C h a p t e r 2 4
Structure and Function of the Kidney
601
supply the upper, middle, and lower parts of the kid-
ney. The lobular arteries further subdivide to form the
interlobular arteries at the level of the corticomedullary
junction (Fig. 24-3). These arteries give off branches,
the arcuate arteries, which arch across the top of the
pyramids. Small intralobular arteries radiate from the
arcuate arteries to supply the cortex of the kidney. The
afferent arterioles that supply the glomeruli arise from
the intralobular arteries.
Although nearly all the blood that enters the kidney
flows through the cortex, less than 10% passes into the
medulla and only about 1% moves into the papillae.
Under conditions of decreased perfusion or increased
sympathetic nervous system stimulation, blood flow is
redistributed away from the cortex toward the medulla.
This redistribution of blood flow decreases glomerular
filtration while maintaining the urine-concentrating
ability of the kidneys, a factor that is important during
conditions such as shock.
The Nephron
Each kidney is composed of more than 1 million tiny,
closely packed functional units called
nephrons,
each of
which is capable of producing urine (Fig. 24-4A). Each
nephron consists of a glomerulus, where blood is fil-
tered, and a system of tubular structures where water,
electrolytes, and other substances needed to maintain the
Interlobar
artery
Renal
artery
Ureter
Pyramid
Intralobular
arteries
Arcuate
artery
FIGURE 24-3.
Simplified illustration of the arterial supply
of the kidney. (From Cormack DH. Ham’s Histology. 9th ed.
Philadelphia, PA: J.B. Lippincott; 1987.)
Proximal convoluted tubule
Efferent arteriole
Afferent arteriole
Bowman capsule
Peritubular capillary
Glomerulus
Cortex
Medulla
Cortex
Outer
medulla
Inner
medulla
Outer stripe
Inner stripe
Descending limb
Ascending limb
Loop of Henle
To papilla
A
B
Collecting tubule
Vasa
recta
Distal convoluted tubule
Interlobular vein
Interlobular artery
Juxtaglomerular
apparatus
FIGURE 24-4.
(A)
Nephron showing the glomerular and tubular structures along with the
blood supply.
(B)
Comparison of differences in location of tubular structures of the cortical and
juxtamedullary nephrons.
