UROGENITAL SYSTEMS
The major organs of the urinary system are kidneys. The bean-shaped kidneys in
rabbits, like all amniotes, are metanephric kidneys and are located against the dorsal wall
of the peritoneal cavity. They will often be surrounded by fat that can be carefully
removed along with connective tissue. On the medial edge, you can see an indentation
(hillus) where the renal artery and vein enter the kidney and the ureter drains the
kidney and carries urine to the urinary bladder that is emptied via the urethra. The
adrenal glands on top of each kidney produce steroids and aldosterone. Remove one
of the kidneys and a frontal section exposes the following sections (with major
associated structure or location): the outer renal cortex (nephrons), beneath cortex =
renal medulla (loop of henle), renal papilla (apex of medulla), renal pelvis
(expanded portion of ureter), and renal sinus (collecting tubules empty).
The female genital system consists of the ovaries (eggs develop and hormones) that
are paired oval structures slightly caudal to the kidneys. Ovulation occurs when eggs
are discharged from the ovaries, through part of the body cavity and into oviducts.
These carry the eggs to the uterus. In rabbits (and rodents), the uterus is considered
duplex type where the lower uteri remain distinct and separate until they join at the
vagina. In cats, the lower ends of the uteri have partially fused to form a bicornate
uterus, and primates have a completely fused uterus. The rabbit uteri converge and
enter the vagina (end reproductive tract) directly. The vagina continues through the
pelvic canal, between the urethra and large intestine, uniting with the urethra in the
urogenital canal. The common canal to the body surface is known as the vaginal
vestibule and a large clitoris is easily located near the opening by cross-sectioning the
vagina and vaginal vestibule. Rabbits also have a pair of elongate anal glands on the
lateral surface of the vestibule.
The male genital system includes the testes (produce sperm) that descent into the
scrotum (sac). The scrotum in cats and humans is caudal to the ventral surface of the
pelvis and the penis. In rabbits, the scrotum is cranial to the penis - a condition found
only in lagomorphs and marsupials. The scrotum is part of a thermoregulatory system
because the higher core body temperature inhibits the transformation of speratids into
tailed spermatozoa. Open the scrotum and find the epididiymis - a band like structure
of coiled tubules on testis. The ductus deferens exits the caudal end of the
epididymis, passes through the abdominal wall, loop over the ureter, join together and
enter the urethra (in cats they enter separately). The prostate gland (makes seminal
fluid) marks this urethra entry in cats but in rabbits, the vesicular gland contains the
prostate. The penis encloses the urethra outside the pelvic region. A cross section of
the glans penis (free end) can reveal a small bone - the baculum. The elongate anal
glands are on either side of the rectum near the anus.