782
UNIT FIVE
kidneys. The antigen-antibody complexes are
deposited in and block the glomerular capillaries,
which become further obstructed as the inF
am-
matory response sends white blood cells to the
region. Capillaries remaining open may become
abnormally permeable, allowing plasma proteins
and red blood cells to enter the urine.
Most glomerulonephritis patients eventu-
ally regain normal kidney function. However, in
severe cases, renal functions may fail completely.
Without treatment, the person is likely to die
within a week or so.
N
ephritis
is an inF
ammation of the kidney.
Glomerulonephritis
is an inflammation
of the glomeruli, and it may be acute or
chronic and can lead to renal failure.
Acute glomerulonephritis
(AGN) usually
results from an abnormal immune reaction that
develops one to three weeks following bacterial
infection by beta-hemolytic
Streptococcus.
As a
rule, the infection is not in the kidneys, but bacte-
rial antigens trigger production of antibodies that
form insoluble immune complexes (see chapter
16, p. 639) that travel in the bloodstream to the
Chronic glomerulonephritis
is a progressive
disease in which increasing numbers of nephrons
are slowly damaged until the kidneys are unable
to function. This condition is usually associated
with certain diseases other than streptococ-
cal infections, and it also involves formation of
antigen-antibody complexes that precipitate and
accumulate in the glomeruli. The resulting inF
am-
mation is prolonged, and ±
brous tissue replaces
glomerular membranes, permanently disabling
the nephrons. Eventually the kidneys fail.
20.2
CLINICAL APPLICATION
Glomerulonephritis
afferent and efferent arterioles of its own glomerulus and
makes contact with them. At the point of contact, the epithe-
lial cells of the ascending limb are tall and densely packed.
These cells comprise a structure called the
macula densa.
Close by, in the wall of the afferent arteriole near its
attachment to the glomerulus, are large, vascular smooth
muscle cells called
juxtaglomerular cells.
Together with the
opening in a renal papilla.
Figures 20.10
and
20.11
show the
parts of a nephron. Clinical Application 20.2 examines glom-
erulonephritis, an infl
ammation of the glomeruli.
Juxtaglomerular Apparatus
At the end of the nephron loop, before it becomes the distal
convoluted tubule, the ascending limb passes between the
Slit pore
Pedicel
Primary process
of podocyte
Slit pore
Primary process
of podocyte
Pedicel
FIGURE 20.9
Scanning electron micrograph of a portion of a glomerulus (8,000×). Note the slit pores between the pedicels.
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