells in this image are
early spermatids
that have not
yet acquired many of the specializations of spermatozoa. The interphase nucleus in the center is still spherical, and the chromatin is
not yet highly condensed. The
Golgi complex
, visible in the cell on the
left
, will be the site of development of the acrosomal vesicle
and, ultimately the acrosome, which will form a cap on one side of the nucleus. Note that the plane of section happens to pass
through the central cell’s centrosome with its pair of
centrioles
. One member of the pair will organize the development of the fl
agel-
lum with its axoneme of microtubules. The other centriole will participate in the F
rst cleavage division if the spermatozoan fertilizes
a
secondary oocyte
. This
spermatid
is linked to its cohort spermatids by cytoplasmic bridges, although this is not evident in this
image. Like all cells engaged in spermatogenesis, spermatids are embedded in cytoplasmic processes of Sertoli cells.
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