Chapter 25
The Urinary System
957
25
bacteria (traveling from other infected sites) that lodge and
multiply in a kidney.
In severe cases of pyelonephritis, the kidney swells, abscesses
form, and the pelvis fills with pus. Untreated, the kidney may be
severely damaged, but antibiotic therapy can usually treat the
infection successfully.
Blood and Nerve Supply
Trace the blood supply through the kidney.
Te kidneys continuously cleanse the blood and adjust its com-
position, so it is not surprising that they have a rich blood sup-
ply. Under normal resting conditions, the large
renal arteries
deliver one-fourth of the total cardiac output (about 1200 ml) to
the kidneys each minute.
Te renal arteries exit at right angles from the abdominal
aorta, and the right renal artery is longer than the leF because
the aorta lies to the leF of the midline. As each renal artery
approaches a kidney, it divides into five
segmental arteries
(Figure 25.4)
. Within the renal sinus, each segmental artery
branches further to form several
interlobar arteries
.
Renal cortex
Renal medulla
Major calyx
Papilla of
pyramid
Renal pelvis
Ureter
Minor calyx
Renal column
Renal pyramid in
renal medulla
Fibrous capsule
Renal
hilum
(a) Photograph of right kidney, frontal section
(b) Diagrammatic view
Figure 25.3
Internal anatomy of the kidney.
Frontal sections. (For a related image,
see
A Brief Atlas of the Human Body
, Figure 71.)
At the cortex-medulla junction, the interlobar arteries branch
into the
arcuate arteries
(ar
9
ku-āt) that arch over the bases of
the medullary pyramids. Small
cortical radiate arteries
(also
called
interlobular arteries
) radiate outward from the arcuate
arteries to supply the cortical tissue. More than 90% of the blood
entering the kidney perfuses the renal cortex.
Afferent arterioles branching from the cortical radiate arter-
ies begin a complex arrangement of microscopic blood vessels.
Tese vessels are key elements of kidney function, and we will
examine them in the next section when we describe the nephron.
Veins pretty much trace the pathway of the arterial supply in
reverse (±igure 25.4). Blood leaving the renal cortex drains se-
quentially into the
cortical radiate, arcuate, interlobar
, and fi-
nally
renal veins
. (Tere are no segmental veins.) Te renal veins
exit from the kidneys and empty into the inferior vena cava. Be-
cause the inferior vena cava lies to the right of the vertebral col-
umn, the leF renal vein is about twice as long as the right.
Te
renal
plexus
, a variable network of autonomic nerve fi-
bers and ganglia, provides the nerve supply of the kidney and its
ureter. An offshoot of the celiac plexus, the renal plexus is largely
supplied by sympathetic fibers from the most inferior thoracic and
first lumbar splanchnic nerves, which course along with the renal
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