Collecting Tubules

The DCT ends in the collecting duct system which carries the urine through the medulla to the end of the papilla. Collecting tubules are regularly shaped in cross section as compared with the often irregularly shaped sections of the nephron. The lining epithelium of the collecting system gradually increases in height from a simple cuboidal epithelium in the arched tubules to a tall columnar epithelium in the papillary ducts (see R-P or R-K-P, Pl. 79). Look carefully at the epithelium lining the renal calyx at the apex of the medullary pyramid and identify collecting ducts. Collecting ducts have large, more regular, diameters, and are comprised of uniform, lightly stained columnar epithelial cells (B-67, H&E [2.5x-labeled, 10x, 20x-labeled, 40x]; B-71, H&E [2.5x, 10x, 20x, 40x]. Basement membranes are unusually important structures for the functioning of the kidney. Since a principal constituent of the basement membrane is polysaccharide, this structure stains well with the PAS stain. Study a PAS-stained section of kidney (B-66, B- 68, B-69) and carefully note where the prominent basement membranes are found. The stain also shows the brush border of the proximal convoluted tubules and may selectively demonstrate granules in the juxtaglomerular cells of afferent arterioles (B-66 [20x, 40x]).

Collecting Tubule Identifications

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-- AshleyLPistorio - 23 May 2007