Shoulder

Brachium

Antebrachium

Facial and Masticatory Muscles

Thorax and Heart

Brain

Body Wall

Hip and Thigh

Shank and Foot

Digestive System

Urinary and Reproductive Systems

Hip and Tail

Urinary and Reproductive Systems of the Rabbit (Oryctolagus cuniculus)

Photos and text by Alexandra Sardi and Janelle Cooper

Dissection Notes:

The dissection of the urogenital system was difficult and time consuming.  The testes in the rabbit are abdominal and covered with hair, which must be removed very carefully.  Furthermore, the anus and penis are found in a single protuberance, which is also covered with hair.  The hair must be removed with extreme caution, as it is very easy to accidentally cut into one of the structures.  We would suggest having a razor or other means of shaving the rabbit, as this would have made our dissection a lot simpler.  Dissecting the kidneys was the simplest part of the dissection and involved simply making a frontal section and exposing the renal pelvis and renal papilla since they had already been exposed in the digestive system lab.  The kidneys were embedded in fat but were not suspended by a mesentery. They are covered by peritoneum on the dorsal abdominal wall.  This is called being retroperitoneal, or behind the peritoneum. 

Description:

Once we removed the digestive system, the kidneys, aorta and vena cava were in plain view. We freed the kidney from the peritoneum and sectioned one horizontally and one vertically.  We identified one renal papilla per kidney and one renal pelvis. The vena cava caudalis ran along the midline, between the kidneys and drained them through the right and left renal veins.  The aorta abdominalis ran dorsal to the vein and supplied the kidneys through the right and left renal arteries.  We followed the ureter to the bladder, which was cranial to the ductus deferens and glandula vesicularis. We also found the urethra, which empties the bladder.  Proceeding caudally, we located the scrotum. It hangs below the pelvic wall and is anterior to the penis (2).  The rabbit was the only eutherian mammal in class to have the testes anterior to the penis.  While common in marsupials, and present in our class’s Monodelphis, it is not usually observed in eutherian mammals.  Cranial to the scrotum we identified relatively large right and left cremaster muscles.  We also found the spermatic cord, containing the internal spermatic artery and vein and the ductus deferens.    The ducti deferens pass through an opening in the body wall called the inguinal canal.  The ductus deferens unites with the urethra and travels to the tip of the penis (2). The rabbit also has a seminal vesicle ventral to the rectum and caudal to the ductus deferens (2).   The bulbourethral, or Cowper’s glands, are bean shaped glands located on either side of the body of the penis (3).   In our dissection we accidentally cut a piece of the penis but the rabbit’s penis does not have any spines or projections according to the literature, nor does it contain a baculum (3).

Discussion:

The rabbit’s kidneys were normally placed, shaped and sized.  The internal part of the kidney also seemed normal when compared to what we could find in the literature. 

In our dissection we discovered that rabbits do have a scrotum.   The testes are usually abdominal but descend into the scrotum during mating season.  It is unclear why some animals have evolved a scrotum and others have not (4). Nevertheless, we do know that lagomorphs undergo huge temperature changes, such as from the burrow to the hot sun, and it makes sense that they should have a scrotum to help maintain the temperature. This would especially be the case during mating season.  Rabbits also have a pampiniform plexus, a countercurrent exchange system, which aids in maintaining a constant temperature (3).

We found large right and left cremaster muscles.  We expected this due to the fact that the rabbits retract their testes into their abdomen. 

While we had a male, we wanted to note a few things about female reproductive anatomy.  Females have a single vagina, which is anterior to the rectum and posterior to the clitoris (2).  The urethra empties directly into the vagina, creating the urogenital sinus.  The female has two uteri and is capable of superfetation, or carrying two litters in different stages of development. This is possible because rabbit’s ovulate upon copulation and different ovaries can ovulate at different times.  Hence, the rabbit can be pregnant with a different litter in each uterus (4). 

References:

1. McLaughlin C.A., Chiasson R.B., Laboratory Anatomy of the Rabbit, McGraw-Hill, New York: 1990.

2. Wingerd, Bruce D., Rabbit Dissection Manual, Johns Hopkins University Press, Baltimore: 1985.

3. Kent, George C. and Carr, Robert K., Comparative Anatomy of the Vertebrates. McGraw-Hill, New York: 2001.

4. Kardong, Kenneth V., Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, New York: 2002.