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macula densa

[dĕn′sə]
n.
  1. A densely packed group of modified epithelial cells in the distal tubule of a nephron, adjacent to the juxtaglomerular cells.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.