DISTAL CONVOLUTED TUBULE, CONNECTING TUBULE, AND COLLECTING DUCT

The thick ascending limb, as described in the previous section, courses from the medulla toward the cortex, where it transitions to the distal convoluted tubule. Near this transition point is a specialized group of cells known as the macula densa, which make direct contact with the nephron’s parent glomerulus.

The distal convoluted tubule, like the proximal convoluted tubule, takes a very tortuous course within a small area of the cortex. It transitions to a short connecting segment (or tubule), which in turn leads to the collecting duct.

The collecting duct courses from the cortex toward the medulla adjacent to ducts from neighboring nephrons. In the inner zone of the medulla, these individual ducts join to form larger ducts. By a succession of several such junctions, the papillary ducts are formed, which arrive at the cribriform area of the papillae to drain urine into the minor calyces.