Fig. 108.--_a_, renal artery; _b_, renal vein; _c_, ureter.
Fig. 109.--_a_, medullary portion; _b_, cortical portion; _c_,
papilla; _d_, pelvis; _e_, renal artery; _f_, renal vein; _g_,
ureter.]
The kidneys of the cat are compact (i.e., not lobulated) and have the
usual kidney or bean form. They lie in the abdominal cavity, one on
either side of the vertebral column, against the dorsal body wall, in
the region between the third and fifth lumbar vertebræ. The right kidney
is one or two centimeters farther craniad than the left, and the long
axes of the two converge craniad a little. Each is covered by peritoneum
on its ventral surface only (i.e., it is retroperitoneal). At the
border of the kidney, where the peritoneum passes from it to the body
wall, there is an accumulation of fat, which is most abundant at the
cranial end of the kidney. Within the peritoneal investment the kidney
is enclosed in a special loose fibrous covering, the =capsule= or
=tunica fibrosa=, which is continuous with the fibrous coat of the
ureter and pelvis. In the middle of the median border of each kidney is
a notch, the =hilus=. It gives exit to the ureter (Fig. 108, _c_) and
renal veins (_b_), and entrance to the renal artery (_a_). On the
ventral surface of the kidney within the capsule are seen grooves
radiating from the hilus. They contain blood-vessels. If the substance
of the kidney is sliced away parallel to the ventral surface for some
distance (Fig. 109), there is exposed a cavity, the =sinus=, which lies
near the medial border and the opening of which is the hilus. It
contains the pelvis (_d_) (the expanded beginning of the duct of the
kidney), and also renal vessels (_e_ and _f_) with their branches. These
structures are enclosed in fat, which fills the remainder of the sinus.
Upon opening the pelvis the kidney substance is seen to project into it
in the form of a cone, the =papilla= (_c_), the apex of which is
directed mediad. On the apex of the papilla are the numerous openings of
the uriniferous collecting-tubes, some of them opening at the bottom of
an apical depression of the papilla.
In a section made parallel to the ventral surface and in the median
plane, the substance of the kidney is seen to consist of a peripheral
darker and more granular =cortical portion= (Fig. 109, _b_), and of a
central, lighter, less granular =medullary portion= (_a_). Both portions
are marked by lines which converge to the apex of the papilla (_c_).
THE URETER (Fig. 108, _c_; Figs. 111 and 112, _b_).--The duct of the
kidney begins as the =pelvis= (Fig. 109, _d_), a conical sac the base of
which encloses the base of the papilla. From the apex of the papilla the
urine passes into the pelvis. The outer wall of the pelvis is continuous
with the capsule of the kidney. At the hilus the pelvis narrows to form
the =ureter= (Fig. 109, _g_). The ureter passes caudad in a fold of
peritoneum which contains fat. Near its caudal end it passes dorsad of
the vas deferens (Fig. 111, _c_), turns ventrocraniad, and pierces the
dorsal wall of the bladder (Fig. 111, _a_) obliquely near the neck. On
the inside of the bladder the openings of the ureters appear as pores
about five millimeters apart, and each is surrounded by a white,
ring-like elevation of the surface.
THE BLADDER. VESICA URINARIA.--The bladder (Fig. 111, _a_) is
pear-shaped. It lies in the abdominal cavity between its ventral wall
and the rectum and a short distance craniad of the pubic symphysis.
Caudad it is continued into a rather long, narrow =neck= (_f_) which
passes dorsad of the symphysis to the pelvic cavity.
The bladder is covered by peritoneum and is held in place by its neck
and by three folds of the peritoneum. One of these passes from its
ventral wall to the linea alba and is the =suspensory= ligament. Two
others pass one from each side of the bladder to the dorsal body wall at
the sides of the rectum. They are the =lateral= ligaments of the
bladder. They form the walls of a partly isolated peritoneal pocket into
which the rectum passes; this pocket opens craniad into the peritoneal
cavity. The wall of the bladder is composed of an internal epithelium, a
layer of plain muscle-fibre bundles which cross one another in various
directions, and the external peritoneal layer.
SUPRARENAL BODIES. GLANDULÆ SUPRARENALES.--The suprarenal bodies are two
ovoid bodies about a centimeter in the longest diameter, lying
craniomediad of the kidneys, but usually not touching them. In a fresh
condition they are of a pinkish or yellow color. They are usually
imbedded in fat and are covered by peritoneum on their ventral surface.
They have no duct and are of uncertain function.