358
UNIT 3
Organ Systems
Figure 18-12B.
Stage IV seminiferous epithelium.
H&E,
left
3
207;
right
3
747
Stage IV seminiferous epithelium
is shown at low magnif cation (
left
), and a detailed representation oF the region is indicated by the
box (
right
). Stage IV diFFers From stage III mainly in the progression oF the generation oF early spermatids (in stage III) to intermediate
spermatids (in stage IV). Stage IV has the Following composition: (1)
Intermediate spermatids
with diamond-shaped or irregular nuclei;
(2) one generation oF primary spermatocytes in
pachytene
oF prophase I; (3) a separate generation oF primary spermatocytes at an
early (
prepachytene
) stage oF prophase I; and (4)
Type A spermatogonia
in the basal compartment.
Figure 18-12A.
Stage III seminiferous epithelium.
H&E,
left
3
207;
right
3
747
Stage III seminiferous epithelium
is shown at low magnif
cation (
left
), and a detailed representation oF the region is indicated by
the box (
right
). Stage III has a similar composition oF spermatogenic cells as that oF stage II, except For the absence oF the detaching
spermatozoa at the surFace and the added presence oF a new generation oF primary spermatocytes near the basement membrane
(not readily apparent). This stage is characterized by the Following: (1) There is an absence oF
detaching spermatozoa
, which have
been released into the lumen to be suspended in testicular fl
uid and transported along the genital ducts. (2)
Early spermatids
with
round nuclei have moved to the surFace oF the epithelium. (3) There is the continued presence oF a generation (cohort) oF
primary
spermatocytes
in the pachytene stage oF prophase I. (4) A new generation oF primary spermatocytes has moved From the
basal com-
partment
into the
adluminal compartment
, although they are diFf
cult to distinguish. Compartments are created by
tight junctions
oF
neighboring
Sertoli cells
. The
basal compartment
is situated on the basement membrane side oF the tight junctions between
Sertoli
cell
s, and it contains spermatogonia. The
adluminal compartment
is situated above the junctions and toward the lumen and contains
spermatocytes and spermatids. The tight junctions establish a
blood-testis barrier
that prevents immunoglobulins From entering the
adluminal compartment. Newly Formed primary spermatocytes are liFted From the basal compartment and into the adluminal com-
partment by outgrowth oF processes extended From the local Sertoli cells.
Early
Early
spermatids
spermatids
Early
spermatid
Pachytene
Pachytene
primary
primary
spermatocytes
spermatocytes
Pachytene
primary
spermatocyte
Sertoli cell
Sertoli cell
Sertoli cell
Lumen
Spermatogonium
Spermatogonium
Spermatogonium
Basal
Basal
compartment
compartment
Basal
compartment
Basement
Basement
membrane
membrane
Basement
membrane
Adluminal
A
d
lu
m
in
a
l
compartment
c
o
m
p
a
r
t
m
e
n
t
Adluminal
compartment
A
Prepachytene
Prepachytene
primary
primary
spermatocyte
spermatocyte
Prepachytene
primary
spermatocyte
Lumen
Lumen
Lumen
Intermediate
Intermediate
spermatids
spermatids
Intermediate
spermatids
Pachytene
Pachytene
primary
primary
spermatocytes
spermatocytes
Pachytene
primary
spermatocytes
Spermatogonium
Spermatogonium
Spermatogonium
Sertoli cell
Sertoli cell
Sertoli cell
B
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