Final answer:
The K+ found in urine is secreted by the distal tubule of the nephron.
Step-by-step explanation:
The K+ found in urine is secreted by the distal tubule of the nephron. The distal tubule is responsible for selectively secreting and absorbing different ions to maintain blood pH and electrolyte balance. It plays a crucial role in regulating the final composition of urine. The K+ found in the urine is primarily secreted by the distal tubule, more specifically the distal convoluted tubule (DCT). In the physiology of the nephron, reabsorption and secretion are vital processes for maintaining electrolyte and fluid balance. The distal tubule selectively secretes and reabsorbs various ions, including potassium (K+), to maintain blood pH and electrolyte balance under the influence of hormones like aldosterone. The potassium secreted here eventually makes its way into the urine. The principal cells found in the collecting ducts also play a role in the recovery or loss of sodium and potassium; however, the bulk of K+ secretion that ends up in the urine occurs in the distal tubule.