Page 547 - Anatomy and Physiology of Farm Animals, 8th Edition

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external iliac vein with the caudal renal nephrotoxic (damaging to the kidneys)
VetBooks.ir portal vein and the junction of the cranial may be more so when they are first dis-
renal portal vein with the renal vein, con-
tributed undiluted to the kidneys via the
trol blood flow into the renal portal sys-
As in mammals, avian kidneys are com-
tem. Studies suggest that the autonomic renal portal system.
nervous system differentially regulates posed of nephrons that perform glomerular
blood flow through the renal portal system filtration, selective tubular reabsorption,
with dual control of these valves (epineph- and selective tubular secretion in the pro-
rine causes the valves to open and acetyl- cess of urine formation. However, avian
choline causes the valves to close). The kidneys contain two different types of
presence of the renal portal system is nephrons, and one type is markedly differ-
used as a justification for avoiding the ent in structure compared to nephrons of
caudal body as a site for injection of mammalian kidneys. This unique type of
medications in birds. One reason for nephron is termed a reptilian‐type (RT)
this avoidance is that the drugs may be nephron and is similar to those found in
more rapidly excreted when injected kidneys of reptiles. Renal corpuscles of RT
here than is desirable due to their nephrons are found in the lobules of avian
being immediately transported to and kidneys, and a renal tubule connects each
removed by the kidney. Another con- renal corpuscle to a collecting duct also
cern is that drugs that are potentially found in the lobule (Fig. 30‐10). However,

Central vein Collecting duct
Reptilian nephrons

Mammalian nephrons
Peritubular
capillaries
Renal portal vein (PTC)
(blood to PTC)

3
Arterial supply
Central vein
Collecting duct
Arterial supply Renal portal vein
(blood to PTC)
Collecting ducts

2
Medullary cone

1

Ureteral branch

Figure 30-10. Location of mammalian and reptilian type nephrons within a lobule of a typical avian
kidney. Renal portal veins serve as a secondary blood supply to peritubular capillaries. Source: Reece,
2015. Reproduced with permission of John Wiley & Sons, Inc.