The Kidney Is a Complex Filter
Internally, each kidney itself has two main regions: the
renal cortex and the renal medulla (Figure 15.2). The
cortex receives most of the blood supply, and the medulla
contains tubules that collect and concentrate the fluid
that becomes the urine.
Urine formed in the kidney drains into a large, funnel-
shaped cavity called the renal pelvis. The rim of the renal
pelvis contains cuplike structures called major and minor
calyces (KAL-i-sez; the singular form is calyx). Urine
flows from several ducts within the kidney into a minor
calyx. From there, it moves through a major calyx into the
renal pelvis, which connects to a ureter. Water and solutes
in the fluid that drains into the renal pelvis are excreted,
or eliminated from the body.
InSight
I n t e r n a l s t r u c t u r e o f t h e k i d n e y
F ig u r e 1 5 . 2
Renal cortex is a
light red outer
region.
Renal medulla is a dark —
brown inner region
composed of cone shaped
sections called renal
pyramids.
Renal pyramids
Renal columns are
an extension of the
cortex that divide the
medulla into renal
pyramids.
Renal pelvis is a funnel
shaped cavity that
drains urine into the
ureter. It consists of a
major calyx and
minor calyx.
Nephron
Renal capsule is a
connective tissue
sheath that maintains
the kidneys shape and
protects it.
Path of Urine
Drainage
Collecting duct
Minor calyx
Major calyx
J
Renal pelvis
Urinary bladder
a.
Frontal section of right kidney showing path of urine drainage
440 CHAPTER 15
The Urinary System and Fluid, Electrolyte, and Acid-Base Balance
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