kidney_upper_slim part of part of nephron tubule epithelial cell kidney cortex tubule cell kidney connecting tubule epithelial cell Any nephron tubule epithelial cell that is part of some renal connecting tubule. https://cdn.humanatlas.io/digital-objects/2d-ftu/kidney-nephron/v1.2/assets/2d-ftu-kidney-nephron.png KUPO:0001058 https://cellxgene.cziscience.com/cellguide/CL_1000768 Kidney connecting tubule epithelial cells are found in collecting duct system of the kidney, specifically in at the interconnection segment between the nephron and the collecting ducts. The epithelial cells lining the connecting tubule are crucial for the journey of filtrate before it empties into urine-collecting ducts and therefore play a critical role in maintaining the body’s fluid and electrolyte balance. One of the principal functions of connecting tubule epithelial cells involves the selective reabsorption and secretion of various solutes. This reabsorption process includes critical regulatory electrolytes such as sodium ions (Na+), chloride ions (Cl-), and bicarbonate ions (HCO3-), thus playing a role in the regulation of the acid-base homeostasis. Their function also involves the secretion of potassium ions (K+) into the renal tubular fluid. The connecting tubule epithelial cells are primarily intercalated cells, which can be categorized into two types according to their specific functions: type A intercalated cells, which secrete acid, and the type B intercalated cells, which secrete base (bicarbonate) and reabsorb chloride. By regulating the concentrations of these ions, as well as reabsorption of water, connecting tubule epithelial cells contribute substantively to maintaining the body's electrolyte levels, pH balance, and overall homeostasis. In addition to intercalating cells, the collecting duct system also has principal cells, which are characterized by the expression of the water channel AQP2. AQP2-expressing cells have also been identified in connecting tubules, but there is some controversy whether these represent a unique cell type as there are some morphologic differences compared with principal cells. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) Homo sapiens renal connecting tubule