Ferret urogenital system
Photos and Text: Victoria Clayton and Catherine Lenox
We had previously exposed the urogenital system during the dissection of the gastrointestinal tract. Though we could see the kidneys, we had to remove a thick layer of fat, enclosed in fascia called the fibrous capsule [1], to make the urogenital system entirely visible. The fibrous capsule protects the kidneys from damage and is present in all but the most emaciated mammals.
The ferret has two kidneys that are retroperitoneal and located in the sublumbar region. They are bean-shaped and the right kidney is anterior to the left kidney. Each is approximately three centimeters in length. The renal artery, renal vein, and ureter converge at the hilus, where the renal artery enters the kidney and the renal vein and ureter exit the kidney. In each kidney, the renal vein is ventral to the renal artery and drains into the caudal vena cava. The ureter exits the kidney dorsal to the renal vessels and then runs caudally. The ureters carry urine from each kidney to the bladder, passing dorsal to the ovarian vein and ventral to the uterine body.
The bladder is a chickpea-sized sac, approximately one centimeter in diameter and two centimeters in length when empty, and has accordion-like walls. It is the most ventral large structure in the posterior abdomen and is surrounded by vesicouterine pouch. Our specimen's bladder was very firm and muscular. The bladder collects urine from both ureters until it is ready to be expressed. The bladder releases urine through a singe urethra. The urethra originates from the urinary bladder dorsal to the cranial edge of the pelvic symphysis, at the posterior fundus of the bladder, and runs ventral to both the vagina and the rectum.
The ferret uterus is bicornuate, meaning it has two uterine horns. In females that have not had litters, the uterine horns are thin and threadlike [2]. We observed very thick uterine horns, indicating that the female had had multiple litters. Both uterine horns are connected to the body wall by strong folds of peritoneum called the broad ligaments [1,2]. The left and right uterine horns are about four or five centimeters in length and fuse just cranial to the bladder to form the uterine body. The uterine body is dorsal to the bladder and ventral to the rectum.
The ferret had very large mammary glands as well, suggesting that she had recently had a litter and was lactating at the time of her death. The mammary tissue lies between the epidermis and the abdominal muscles, and is surrounded by a large amount of fat. Ferrets have six to ten teats [1]; this particular ferret had eight teats (four pair). Each ovoid mammary gland is approximately 1.5 cm thick, 3 cm long, and 2.5 cm wide at its widest point.
A single pea-sized ovary can be found at the cranial end of each uterine horn. An oviduct encircles each ovary and passes eggs into the uterine horn via a short uterine tube. The uterine tube in the ferret is so short it is almost non-existent and is very difficult to see. We found Graafian follicles on the right ovary. These appear as very small clear bubbles on the edge of the ovary.
After we identified the urogenital structures, we made a horizontal cut through the center of the left kidney and removed the ventral half of the organ. There is a distinct color difference between the outer renal cortex, which is lighter in color and granular in appearance, and the inner renal medulla, which is darker and has a striated appearance. The ferret kidney has a single papilla and renal pelvis that drains into the ureter. Renal arterial branches disperse throughout the medulla and are clearly visible in a cross-section. The kidneys did not appear to be abnormal in any way.
Finally, we cut through the pelvic symphysis to see the urethra and vagina. The pelvic symphysis was ligamentous due to the ferret's recent parturition. Late-term pregnancies cause the pelvic symphysis to dissolve. The symphysis gradually re-ossifies after parturition. We removed medial sections of the pubis to observe the courses of the urethra and vagina.
1. Fox, J.G. 1998. Biology and Diseases of the Ferret (2nd Ed.). Williams & Wilkins, Baltimore.
2. Klingener, D. 1979. Laboratory Anatomy of the Mink (2nd Ed.). William C. Brown, Dubuque, Iowa.
to Comparative Mammalian Anatomy
to mammalian urogenital systems