228
UNIT 3
Organ Systems
Figure 12-5A.
Renal corpuscle, renal cortex.
The
renal corpuscle
is the site of blood F ltration and
initial production of urine. The main components of a
renal corpuscle are a tuft of capillaries called the
glom-
erulus
and a surrounding sac, the
Bowman capsule
. The
area of the renal corpuscle through which the arterioles
pass into and out of the glomerulus is called the
vascular
pole
. The surfaces of the capillaries of the glomerulus are
covered by podocytes, which make up the
visceral layer
of the Bowman capsule. The outer wall of the renal cor-
puscle is a simple squamous epithelium called the
parietal
layer
of the Bowman capsule. ±luid is F ltered from the
blood in glomerular capillaries into the space between
the two layers, the
Bowman space
. ±luid exits through
the
urinary pole
to enter the
proximal convoluted
tubule
. There are phagocytic cells called
mesangial cells
(or
intraglomerular mesangial cells
) in the interstitial tis-
sue between the glomerular capillaries. Similar cells are
called
extraglomerular mesangial cells
when located at
the vascular pole of the corpuscle.
Juxtaglomerular cells
in the walls of afferent arteriole are modiF ed smooth
muscle cells that secrete
renin
in order to regulate blood
pressure. The
macula densa
of the distal tubule is located
between the afferent and the efferent arteries.
T. Yang & D. Cui
Juxtaglomerular cells
Afferent arteriole
Intraglomerular
mesangial cell
Bowman space
(urinary space)
Urinary pole
Proximal convoluted tubule
Parietal layer
of
Bowman capsule
Vascular pole
Nucleus of
podocyte cell
Efferent arteriole
Visceral layer
(podocytes) of
Bowman capsule
Macula densa
of the distal tubule
Extraglomerular
mesangial cells
A
Figure 12-5B.
Renal corpuscle, glomerulus and Bowman capsule.
H&E,
3
402; insets (
left
)
3
921; insets (
lower right
)
3
183
A
glomerulus
housed within the
Bowman capsule
is shown here. The lighter space between these two structures is the
Bowman space
.
The
upper left small inset
shows the
macula densa
, a row of columnar cells that are densely packed together. This is a special sensory
structure of the distal tubule as it passes close to the afferent and efferent arterioles at the vascular pole (±ig. 12-5A). The macula
densa plays a role in monitoring ionic content and volume of the F ltrate. The
lower left small inset
shows the Bowman space between
the glomerulus and the parietal layer of the Bowman capsule. The
lower right inset
shows the
urinary pole
.
Squamous cell
Squamous cell
of the parietal layer
of the parietal layer
Podocyte
Podocyte
Squamous cell
of the parietal layer
Podocyte
Parietal layer
of
Parietal layer of
Bowman capsule
Bowman capsule
Parietal layer
of
Bowman capsule
Urinary
Urinary
pole
pole
Urinary
pole
Afferent/efferent
Afferent/efferent
arteriole
arteriole
Afferent/efferent
arteriole
Macula densa
Macula densa
of distal tubule
of distal tubule
Macula densa
of distal tubule
Distal
Distal
convoluted tubules
convoluted tubules
Distal
convoluted tubules
Glomerulus
Glomerulus
Glomerulus
Bowman
Bowman
space
space
Bowman
Bowman
space
space
Bowman
space
Bowman
space
Proximal
Proximal
convoluted tubules
convoluted tubules
Proximal
convoluted tubules
Proximal
Proximal
convoluted
convoluted
tubules
tubules
Proximal
convoluted
tubules
Columnar cells of macular densa
Columnar cells of macular densa
Columnar cells of macular densa
Luman of the
Luman of the
distal tubule
distal tubule
Lumen of the
distal tubule
Glomerular
Glomerular
capillaries
capillaries
Glomerular
capillaries
Visceral layer of
Visceral layer of
Bowman capsule
Bowman capsule
Visceral layer of
Bowman capsule
B
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