eis 30: the excretory system
Activity 1: Filtering Blood
In this lesson, you learned all about your kidneys and how important it is that they’re functioning properly. In this activity, you will learn more about the role of your kidney in filtering blood and how kidney function is damaged in kidney disease.
Kidney disease is very common, affecting about 1 in 7 Americans. This is partly because it is caused by other very common diseases, including heart disease, diabetes, and certain autoimmune diseases. It can range in severity from relatively mild, with few to no symptoms (but you could still detect proteinuria—or protein in the urine—on a urine test), to deadly (kidney disease is one of the top ten leading causes of death in America). It typically progresses from mild to severe.
In the severe stages, people with kidney disease need to go on dialysis, which is a medical procedure in which people are hooked up to a machine that cleans their blood for them, through a port similar to an IV in their arm. This takes several hours and can need to happen as frequently as every day, so it can be a huge burden on people’s lives. This video talks more about kidney disease and dialysis:
Kidney disease is very common, affecting about 1 in 7 Americans. This is partly because it is caused by other very common diseases, including heart disease, diabetes, and certain autoimmune diseases. It can range in severity from relatively mild, with few to no symptoms (but you could still detect proteinuria—or protein in the urine—on a urine test), to deadly (kidney disease is one of the top ten leading causes of death in America). It typically progresses from mild to severe.
In the severe stages, people with kidney disease need to go on dialysis, which is a medical procedure in which people are hooked up to a machine that cleans their blood for them, through a port similar to an IV in their arm. This takes several hours and can need to happen as frequently as every day, so it can be a huge burden on people’s lives. This video talks more about kidney disease and dialysis:
A kidney transplant can be curative and completely remove the need for dialysis, but it still requires people to be on immunosuppressants, which can limit the ability to go out in crowded public places, for the rest of their lives. Unfortunately, kidneys are also in short supply. The waiting list for a kidney from a deceased donor (the longest waiting list for any organ transplant) has over 90,000 people on it, meaning that people could wait 5 or even 10 years before getting an organ, which sometimes means they die while waiting for a transplant. Luckily, scientists are working on ways to create new kidneys from scratch through tissue engineering, and some companies say they’re getting pretty close: Some estimate that this could be a reality as soon as the next 5 years.
This activity will give you a chance to see how the structure of the kidney glomerulus—the part of the functional unit (the nephron) that filters all small solutes out of the blood before the rest of the nephron selectively reabsorbs anything good we got rid of in that process and actively secretes anything bad we didn’t get rid of—is important for proper functioning of the kidney, and how the structure of a damaged glomerulus compares to that of a healthy one.
This activity will give you a chance to see how the structure of the kidney glomerulus—the part of the functional unit (the nephron) that filters all small solutes out of the blood before the rest of the nephron selectively reabsorbs anything good we got rid of in that process and actively secretes anything bad we didn’t get rid of—is important for proper functioning of the kidney, and how the structure of a damaged glomerulus compares to that of a healthy one.
materials
- Model of Blood made in EIS 27. If you’d like, you can also add additional food coloring (such as yellow for urea) to this to represent wastes in your blood.
- Coffee filter, cheesecloth, fine mesh sieve, paper towels, or piece of fabric. This represents a healthy glomerulus (a capillary with large fenestrations).
- Colander. This represents a glomerulus that has been damaged.
- Chicken wire or something else of similar mesh size is recommended, but not required. This represents a glomerulus with severe damage.
- Plastic baggie or another watertight container. This represents a glomerulus with scar tissue due to past injury.
- Large bowl to filter into
procedure
1. Filter your blood model through each of the four sizes of mesh indicated in the materials (watertight, small mesh, colander/medium mesh, and, optionally, chicken wire/large mesh). You can either do this by shaking the blood well and filtering only a small amount of the blood through each or by recollecting the blood at the end of each step.
2. Make note of which blood components go through each filter and which do not go through the filter. You may want to remind yourself what each of the components of your model represents in real blood.
3. In a real glomerulus, the force of blood pressure helps to push solutes out of blood quickly. Try adding some pressure to each of the filters (such as by squeezing the filter, especially the plastic baggie and the fine filter). Does this change your observations?
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #GlomerulusEons.
2. Make note of which blood components go through each filter and which do not go through the filter. You may want to remind yourself what each of the components of your model represents in real blood.
3. In a real glomerulus, the force of blood pressure helps to push solutes out of blood quickly. Try adding some pressure to each of the filters (such as by squeezing the filter, especially the plastic baggie and the fine filter). Does this change your observations?
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #GlomerulusEons.
Longitudinal Activity: Making a Model of the Human Body
Add the following to your model of the human body:
- Kidney
- Ureter
- Bladder
- Urethra
Bonus Activity: Dialysis
Note: This activity is not required, as it makes use of materials that are not commonly found in most homes. These materials can be acquired relatively cheaply, and we do think that this activity can be very fun and educational for many students!
As discussed above, dialysis is an important and lifesaving treatment for those with kidney disease, even though there are some significant drawbacks. Dialysis makes use of concentration gradients to clean your blood.
In a dialysis machine, blood is separated from a dialysis fluid using a semipermeable membrane (dialysis tubing). Wastes, salts, glucose, and water from your blood could all hypothetically cross this membrane. Salts and glucose are found in the same concentration in the dialysis fluid as the ideal concentration in your blood, which means that, if you have too little salt and/or glucose, they will move into your blood from the dialysis fluid, and, if you have too much in your blood, they will move from your blood into the dialysis fluid. Wastes are not found in fresh dialysis fluid, so they will move out of your blood and into the dialysis fluid.
This activity will give you the opportunity to explore the functions of dialysis tubing and how this relates to real kidney function. It’s fairy open-ended as the main goal is for you to explore using solutes and solvents that you already have on hand.
As discussed above, dialysis is an important and lifesaving treatment for those with kidney disease, even though there are some significant drawbacks. Dialysis makes use of concentration gradients to clean your blood.
In a dialysis machine, blood is separated from a dialysis fluid using a semipermeable membrane (dialysis tubing). Wastes, salts, glucose, and water from your blood could all hypothetically cross this membrane. Salts and glucose are found in the same concentration in the dialysis fluid as the ideal concentration in your blood, which means that, if you have too little salt and/or glucose, they will move into your blood from the dialysis fluid, and, if you have too much in your blood, they will move from your blood into the dialysis fluid. Wastes are not found in fresh dialysis fluid, so they will move out of your blood and into the dialysis fluid.
This activity will give you the opportunity to explore the functions of dialysis tubing and how this relates to real kidney function. It’s fairy open-ended as the main goal is for you to explore using solutes and solvents that you already have on hand.
materials
- Dialysis tubing. This can be acquired relatively inexpensively ($10-20 for 10 feet of tubing) through Amazon or other online retailers or through lab or medical supply shops. (Note that you do not need it to be sterilized or medical-grade, which are much more expensive.)
- Rubber bands, ties, or tubing clamps. This is used to seal off the ends of your tubing.
- Scissors,
- Solutions of water and various concentrations of solute. This is where the project becomes flexible: The main goal is for you to explore a bunch of possibilities to see what crosses your barrier, what doesn’t, and what direction solutes move in. We strongly recommend using supplies that are already easily available in your home, such as salt, sugar, and/or food coloring. If you’re not squeamish, you can even use real urine! (Don’t worry, it’s sterile, as long as you don’t have a urinary tract infection).
- You may find a funnel or syringe to be helpful in filling the dialysis tubing, but this is not absolutely necessary.
- Containers such as bowls or glasses.
procedure
1. Dialysis tubing doesn’t really look much like a tube when it comes packaged, because the membrane is very thin and it’s usually packed flat. To use the tubing in your experiments:
2. Put the dialysis tubing in a second liquid of your choosing. Again, it’s best to choose your liquids so that you’re establishing a concentration gradient and can see how things move.
3.Repeat steps 1 and 2 for as many experimental groups as you’d like.
4. Leave the dialysis tubing for several hours to a few days and note your observations.
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #DialysisEons.
- Cut off about 6 inches of tubing from the roll using a pair of scissors.
- Get the tubing wet, by submerging it in water or another fluid. You should notice that it becomes very fluid and kind of slippery.
- Tie off or clamp one end of the dialysis tubing with the rubber bands, ties, or tubing clamps. This should be a watertight seal.
- Pinching the flat side of your tubing near the opening, rub your fingers back and forth. You should notice that the two membranes start to come apart.
- You can now fill the dialysis tubing with a liquid of your choosing. Remember, the goal is for you to explore how solutes and water move by diffusion and osmosis, so it’s best to establish a concentration gradient. A funnel or syringe may help you to fill it.
- Tie off or clamp the other end of your tube.
- This video gives a helpful overview of how to set up dialysis tubing. Your liquids don’t have to be exactly the same as theirs.
2. Put the dialysis tubing in a second liquid of your choosing. Again, it’s best to choose your liquids so that you’re establishing a concentration gradient and can see how things move.
3.Repeat steps 1 and 2 for as many experimental groups as you’d like.
4. Leave the dialysis tubing for several hours to a few days and note your observations.
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #DialysisEons.
Bonus Challenge: Tissue Engineering
Note: This activity is not required, but it can be a fun challenge for students who want to put their creative thinking and engineering skills to the test!
Tissue engineering is a fascinating field of research, and it’s a bit of a hot-topic in science right now. The basic idea is to recreate a functional human organ using biomaterials and cells. There are a couple of different avenues of research being pursued in this field, some of which have been around for a while but haven’t quite overcome some of the biggest challenges in making fully functional tissue and some of which are newer but very promising. It has far-reaching implications, ranging from eliminating the need for organ waitlists to improving the ways we do research. Here’s a few videos, if you’d like to explore this topic further (featuring a quick cameo from yours truly in the last video):
Tissue engineering is a fascinating field of research, and it’s a bit of a hot-topic in science right now. The basic idea is to recreate a functional human organ using biomaterials and cells. There are a couple of different avenues of research being pursued in this field, some of which have been around for a while but haven’t quite overcome some of the biggest challenges in making fully functional tissue and some of which are newer but very promising. It has far-reaching implications, ranging from eliminating the need for organ waitlists to improving the ways we do research. Here’s a few videos, if you’d like to explore this topic further (featuring a quick cameo from yours truly in the last video):
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Kidneys are an especially hot-topic in the field of tissue engineering because of the unique challenges associated with printing something as tiny, complicated, and important as a nephron, with all of its microvasculature.
This activity will challenge you to think like a tissue engineer to recreate a structure that functions in the same way as a nephron. This video walks through each of the parts of the nephron and what they do, if you’d like more background:
This activity will challenge you to think like a tissue engineer to recreate a structure that functions in the same way as a nephron. This video walks through each of the parts of the nephron and what they do, if you’d like more background:
materials
You choose! You will need something that functions in a similar way to the glomerulus and tubules of the kidney, at a minimum. We encourage you to be mindful of your resources and use primarily those materials that you might already have on hand.
procedure
Create a “nephron” of your own design that has functions similar to the glomerulus and tubules of the kidney. We encourage you to think about how each of these things works and what materials you might have that have a similar function.
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #TissueEngineeringEons.
If you’re having fun or learning something cool, we want to see it! If you have an Instagram and the permission of your relevant responsible adult, share with us @eons_learning, #TissueEngineeringEons.