Biomedical Engineering Reference
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Fig. 8.2
Anatomical aspect of spermatogenesis in the mouse testis. (
a
) Schematic overview of the
mouse testis. A single seminiferous tubule out of approximately 20, each of which forms loops with
both ends that open into the rete testis, is shown. (
b
) A highly simplified diagram of mouse semi-
niferous tubule topology. As shown by
green dots
, stem cells are scattered throughout the tubule
loops, which do not show apparent overall polarity. (
c
,
d
) Seminiferous tubules and the surrounding
network of vasculature along with the interstitium. The blood vessels (
red
), which are surrounded
by Leydig cells and other types of interstitial cells (
yellow
), form a network between the seminifer-
ous tubules. (
e
,
f
) Scheme of the seminiferous epithelium architecture, corresponding to the area
shown by
rectangles
in (
c
,
d
). (
e
) Representation of the anatomical framework composed of
somatic components, while spermatogenic cells are included in (
f
). See text for details. Panels,
modified from Yoshida (
2008a
)
termed “gonialblasts” (GB) and “spermatogonia” (SG), respectively, as a distinct
entity from GSC. In the mouse, “spermatogonia” is a wider entity defined as
mitotic stages of spermatogenic cells in the mature testis, including chained cells,
single cells and the stem cells.
Upon entering into meiosis, the spermatogenic cells, now designated as sperma-
tocytes translocate to the adluminal compartment across the tight junction, in a
manner not fully understood yet. This is followed by movement toward the lumen
along with the process of meiotic division and the formation of round and elongating
haploid spermatids. As a result, a multilayered organization of differentiating germ
cells appears among the Sertoli cell epithelium [Fig.
8.2f
, see (Russell et al.
1990
)
for detail]. This basic architecture of seminiferous epithelium is found in the entire
circumference and throughout the length of the tubules.
Thus, the microenvironment for the stem cells, which is a yet-to-be-identified
small subpopulation of spermatogonia, is common to that of the basal compartment,
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