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# Urine Formation The image depicts the formation of urine in the nephron, which is the functional unit of the kidney. The nephron is responsible for filtering waste products from the blood and producing urine. It consists of two important parts: the renal corpuscle, which filters blood, and the re...

# Urine Formation The image depicts the formation of urine in the nephron, which is the functional unit of the kidney. The nephron is responsible for filtering waste products from the blood and producing urine. It consists of two important parts: the renal corpuscle, which filters blood, and the renal tubule, where the filtered fluid is modified. The image shows the different parts of the nephron and the key processes occurring in each part. Here is a structured breakdown: ## Filtrate Composition - Water (H₂O) - Sodium Chloride (NaCl) - Bicarbonate (HCO₃⁻) - Hydrogen (H⁺) - Urea - Glucose - Amino Acids - Some Drugs ## Countercurrent Exchange - This process of exchange of gradient in vasa recta or peritubular capillaries is called **counter current exchange**. - The blood flow is slower in peritubular capillaries or vasa recta to allow time for passive diffusion. - Helps maintain the concentration gradient inside medulla and making blood more dilute. - Water is secreted then reabsorbed in to the system. Solutes are reabsorbed then secreted in to the medulla. ## Proximal Tubule - Re-absorbs Nutrients, water (H₂O) and sodium chloride (NaCl). - Secretes Hydrogen (H⁺) and bicarbonate (HCO₃⁻). ## Distal Tubule - Reabsorbs Sodium Chloride (NaCl) - Secretes Hydrogen (H⁺) and bicarbonate (HCO₃⁻). - Secretes some drugs and poisons. ## Loop of Henle - The loop of Henle is a U-shaped structure that descends into the medulla and then ascends back up into the cortex. - Important for concentrating the urine. - As the loop descends, water is reabsorbed out of the filtrate and into the medullary interstitium, making the filtrate more concentrated. - As the loop ascends, sodium chloride (NaCl) is reabsorbed from the filtrate, making it less concentrated. ## Collecting Duct - Reabsorbs water (H₂O) and sodium chloride (NaCl). - Secretes Urea ## Urine - The final product of urine is formed and moved into the renal pelvis.