No abstract

The kidney of Diceros bicornis has about 60 lobes, all appearing peripherally. These are separated by interlobar septa, except for small septal defects through which tubules pass. Renal capsule and interlobar septa are fibromuscular and contain small blood vessels. The kidney is about 65% cortex. It contains about 12.5 x 10(6) glomeruli, which form about 7% of the cortical mass and 4.6% of the renal mass. Diameter of a glomerular capsule is about 244 microns, there being no difference in size across the cortex in these adults. The ureter bifurcates into a cephalic and a caudal, fibromuscular, urothelial-lined conduit, into which open about 23 urothelial-lined infundibula. The common large collecting duct, or tubus maximus, of every lobe opens at the apex of its infundibulum. Two tubi may join into one infundibulum. The tubi and their terminal collecting ducts (of Bellini) are part of the inner medulla. Musculature of conduits and infundibula is largely longitudinal. The calyx may be represented by a circular muscle bundle near the apex of every infundibulum. The large intralobar veins are partly adherent to their infundibulum and calyx and receive arcuate veins via valved orifices. Most branches of the renal artery enter via the interlobar septa. Within a septum they branch again and also supply numerous perforators, which thence enter the cortex. Remaining branches of the renal artery enter cortex directly from without. A fibromuscular scaffolding lies deep to arcuate veins where they contact medulla. Where these veins contact cortical tubules; however, their walls become merely endothelium, like the walls of the interlobular veins.

The manatee kidney is composed of several closely apposed lobes. These are formed by cortical folds (plicae corticales) that completely isolate the medullae, except where the medullae of adjacent lobes are partially fused. The cortex is continuous; its folds usually are separated, but only partially, by interlobar septa extending from the renal capsule. The cortex makes up approximately 57% of renal mass in adults and 68% in the calf. There are about 3 million glomeruli per kidney. The average is somewhat less than that expected of an adult eutherian of equal mass. The glomeruli, however, are large; they form 7.38% +/- 1.33 of cortical mass, which is above that for at least ten unrelated adult eutherians. The number of glomeruli per gram of cortex is considerably greater in the calf than in the adult. The medullae are about 43% of renal mass. The cortico-medullary thickness ratio is 0.08 to 0.24. All terminal collecting ducts open at a crater (cratera cribrosa) of varying depth. Hair-pin loops occur at all levels of medulla, and apparently all loops bend at their thick segment. Cortical loops occur in the medullary rays. Vascular bundles were evident at the cortico-medullary border and thin tubules extended into the medulla from the central ends of the medullary rays (cortical) in seven out of the nine kidneys. The renal pelvis is separated from the central ends of the cortical folds by delicate fascia through which pass the interlobar vessels. There are no fornices and no infundibula. The collagenous tissue of the pelvic wall extends across most of the pelvic surface of the outer medulla.

The kidney of R. unicornis has almost 80 closely apposed lobes, all appearing peripherally. Every lobe, almost enclosed by a collagenous septum, resembles a deformed truncated cone. The pelvis proper is a small pouch which divides into a cephalic and a caudal urothelial-lined fibromuscular conduit. The terminal collecting ducts of every lobe open into a tubus maximus. This is lined by cuboidal cells and otherwise has no wall. There is no papilla. All lobes finally empty through the 18 primary infundibular orifices at the pelvic conduits. A primary fibromuscular infundibulum typically yields a secondary one supplying an adjacent lobe. Two or three lobes can use a common tubus maximus by "convergence" of their medullae. Tubus maximus, terminal collecting ducts and deep outer medulla are embraced by a fibromuscular calyx which is the peripheral extension of an infundibulum and is fused to the outer medulla. There is thus no vault between medulla and calyx. Large intralobar veins are fused to the outer wall of the calyx. The possible significance of this is discussed. The cortex is the only part of a lobe which has contact with infundibulum, pelvic conduits, or pelvis proper. The kidney has about 16 million glomeruli which form 5.8% of the adult's cortical mass. Many adult mammals, from mouse to rhinoceros, fit into the log10-log10 slope relating number of glomeruli per kidney to body-mass. Neonatal rhinos at term have mature glomeruli throughout the cortex. The small size of the glomeruli and the large number per field allow 16 million in an 118-gm kidney.

The kidney of the okapi is of the medullary crest type and is divided transversely into six lobes by encroachments of cortex into medulla. These lobes are demarcated externally by furrows. The collecting ducts open at the apex of the truncated medullary crest. The pelvis part of the kidney, or pars pelvina renis, is the entire inner medulla and is the only part exposed to the pelvic urine. The pelvis has 10 interlobar vascular eminences and extends peripherally along-side the interlobar vessels as 10 fornices. The vascular eminences are buttressed by 12 free-edged semilunar eminences, which form pouches across 12 intervascular eminences. At each pole a vascular eminence supplies blood vessels to a dorsal and a ventral intervascular eminence. The extrahilar portion of the renal vein consists mainly of a thick coat of longitudinal muscle. In the renal sinus this heavy muscular coat is absent. The tributaries of this vein open via conspicuous nonmuscular valves. The cortex is about 85% of the renal mass and has about 2.89 X 10(6) glomeruli, which form 4.85% of the cortical mass. The filtering surface of a glomerulus is 0.088 mm2, making the total filtering surface of one kidney 0.219 m2. The number of glomeruli per kidney falls into the line which relates number of glomeruli to adult body weight from mouse to elephant and is expressed by log N = 0.59 log W + 3.2 or by N - 1.585W0.59 where N is the number of glomeruli in one kidney and W the adult body weight.

No abstract

This study focuses on certain aspects of the renal structure of the giraffe, with some implications as to its function. About 4,000 collecting ducts open at the truncated end of a curved crest that juts into the renal pelvis as the inner medulla (IM). Extensions of the pelvis pass between the medullary (MP) and vascular (VP) processes almost to the corticomedullary border. The MPs contain an IM and an outer medulla (OM) containing clusters of capillaries (vascular bundles). The VPs contain the interlobar arteries and veins. All of the IM and almost all of the OM, with its vascular bundles, are bathed with pelvic urine. The cortex comprises 63% of the parenchyma. The OM has nine times the mass of the IM. The IM comprises 4% of the parenchyma. The ratio of mass of the adult cortex to the medulla is 1.7:1.0, and the number of glomeruli per kidney is 6.6 ϫ 10 6 . Glomerular mass is 6.2-6.7% of renal mass in the adult and 5.2% in the 6-month-old calf. The dimensions of the glomerular capsules are the same across the thickness of the cortex. Every terminal collecting duct drains an estimated 1,650 nephrons. In the adult giraffe the ratio of thickness of the muscularis of the main renal artery (RA) to its diameter is 0.117 (right RA) and 0.132 (left RA). These ratios are close to those in rhinoceros and ox but greater than in man. The visceral arteries (celiac, anterior mesenteric, and renal) have about the same muscularis : diameter ratio. Giraffes have arterial hypertension, but atherosclerosis is apparently absent and serum lipid fractions are low. Anat Rec 267: 94 -111, 2002.

This is probably the first description of the renal anatomy of the pigmy hippopotamus. The observations were made with dissecting and transmitted light microscopes. Nephrons were micro‐dissected from macerated portions of the kidney. The apex of the renal loops is always at the wide helicoidal portion of the nephron and occurs in all zones but especially in the outer zone of the medulla. The kidney is the branched tubus maximus type, similar to that of the Nile hippopotamus. Distinguishing features are indicated and discussed.