CHAPTER 18
Male Reproductive System
359
Figure 18-13A.
Stage V seminiferous epithelium.
H&E,
left
3
207;
right
3
747
Stage V seminiferous epithelium
is shown at low magnif
cation (
left
), and a detailed representation oF the region is indicated by
the box (
right
). In this example, stage V has newly developed late spermatids and two generations oF primary spermatocytes. Stage
V is characterized by the Following: (1) There are no early or intermediate spermatids; only
late spermatids
are present. The cyto-
plasm oF each late spermatid extends From the sharply pointed nucleus toward the lumen. (2) Two generations (both
pachytene
and
p repachytene
) oF
primary spermatocytes
are present. (3)
Type A spermatogonia
are present, as always, in the basal compartment.
Basement
Basement
membrane
membrane
Basement
membrane
Prepachytene
Prepachytene
primary
primary
spermatocyte
spermatocyte
Prepachytene
primary
spermatocyte
Late
Late
spermatids
spermatids
Late
spermatids
Pachytene
Pachytene
primary
primary
spermatocyte
spermatocyte
Pachytene
primary
spermatocyte
Spermatogonium
Spermatogonium
Spermatogonium
A
Spermatogonium
Spermatogonium
Spermatogonium
Secondary
Secondary
Secondary
spermatocytes
spermatocytes
spermatocytes
Primary
Primary
spermatocytes
spermatocytes
Primary
spermatocytes
Lumen
Lumen
Lumen
(in metaphases)
(in metaphases)
(in metaphases)
B
Figure 18-13B.
Stage VI seminiferous epithelium.
H&E,
left
3
207;
right
3
747
Stage VI seminiferous epithelium
is shown at low magnif
cation (
left
), and a detailed representation oF the region is indicated by the
box (
right
). The most characteristic Feature oF stage VI is the presence oF
metaphases
oF either
primary
or
secondary spermatocytes
,
which are present only in this stage. Interphase secondary spermatocytes also occur in stage VI, but these are rarely apparent. The
characteristics at this stage are as Follows: (1)
Late spermatids
are present at the epithelium near the lumen. (2) Dividing
sperma-
tocytes
with their chromosomes clumped in the center oF the cytoplasm. (3) A separate generation oF primary spermatocytes in
prophase
is present, although they are not easily distinguished. (4)
Type A spermatogonia
are present. This is a very active stage
during which each member oF the older cohort oF primary spermatocytes completes the f
rst meiotic division to produce two second-
ary spermatocytes, and, in a very short time, each secondary spermatocyte completes the second meiotic division to produce two
spermatids.
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