Maintenance of the Body
Each nephron consists of a
All of the renal corpuscles are located in the renal cortex, while
the renal tubules begin in the cortex and then pass into the me-
dulla before returning to the cortex.
consists of a tuF of capillaries called a
ball of yarn) and a cup-
shaped hollow structure called the
). Te glomerular capsule completely sur-
rounds the glomerulus, much as a well-worn baseball glove en-
closes a ball, and is continuous with its renal tubule.
Te endothelium of the glomerular capillaries is
(penetrated by many pores), which makes these capillar-
ies exceptionally porous. Tis property allows large amounts of
solute-rich but virtually protein-free ﬂuid to pass from the blood
into the glomerular capsule. Tis plasma-derived ﬂuid or
is the raw material that the renal tubules process to form urine.
Te glomerular capsule has an external
parietal layer and a visceral layer that clings to the glomerular
is simple squamous epithelium (±igures 25.5,
25.8, and 25.10a). Tis layer contributes to the capsule structure
but plays no part in forming ﬁltrate.
artery to reach the kidney. Tese sympathetic vasomotor ﬁbers
regulate renal blood ﬂow by adjusting the diameter of renal arte-
rioles and also inﬂuence the formation of urine by the nephron.
Check Your Understanding
Roger is hit in the lower back by an errant baseball. What
protects his kidneys from this mechanical trauma?
From inside to outside, list the three layers of supportive
tissue that surround each kidney. Where is the parietal
peritoneum in relation to these layers?
The lumen of the ureter is continuous with a space inside the
kidney. This space has branching extensions. What are the
names of this space and its extensions?
For answers, see Appendix H.
Describe the anatomy of a nephron.
ronz) are the structural and functional units of
the kidneys. Each kidney contains over 1 million of these tiny
blood-processing units, which carry out the processes that form
. In addition, there are thousands of
, each of which collects ﬂuid from several nephrons
and conveys it to the renal pelvis.
(a) Frontal section illustrating major blood vessels
Cortical radiate artery
Nephron-associated blood vessels
(see Figure 25.7)
Inferior vena cava
Cortical radiate vein
or vasa recta
(b) Path of blood flow through renal blood vessels
Blood vessels of the kidney.