Cat urogenital system
Photo and Text: Kyungmin Shin
The urogenital system originates from a single system in the early development, but it differentiates into the urinary tract and the reproductive system in the adult. This cat was a fixed male. Therefore, since its testes were surgically removed, it could not produce testosterone. Without testosterone, I expected the penis to be reduced in size, and the erectile tissue to be degraded in the absence of testosterone after castration. As a male cat, obviously it does not have the female reproductive system such the uterus, ovaries and fallopian tubes. Not having the uterus allow it to havea a larger bladder, simply because there is more room for it.
Only the outline of the kidneys is visible after removing the gastrointestinal
tract, because they are heavily embedded in fat for protection. Healthy animals
are supposed to have lots of fat around kidneys. Removing the fat around the
kidneys requires caution, because it is easy to accidentally remove the ureters
with the fat. The ureters are light in color, and are deeply embedded in the
fat, which makes it difficult to distinguish the ureter from the fat just by
looking at it. The ureters are usually elastic and not as soft as the fat, but
as in this cat, sometimes they can become very soft and disintegrate easily.
Thus, the best way to remove the fat around the ureter is to remove the fat
from the kidneys first, and then track the ureter coming out of the kidneys
and follow it down to the bladder.
As soon as the renal fascia, which holds the kidneys loosely in place, is removed,
the kidneys are can be moved around. The kidneys are retroperitoneal, and the
right kidney is anterior to the left. Each kidney is covered by thin fibrous
capsule, and cutting the kidneys in half allows one to see the renal pyramids,
the renal pelvis and other structures within the kidney. The renal pyramids
were very well differentiated in this cat, appearing as dark spots surrounded
by the lighter cortex. Also, in the bisected kidneys, the arteries and veins
are visible in the cortex area if the animal is double-injected.
Following the arteries and veins from the kidney, one can see that the left
renal vein crosses the aorta to reach the left kidney. If the aorta and the
vena cava are followed posteriorly into the pelvic area, they split into several
branches, notably the external and internal iliac arteries and veins. The internal
iliac arteries are the most superficial, and thus are clearly visible dorsal
to the bladder.
The urinary bladder has thick and tough walls, and it seems to be able to expand
to a relatively large size. The urethra exits the urinary bladder and runs posteriorly
to meet the penis. The urethra can be seen more clearly if the pubic symphysis
is cut.
The penis in this cat was very small and extremely difficult to identify. It
is easier to find the erectile tissues and then find a small protrusion from
those tissues. The unique texture of the penis, and it was somewhat darker in
color from the other erectile tissues that surrounds the penis, even though
the penis itself is entirely composed of erectile tissues. The penis had spiny
texture due to the corpora cavernosa. However, since this cat was fixed, its
glands were non-existent or were impossible to find.
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