The Role of the Kidneys

• When kidneys fail to work properly, dialysis treatment or a transplant is required
• Kidneys


  • Located in the back of the abdomen
  • Have two important functions: regulate water content in blood, excrete toxic waste products of metabolism
• Blood flow through the kidneys


  1. Blood brought to kidney in renal artery

  2. Renal artery branches off aorta

  3. Kidney regulates/controls water and salt content

  4. Removes urea

  5. Filtered excess water, salts and urea form urine

  6. Urine transported to bladder through ureters

  7. Purified blood returns to circulation through renal vein

  8. Renal vein to heart through vena cava
• Nephrons


  Filtration units of the kidney, also called kidney tubules
• Nephrons start in the cortex of the kidney, loop down into the medulla and back to the cortex
• Nephron regulates the level of water, salts and removes urea from the blood
• Bowman's capsule (renal capsule)


  Surrounds a ball of capillaries close to the capillary knot
• Capillary knot


  High pressure is created by the diameter of the capillary leaving the knot being narrower than the capillary entering
• Ultrafiltration


  1. Water, ions, glucose and other small molecules pass out of the capillary and into the Bowman's capsule

  2. Proteins and blood cells are too big to leave the capillaries to go into the tubule
• Tubule


  Responsible for the selective reabsorption of glucose, some salts, and lots of the water
• Collecting duct


  Responsible for the selective reabsorption of water and for sending urine to the ureter
• Our kidneys regulate the water concentration in our blood and excrete toxic waste
• When kidneys fail to work properly, dialysis treatment or a transplant is required