Besides the liver, the other organ with a major role in elimination is the kidney. With a rich blood supply - the kidneys constantly receive approximately one-fourth the heart output - they filter the blood and eliminate the waste it contains, including the pigments derived from hemoglobin, urea, creatinine, the products of hormonal breakdown, and substances of external origin (xenobiotic substances). Since this filtration also leads to the loss of certain precious elements (glucose, sodium, calcium, amino acids, etc., and even water) the kidneys selectively sort and recover the desired elements after the formation of glomerular filtrate.
The basic unit in which urine is formed is a highly folded tube called the nephron. The kidneys consist of nearly one million nephrons. Each nephron is supplied by a small capillary that undergoes passive filtration: Blood pressure causes water and all the elements that can pass through the pores of the filter to leave the capillaries. This region is called the glomerular chamber. In a cat weighing 3 kg, it forms 6 to 12 ml of glomerular filtrate per minute, or approximately 8 to 16 liters per day, although its blood volume is a mere 200 ml. This shows the significance of the reabsorption functions based in the nephron. Thanks to a series of specialized carriers, the walls of the various parts of the nephron constantly transfer precious elements from the urine to the blood. These transfers also lead to the passage of water and concentrate the urine. The cat is a big water saver: in the event of dehydration, it can produce highly concentrated urine (over five times more concentrated than blood). Under normal conditions, the total quantity of urine produced per day is 10 to 15 ml per kg of body weight.
- Quantity: 10 to 15 ml/kg of weight/day.
- pH: 5 to 7.
- Density: 1,018 to 1,040.
- Urea: 800 to 4,000 mg/kg of weight/day.
- Creatine: 12 to 20 mg/kg of weight/day.
Urine is carried from the kidneys to the bladder by the ureters. The cat's bladder has such a large capacity that a cat can easily go over twelve hours without urinating. During urination, urine is expelled from the body through the urethra, a passageway that is different in males and females. In males, it opens at the tip of the penis, which faces backward during rest. As before defecation, prior to urination the cat seeks an appropriate spot and assumes a characteristic posture. Then a reflex is triggered, and the bladder is completely emptied. Under some conditions, cats can release small quantities of urine in various places. This activity, called urine marking, is linked to the cat's social behavior and governs the relationships between individual cats. Castrated animals usually do not display this behavior.
Site et CRM réalisé par ActivSoft Zenengo
Log in
