1466 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



course of the vasa recta (251). They begin blindly 

 in two locations: closely adjacent to the capsules of 

 cortical glomeruli and beneath the mucosa of the 

 papilla (fig. 12). The cortical lymphatic capillary 

 networks do not have a functional relationship to 

 the glomeruli. There is apparently no entry (248). 



The lymphatics from the cortex with an inter- 

 lobular course drain toward the arcuate vessels. 

 Those from the medulla, draining the vasa recta, join 

 the cortical branches at the arcuate level, then pass 

 out with the interlobar vessels toward the renal pelvis. 

 After converging at the hilum of the kidney, they 

 course as perivascular channels to the cysterna chyli 

 and thoracic duct (230, 261). Valves appear to be 

 lacking in the lymphatics of the renal parenchyma 

 but are present in the large trunks of the renal sinus. 



Figures for the volume of lymph produced by the 



fig. 12. The black threadlike lines indicate the greater and 

 lesser lymphatic systems of the human kidney. The arrows show 

 the probable direction oflymph flow;a: capsule; b: interlobular 

 vein; c: interlobular artery; d: glomerulus; e: arcuate artery;/: 

 arcuate vein, »: interlobar artery; h: interlobar vein; i: papilla. 

 [After Rawson (251).] 



kidney are scarce. Single capsular lymphatics of the 

 dog yield flows of ca. 1 ml per hour (176, 177, 304). 

 An estimate from the data of Schmidt & Hayman 

 (266) yields a total of ca. 7 ml per hour per kidney. 



Available anatomical evidence indicates that the 

 capsular lymphatics join with the cortical and medul- 

 lary lymphatics. Lymph flow increases when the 

 kidney is subjected to osmotic diuretics (106, 230, 

 266). It is enhanced by ureteral obstruction. Pyelolym- 

 phatic backflow is evidenced by the fact that dye has 

 been shown to move from the pelvis into the lymphat- 

 ics with increased intrapelvic pressure. Elevation of 

 renal venous pressure in the dog by 1 4 to 35 cm results 

 in approximately 3-fold to 5-fold increase in lymph 

 flow (123, 177). Marked increase in lymphatic pres- 

 sure accompanies venous obstruction (157). Elevation 

 of arterial pressure does not markedly increase lymph 

 flow from hilar vessels: 0.023 ml per min at 58 mm 

 Hg to 0.039 m l P er mm at '57 mrn Hg (124). 



It is of considerable interest that the lymph is high 

 in sodium, chloride, and urea content compared to 

 plasma and thoracic duct lymph (176, 304). LeBrie 

 & Mayerson (176) have found Na and CI concentra- 

 tions of 162 and 140 per liter, respectively, compared 

 to 145.7 anc ' 1 10.5 in the plasma, and 145.6 and 1 2 1 .3 

 in the thoracic duct lymph. Interestingly, the K 

 content does not differ significantly. These findings 

 support the countercurrent hypothesis, for it is to be 

 expected that these concentrations will be elevated 

 as a result of the contribution of the medullary 

 lymphatics which drain the papillary zone of hyper- 

 osmolarity of the kidney. K. is not a significant con- 

 tributor to this hyperosmolarity (267). This is further 

 supported by the low glucose content of this fluid 

 relative to plasma (304), suggesting an important 

 source beyond the proximal convoluted tubules. 

 An interesting avenue of investigation of the counter- 

 current mechanism thus appears to be afforded by a 

 study of the renal lymphatics. 



The renal lvmph protein concentration averages 

 2.9 g per 100 ml as compared to 5.83 g per 100 ml for 

 the plasma proteins (177). Evidently the renal lym- 

 phatics subserve an important function for operation 

 of the countercurrent system by draining off excessive 

 protein filtered by the vasa recta, which might other- 

 wise accumulate in the interstitial spaces of the me- 

 dulla. Removal of such protein would act to maintain a 

 more favorable gradient of movement of interstitial 

 fluid into the vasa recta, attracted by the relatively 

 higher oncotic pressure. 



