1. The Kidney & Dialysis Diffusion, osmosis, & active transport in the body

2. Gross Anatomy Posterior in the abdominal cavity Bean shaped Just below the rib cage Size of a fist

3. What do they do? Kidneys filter waste products and make urine 1. Waste products from cells end up in the blood 2. Blood circulates around the body including the kidneys – Artery = away from the heart, into the kidney – Capillaries = thin walls allow waste to leave – Vein = leaves the kidney, back to the heart

5. Kidney Facts The rate of filtration is approximately 125 ml/min or 45 gallons (180 liters) each day. Considering that you have 7 to 8 liters of blood in your body, this means that your entire blood volume gets filtered approximately 20 to 25 times each day! www.how.stuffworks.com

6. A closer look

7. Nephron The repeating functional unit of the kidney A semi-permeable tube whose job is: 1. Filtration 2. Reabsorption 3. Secretion

8. Filtration Plasma (containing water, salts, food, waste, and other solutes) pass from the blood into the nephron. Blood cells cannot fit through the membrane filter and remain in the capillary.

9. Reabsorption Both active and passive transport move good molecules from the nephron tube back into the blood stream Solutes are pumped (actively transported) back into the capillaries Water follows  osmosis Bad stuff like waste is left in the tube headed to the bladder Anything that doesn’t get reabsorbed into the blood gets “peed” out (becomes urine)

10. Secretion Opposite of reabsorption Waste (H+ ions, drugs) are pumped from capillaries directly into the tube

11. What if it doesn’t work? Kidney usage is usually measured in percent If you lose a kidney you can still filter 100% (you really only need one) When total kidney function drops below 20% it can be lethal Treatment- dialysis

12. The dialysis A dialysis tube acts as the nephron Blood is pumped through the dialysis tube into a machine The dialysis tube passes through a solution allowing diffusion and osmosis to remove waste and excess water

13. Why does it work? A waste product like urea is more concentrated in the blood than in the fluid (dialysate) so the urea passes through and is washed away

14. What’s happening in the nephron?

15. How does structure meet function? Cells that make up the tube are different depending on their jobs!

16. Hemodialysis hemo = blood Internal filters don’t work, use an external filter Blood is filtered through an external machine

17. Life on dialysis Kidneys work 24/7 to get the job done Dialysis is periodic, not continuous Dialysis takes 4-5 hours Why can’t all the blood be filtered at once? Patients go to a clinic 3 times a week (MWF or THS)

18. Is hemodialysis just as good as a kidney? What do you think?

19. Hemodialysis Effectiveness About 10% as effective as normal kidneys Became available in the early 60s Some of the first patients are still alive Not a full life expectancy Without dialysis- certain death 20 million Americans

20. Be the doctor! Manipulating the dialysate In end-stage renal (kidney) failure potassium concentrations get really high This can cause big problems (Na+/K+ pump) What should you do to the concentration of potassium ions in the dialysate to fix this problem?