488
Chapter 14
The result of additional mergings from this point on is that
the urine drains into the kidney’s central cavity, the
renal pel-
vis,
via several hundred large medullary collecting ducts. The
renal pelvis is continuous with the ureter draining that kidney
(
Figure 14–4
).
There are important regional differences in the kidney
(see Figures 14–2 and 14–4). The outer portion is the
renal
cortex,
and the inner portion the
renal medulla.
The cortex
contains all the renal corpuscles. The loops of Henle extend
from the cortex for varying distances down into the medulla.
The medullary collecting ducts pass through the medulla on
their way to the renal pelvis.
All along its length, each tubule is surrounded by capil-
laries, called the
peritubular capillaries.
Note that we have
Figure 14–2
Basic structure of a nephron. (a) Anatomical organization. The macula densa is not a distinct segment, but a plaque of cells in the ascending
loop of Henle where the loop passes between the arterioles supplying its renal corpuscle of origin. The outer area of the kidney is called the
cortex and the inner the medulla. Two types of nephrons are shown—the juxtamedullary have long loops of Henle that penetrate deeply into
the medulla, while the cortical nephrons have short (or no) loops of Henle. Note that the efferent arterioles of juxtamedullary nephrons give
rise to long looping vasa recta, while efferent arterioles of cortical nephrons give rise to peritubular capillaries. (b)
See next page.
(a)
Vein
Artery
Vasa recta
Descending
limb
Loop of Henle
Medullary
collecting duct
Cortical
collecting
duct
Cortical nephron
Juxtamedullary nephron
Bowman's
capsule
Glomerulus
Proximal
convoluted
tubule
Distal
convoluted
tubule
Efferent arteriole
Afferent arteriole
Vein
Artery
Macula densa
Renal corpuscle
Peritubular
capillaries
Corticomedullary
junction
Thick
segment of
ascending
limb
Thin
segment of
ascending
limb
M
e
d
u
l
l
a
C
o
r
t
e
x
Urine
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