Collecting duct system

A manifold (lat. renal tubule colli gens ) is a fine tube into the kidney for drainage of urine from the nephrons. The collecting ducts extend from the renal cortex (cortex renis ) through the renal medulla (medulla renis ) and open into the Nierenpapillengang ( papillary duct ) and this in turn over a renal calyx into the renal pelvis. Developmentally, arise the headers from the ureteric bud.

The epithelial cells of the collecting ducts contain few organelles, which is why they appear bright in routine histological preparation. The cell boundaries are clearly the epithelium and the number of cell layers decreases with increasing size of the tubes. The epithelium is normally not permeable ( permeable ) for water. The antidiuretic hormone ( vasopressin ) ensures that this permeability is increased by the incorporation of aquaporins ( AQP2 ) in the plasma membrane, thereby H2O enters the hypertonic renal medulla. The urine becomes more concentrated. Here is a passive transport ( osmosis) instead due to the concentration gradient of H2O from the tubule to the renal medulla.

• Anatomy of the kidney
• Histology of the urinary organs