KIDNEYS
Each kidney has a concave
medial border, the hilum—where nerves enter, the ureter exits, and blood
and lymph vessels enter and exit—and a convex lateral surface, both covered by
a thin fibrous capsule (Figure 1). The expanded upper end of the ureter,
called the renal pelvis, divides into two or three major calyces. Smaller
branches, the minor calyces, arise from each major calyx. The area
surrounding the calyces, called the renal sinus, usually contains
considerable adipose tissue.
Figure 1.
Each kidney is
bean-shaped, with a concave hilum where the ureter and the renal artery and
veins enter. The ureter divides and subdivides into several major and minor calyces,
around which is located the renal sinus containing adipose tissue. Division of
the parenchyma into cortex and medulla can also be seen grossly. Attached to
each minor calyx is a renal pyramid, a conical region of medulla delimited by
extensions of cortex. A renal pyramid with associated cortex constitutes a
renal lobe. The cortex and hilum are covered with a fibrous capsule.
The kidney has an outer cortex
and an inner medulla (Figures 1 and 2). In humans, the renal
medulla consists of 8–15 conical structures called renal pyramids, which
are separated by cortical extensions called renal columns. Each
medullary pyramid plus the cortical tissue at its base and along its sides
constitutesa renal lobe (Figure 1).
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