1. Your Kidneys and Diffusion

2. What are your kidneys?
The kidneys are bean-shaped organs, each about the size of a fist. They are located near the middle of the back, just below the rib cage, one on each side of the spine.

3. What do my kidneys do?
The kidneys are sophisticated reprocessing machines. Every day, a person’s kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water. The wastes and extra water become urine, which flows to the bladder through tubes called ureters. The bladder stores urine until releasing it through urination. Wastes in the blood come from the normal breakdown of active tissues, such as muscles, and from food. The body uses food for energy and self-repairs. After the body has taken what it needs from food, wastes are sent to the blood. If the kidneys did not remove them, these wastes would build up in the blood and damage the body.

4. How does waste exit the kidneys and enter the blood?
Through diffusion!!!
Solutes move an area of high concentration within special cells of your kidneys to an area of low concentration in your bloodstream. Solutes that the body can reuse, like glucose, vitamins, and minerals remain in the clean blood, while waste is removed. This waste (urine) is then sent through the ureters, to the bladder for removal from your body.

5. What if my kidneys don’t work any more?
If a person’s kidneys stop working completely, the body fills with extra water and waste products. This condition is called uremia. Hands or feet may swell. A person will feel tired and weak because the body needs clean blood to function properly.
Untreated uremia may lead to seizures or coma and will ultimately result in death. A person whose kidneys stop working completely will need to undergo dialysis or kidney transplantation.

6. What is Dialysis?
Dialysis uses a special filter called a dialyzer that functions as an artificial kidney to clean a person’s blood. The dialyzer is a canister connected to the dialysis machine. During treatment, the blood travels through tubes into the dialyzer, which filters out wastes, extra salt, and extra water. Just like in your kidneys, this process is accomplished through diffusion!
Then the cleaned blood flows through another set of tubes back into the body. The dialysis machine monitors blood flow and removes wastes from the dialyzer. Dialysis is usually performed at a dialysis center three times per week for 3 to 4 hours.

7. How does Diffusion occur in a Dialysis Machine?
Using what’s called Dialysis Tubing!!!
Dialysis tubing is a small tube inserted into a person's body to help with blood circulation. Dialysis tubing is a semi- permeable membrane, and is useful in helping with diffusion through the body. Useful liquids and molecules are allowed through, while larger, harmful molecules are blocked out. The main purpose of dialysis tubing is to help a patient with kidney failure. The tubing is hooked up to a machine that artificially cleans out a person's body like a kidney. The tubes do this through a process of diffusion, filtering the toxins out of the body just like a kidney would.

8. What is dialysis tubing made from?
Dialysis Tubing is a type of semi- permeable membrane tubing made from regenerated cellulose or cellophane. When placed in liquid, the walls of the tubing separate, allowing the liquids, such as blood or water, to pass through, and wastes to diffuse out.

9. How are we going to use dialysis tubing in lab?
We will soak the dialysis tubing in distilled water to loosen it up.
Next, we will tie off one end of the dialysis tubing and fill it with a “mystery solution”. Your mystery solution may contains, sugar, proteins, salt, etc.
Then we will tie off the other end, to make it look like a tootsie roll.
Lastly, we will place it in a beaker of distilled water, and let it sit over night.

10. Exit Ticket: What is the semi-permeable Dialysis Tubing representing in this experiment? Using the word diffusion or diffuse, predict what will happen to the “mystery solution” inside the tubing.