In the kidney, urine is formed in the nephrons, which are the functional units responsible for filtering blood and producing urine. Here's a step-by-step explanation:
1. Filtration: Blood enters the kidney through the renal artery, and within the nephrons, tiny blood vessels called glomeruli filter out waste products, excess ions, and water from the blood.
2. Reabsorption: After filtration, useful substances like glucose, ions, and water are reabsorbed back into the bloodstream to maintain proper balance in the body.
3. Secretion: Some additional substances like hydrogen ions and potassium ions are actively secreted into the filtrate to further regulate the composition of urine.
4. Concentration: The filtrate that remains after reabsorption and secretion processes undergoes concentration in the collecting ducts, where water is reabsorbed to adjust the final urine concentration.
5. Urine Formation: Finally, the concentrated urine is transported from the collecting ducts to the renal pelvis, through the ureter, and then stored in the bladder until it is eliminated from the body through urination.
By following these steps in the nephrons, the kidney effectively filters the blood, maintains the body's internal environment, and produces urine as a waste product.
