Connecting tubule

In the kidney, the collecting tubule (CNT, or junctional tubule, or arcuate renal tubule) is a tubular segment of the renal collecting duct system that connects the distal convoluted tubule to the cortical collecting duct.

Classification
Many sources include the connecting tubule as part of the collecting duct system. However, the embryological origin is more similar to the nephron than it is to the rest of the collecting duct (which derives from the ureteric bud), and other sources therefore classify the connecting tubule with the nephron.

Naming
Some connecting tubules, usually associated with juxtamedullary nephrons, arch upwards before reaching the cortical collecting ducts. It is this "arcuate" feature which gives the tubule its alternate name.

Function
It participates in the regulation of water and electrolytes, including sodium, and chloride.

The CNT is sensitive to both isoprotenerol (more so than the cortical collecting ducts) and antidiuretic hormone (less so than the cortical collecting ducts), the latter largely determining its function in water reabsorption.