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The Kidney & Dialysis. Diffusion, osmosis, & active transport in the body. Gross Anatomy. Posterior in the abdominal cavity Bean shaped Just below the rib cage Size of a fist. What do they do?. Kidneys filter waste products and make urine Waste products from cells end up in the blood - PowerPoint PPT Presentation
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The Kidney & Dialysis
Diffusion, osmosis, & active transport in the body
Gross Anatomy
Posterior in the abdominal cavity Bean shaped Just below the rib cage Size of a fist
What do they do?
Kidneys filter waste products and make urine1. 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
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
A closer look
Nephron
The repeating functional unit of the kidney A semi-permeable tube whose job is:
1. Filtration
2. Reabsorption
3. Secretion
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.
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)
Secretion
Opposite of reabsorption Waste (H+ ions, drugs) are pumped from
capillaries directly into the tube
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
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
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
What’s happening in the nephron?
How does structure meet function?
Cells that make up the tube are different depending on their jobs!
Hemodialysis
hemo = blood Internal filters don’t
work, use an external filter
Blood is filtered through an external machine
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)
Is hemodialysis just as good as a kidney?
What do you think?
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
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?
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