Histology
of
the
Urinary
system
• Urinary
system
consists
of:
o Two
kidneys
o Two
ureters
(connect
the
kidney
to
the
bladder)
o Urethra
(connects
the
bladder
to
the
outside
world)
The
kidney
• Contain
a
concave
medial
border
called
the
hilum.
The
hilum
contains
nerves,
blood,
and
lymph
vessels.
The
ureter
also
exits
here.
• The
renal
pelvis
is
an
expanded
segment
of
the
ureter.
It
joins
the
kidney
at
the
hilum
and
segments
into
2-‐3
major
calyxes,
which
in
turn
segment
into
minor
calyxes.
• The
kidney
contains
two
regions:
o Cortex
(outer,
can
be
distinguished
by
the
renal
corpuscles
that
are
within
it,
as
well
as
the
darker
staining)
o Medulla
(inner,
pale
staining).
This
contains
renal
pyramids
which
opens
into
the
papilla.
There
are
8
-‐10
pyramids
in
a
multilobar
human
kidney.
o Each
cortex
+
medulla
system
is
called
a
lobe.
Humans
are
multilobar.
Guinea
pigs
have
one
lobe
(one
medullary
pyramid
ends
with
one
papilla
and
one
cortex)
, • Cortex:
o Has
projections
into
the
medulla
between
the
pyramids.
These
projections
are
the
renal
coloumns
and
are
CORTICAL
tissue.
o Glomeruli
are
capillary
aggregations
/
tufts
that
are
scattered
throughout
the
cortex.
These
glomeruli,
along
with
Bowmann’s
capsules,
form
the
RENAL
CORPSUCLE.
o Glomeurli
are
basophilic
since
they
have
a
greater
concentration
of
nuclei
than
the
uriniferous
tubules
(aka
a
nephron).
o The
renal
pelvis
empties
into
the
ureter,
they
are
both
lined
by
transitional
epithelium.
This
epithelium
has
distinct
functional
properties:
§ multiple
layers
of
epithelial
cells
which
can
contract
and
expand
§ Can
rearrange
the
layers
/
distention
based
on
how
full
the
bladder
is.
o The
cortex
has
two
segments
that
alternate,
the
cortical
labyrinth
and
the
medullary
rays.
o Cortical
labyrinth:
§ Renal
corpuscles:
• Composed
of
a
glomeurles
(blood
vessels)
that
has
a
parietal
(outer)
epithelium
and
an
inner
visceral
(made
by
podocytes)
epithelium
of
the
Bowmann’s
capsule
.
• The
parietal
epithelium
lines
the
bowmann’s
capsule
and
continues
along
with
the
proximal
convoluted
tubule.
• Urinary
space
/
Bowmann’s
space
is
where
the
primary
urine
is
formed.
This
is
between
the
two
epithelial
layers
of
the
bowmann’s
capsule.
• Vascular
poles
are
where
the
afferent
and
efferent
arterioles
enter
/
exit
the
corpuscle
to
form
the
glomerulus.
• The
urinary
poles
are
the
region
opposite
the
vascular
poles.
These
urinary
poles
are
where
the
bowmann’s
capsule
opens
to
the
PROXIMAL
CONVULUTED
TUBULE
§ Proximal
convoluted
tubule
• Long
length
=
most
abundant
sectioned
tubules
in
the
cortical
labyrinth.
• Simple
cuboidal
epithelium
• Highly
acidophilic
(will
appear
pink
in
H/E)
à
this
is
because
of
high
organelle
content.
• Epithelium
will
give
rise
to
the
visceral
and
parietal
layers
of
the
Bowmann’s
capsule.
• Contain
a
brush
border
/
microvilli
in
the
apical
surface.
• Open
into
the
straight
portion
of
the
proximal
tubule.
of
the
Urinary
system
• Urinary
system
consists
of:
o Two
kidneys
o Two
ureters
(connect
the
kidney
to
the
bladder)
o Urethra
(connects
the
bladder
to
the
outside
world)
The
kidney
• Contain
a
concave
medial
border
called
the
hilum.
The
hilum
contains
nerves,
blood,
and
lymph
vessels.
The
ureter
also
exits
here.
• The
renal
pelvis
is
an
expanded
segment
of
the
ureter.
It
joins
the
kidney
at
the
hilum
and
segments
into
2-‐3
major
calyxes,
which
in
turn
segment
into
minor
calyxes.
• The
kidney
contains
two
regions:
o Cortex
(outer,
can
be
distinguished
by
the
renal
corpuscles
that
are
within
it,
as
well
as
the
darker
staining)
o Medulla
(inner,
pale
staining).
This
contains
renal
pyramids
which
opens
into
the
papilla.
There
are
8
-‐10
pyramids
in
a
multilobar
human
kidney.
o Each
cortex
+
medulla
system
is
called
a
lobe.
Humans
are
multilobar.
Guinea
pigs
have
one
lobe
(one
medullary
pyramid
ends
with
one
papilla
and
one
cortex)
, • Cortex:
o Has
projections
into
the
medulla
between
the
pyramids.
These
projections
are
the
renal
coloumns
and
are
CORTICAL
tissue.
o Glomeruli
are
capillary
aggregations
/
tufts
that
are
scattered
throughout
the
cortex.
These
glomeruli,
along
with
Bowmann’s
capsules,
form
the
RENAL
CORPSUCLE.
o Glomeurli
are
basophilic
since
they
have
a
greater
concentration
of
nuclei
than
the
uriniferous
tubules
(aka
a
nephron).
o The
renal
pelvis
empties
into
the
ureter,
they
are
both
lined
by
transitional
epithelium.
This
epithelium
has
distinct
functional
properties:
§ multiple
layers
of
epithelial
cells
which
can
contract
and
expand
§ Can
rearrange
the
layers
/
distention
based
on
how
full
the
bladder
is.
o The
cortex
has
two
segments
that
alternate,
the
cortical
labyrinth
and
the
medullary
rays.
o Cortical
labyrinth:
§ Renal
corpuscles:
• Composed
of
a
glomeurles
(blood
vessels)
that
has
a
parietal
(outer)
epithelium
and
an
inner
visceral
(made
by
podocytes)
epithelium
of
the
Bowmann’s
capsule
.
• The
parietal
epithelium
lines
the
bowmann’s
capsule
and
continues
along
with
the
proximal
convoluted
tubule.
• Urinary
space
/
Bowmann’s
space
is
where
the
primary
urine
is
formed.
This
is
between
the
two
epithelial
layers
of
the
bowmann’s
capsule.
• Vascular
poles
are
where
the
afferent
and
efferent
arterioles
enter
/
exit
the
corpuscle
to
form
the
glomerulus.
• The
urinary
poles
are
the
region
opposite
the
vascular
poles.
These
urinary
poles
are
where
the
bowmann’s
capsule
opens
to
the
PROXIMAL
CONVULUTED
TUBULE
§ Proximal
convoluted
tubule
• Long
length
=
most
abundant
sectioned
tubules
in
the
cortical
labyrinth.
• Simple
cuboidal
epithelium
• Highly
acidophilic
(will
appear
pink
in
H/E)
à
this
is
because
of
high
organelle
content.
• Epithelium
will
give
rise
to
the
visceral
and
parietal
layers
of
the
Bowmann’s
capsule.
• Contain
a
brush
border
/
microvilli
in
the
apical
surface.
• Open
into
the
straight
portion
of
the
proximal
tubule.
