CHAPTER 12
Urinary System
239
Figure 12-15A.
Transitional epithelium,
urinary bladder.
EM,
3
7,280
This f gure shows the surFace oF
transitional
epithelium
and the border between the
cells oF the top layer and the underlying
layer. There are many
fl attened vesicles
(membrane vesicles) in the cytoplasm oF
these cells. The vesicles are more numer-
ous close to the apical region oF the cyto-
plasm. These vesicles are Formed From the
surFace membrane when the bladder is in a
relaxed state. It is important to recall that
the surFace oF the transitional epithelium
oF the bladder is highly convoluted when
the bladder is empty (relaxed). This may
create many “pseudovesicles”; most oF the
vesicles
disappear when the surFace oF the
epithelium is stretched and fl attened in the
distended state. The
boxed area
indicates
±igure 12-15B at higher magnif cation.
Flattened
Flattened
vesicles
vesicles
Flattened
vesicles
Border between
Border between
two cell layers
two cell layers
Border between
two cell layers
Junctional
Junctional
complex
complex
Junctional
complex
Fig. 12-14B
Fig. 12-14B
Fig. 12-14B
A
Figure 12-15B.
Transitional epithelium, urinary bladder.
EM,
3
35,753
A higher power view oF the surFace oF the top layer cells in the
transitional epithelium
is shown. The
junction complex
indicates the
border oF neighboring cells.
Tight junctions
(
zonula occludens
) and
desmosomes
(
macula adherens
) can be observed here. The cells
are f lled with
fl attened vesicles
and
tonof laments
.
Flattened
Flattened
vesicles
vesicles
Flattened
vesicles
Tonofilaments
Tonofilaments
Tonofilaments
Tight junction
Tight junction
Tight junction
Desmose
Desmose
Desmosome
Mitochondrion
Mitochondrion
Mitochondrion
B
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