1468 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



lumbar splanchnic NER\ES. Direct branches to the 

 renal plexus may arise both from the first and second 

 lumbar ganglia, or from the adjacent portions of the 

 sympathetic trunk. These branches are inconsistent, 

 especially the ones from the second lumbar ganglion. 

 When present, they join the posterior root of the 

 renal plexus often close to the terminations of the 

 lowest splanchnic nerve, and sometimes they end in 

 the posterior renal ganglia. 



intermesenteric nerves. The renal branches from 

 the upper parts of the intermesenteric nerves run 

 almost directly to the renal hilum. The uppermost 

 ones are associated with those arising from the celiac 

 plexus and occasionally from the superior mesenteric 

 ganglion, and those a little lower down are connected 

 with the origins of the superior spermatic nerves. 



Other branches originate from the lower ends of 

 the intermesenteric nerves or from the superior 

 hypogastric plexus (presacral nerve). Except near 

 their terminations they are separate from the other 

 renal nerves; they communicate with the superior 

 and middle spermatic nerves, and are apparently 

 distributed mainly to the renal pelvis and upper 

 ureter. Mitchell suggests that the ureter, renal pelvis, 

 and renal collecting tubules may receive their para- 

 sympathetic supply via these nerves through the 

 caudal (pelvic splanchnic) rather than cranial (vagal) 

 outflow. 



The various renal nerves unite in a plexiform 

 manner around the renal artery. Xo filaments of any 

 size lie anterior to the vein or posterior to the pelvis, 

 and the plexus splits into subsidiary plexuses which 

 accompany the branches of the renal artery into the 

 kidney. A few filaments accompany the superior and 

 inferior renal capsular veins. All nerves of the plexus 

 do not cluster intimately around the renal artery, but 

 several approach only the branches of this vessel in 

 the actual hilum of the kidney. Both preganglionic 

 and postganglionic nerve fibers exist in the renal 

 plexus. The renal nerves and plexus form multiple 

 intercommunications with many other autonomic 

 nerves and plexuses. 



Ganglia of varying size are invariably located in 

 the plexus, and the posterior renal ganglion is the 

 largest and most constant. Many of the ganglia are 

 of microscopic size; these are more numerous in 

 infantile kidney specimens, although not absent in 

 adult kidneys. 



Intrinsic Innervation 



Mitchell (212) has emphasized the difficulties 

 involved in the differential staining of intrinsic nerve 



fibers; reticular fibers are especially troublesome and 

 caution must be exercised in properly separating 

 them from the nerves. Errors of interpretation have 

 resulted from improper identification. The following 

 description is largely from Mitchell and based upon 

 the innervation in man. 



The main renal plexus divides into large bundles 

 which accompany the branches of the renal artery 

 into the kidney, giving off interlobar, arcuate, and 

 interlobular nerves corresponding to the divisions of 

 the artery. They may lie adjacent to the arteries or be 

 imbedded in the adventitia; some spread out in the 

 adventitia and media, but others leave the vessels to 

 run between the tubules. The nerve fibers in the 

 adventitia do not all end in the artery, but may 

 re-emerge into the perivascular space. Definite nerve 

 filaments or endings were not found in the intima of 

 any of the renal vessels, and no fine nerve plexuses 

 were detected around the peritubular capillaries. The 

 fibers are unmyelinated, according to Mitchell. 



nerve supply to cortex. Nerve fibers are much 

 more common in the cortex than in the medulla, and 

 probably more frequent among the convoluted 

 tubules. They are derived from the small bundles of 

 nerve fibers associated with the interlobular arteries. 

 At irregular intervals strands detach themselves from 

 the parent bundles and pass between the tubules 

 where they are connected by occasional anastomoses, 

 and filaments may be traced to the limits of the 

 cortex. 



Many fibers appear to end as free, fine, beaded 

 filaments on the basement membranes or between the 

 tubular cells. Others give off short side branches which 

 end in globular or fusiform swellings. Endings have 

 been seen on the basement membranes and between 

 the cells, but the presence of intracellular endings is 

 doubtful. This aspect has been controversial: some 

 workers believe that nerve fibers may end within the 

 tubular cells (133, 161). 



The glomeruli receive offshoots from the inter- 

 lobular nerves and other filaments which are derived 

 from adjacent interlobular nerve bundles. These 

 offshoots run alongside afferent arterioles, and wind 

 around them in a spiral fashion, supplying these 

 vessels. Knoche (161) has demonstrated a terminal 

 reticulum on the specialized cells of the juxtaglomeru- 

 lar apparatus (polkissen cell). Filaments proceed to 

 the glomerulus, and Mitchell contends that the 

 resultant strands fade away on the capsule or may 

 end in a small series of slight varicosities. Dark 

 staining strands (Romane's stain) have been seen 

 within the glomeruli, but identification as nerves was 



