urine formation

• The color of your urine can vary depending on what you eat, any medications you are taking, and how much water you drink
• Dark yellowish urine


  Indicates a high amount of solute inside your body
• Colorless urine


  Indicates a low amount of solute inside your body
• Reddish or bluish urine


  Indicates the presence of certain substances in the urine
• Processes involved in urine formation

  • Filtration
  • Reabsorption
  • Secretion
  • Excretion

  
• Processes in the Distal Tubule


  1. Na+ and Cl- are reabsorbed

  2. Principal cells reabsorb Na+ and water, secrete K+

  3. Intercalated cells reabsorb K+, secrete H+
• The urine formed has an osmolarity of 1,200 mOsm/L, 4 times more concentrated than blood
• Kidneys filter 1,600 L of blood daily, 180 L of filtrate is processed, 99% is reabsorbed, 1.5 L of urine is excreted

  
• Vertebrate kidney


  • One of the most efficient excretory organs in the animal kingdom
  • Structure is key to its function
• Glomerulus is porous and permeable to small solutes and water
• Proximal tubule reabsorbs valuable ions, salts, and water
• Descending limb of loop of Henle reabsorbs water through aquaporins
• Ascending limb of loop of Henle is impermeable to water, NaCl is transported out
• Distal tubule and collecting duct regulate reabsorption and secretion of ions