— A Journey Through the Excretory System —
Welcome, scientist. Before we begin, please identify yourself.
Estimated time: 35 minutes. Read each section carefully and answer all questions.
Read carefully. The vocabulary you learn here will be the foundation of every other section in this lab.
Your body is constantly working to keep you alive—and one of its most important jobs is taking out the trash. The excretory system is your body's waste-removal team, and the kidneys are its star players.
You have two kidneys, each about the size of your fist, sitting just below your rib cage. Every minute, they filter about a quarter cup of your blood. By the end of the day, your kidneys have cleaned every drop of blood in your body around 40 times.
Inside each kidney are about one million tiny filters called nephrons. Blood enters a nephron through a tangled ball of capillaries called the glomerulus. Pressure pushes water and small molecules out of the blood—including waste like urea, which forms when your body breaks down protein. This step is called filtration.
But your body doesn't want to lose everything useful. As the filtered fluid moves through the nephron's tubule, glucose, salts, and most of the water are pulled back into the blood. This rescue step is called reabsorption. Whatever is left over becomes urine.
From the kidneys, urine flows down two tubes called ureters into the bladder, which stretches to hold about two cups of liquid. When you go to the bathroom, urine exits the body through the urethra.
This entire system helps your body maintain homeostasis—a stable internal environment. Without your kidneys filtering blood and balancing water, your body chemistry would fall apart in a matter of days.
Unscramble each set of letters to reveal a vocabulary word. Use the hint if you get stuck.
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The kidneys are bean-shaped organs that work all day to clean your blood. Each one contains about a million tiny filters called nephrons. Blood first enters a small ball of capillaries known as the glomerulus, where pressure forces water and waste out in a process called filtration.
As the fluid travels through the tubule, useful materials are pulled back into the blood. This rescue step is called reabsorption. The waste that remains—mostly water and a chemical called urea—is now urine. The urine flows down a tube called the ureter to the bladder, which stores it until you visit the bathroom. It then leaves the body through the urethra. This entire process keeps the body in homeostasis.
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Complete each sentence with at least one full thought. Use what you learned from the reading.
In this lab simulation, you control how much water a person drinks. Watch how the nephron's output changes — and answer the questions below.
Background: A nephron has three jobs. (1) The glomerulus filters blood under pressure. (2) The tubule reabsorbs useful substances like glucose, salts, and water back into the blood. (3) Whatever isn't reabsorbed becomes urine.
What changes with hydration? When you drink a lot of water, the nephron reabsorbs less water — so urine becomes more dilute (lighter color, larger volume). When you're dehydrated, the nephron reabsorbs as much water as possible — so urine becomes concentrated (darker, smaller volume).
Directions: Move the slider to set the patient's water intake. Click "Send Blood Drop" to release a drop into the glomerulus. Observe what happens, then read the output. Run the simulation at least three different intake levels before answering the questions.
Read the patient case carefully. Use what you've learned to answer the diagnostic questions.
A research team measured urine output for 5 people who drank different amounts of water in one day. Study the data, then answer the questions.
| Patient | Water Intake (oz) | Urine Output (mL) | Urine Color |
|---|---|---|---|
| A | 8 | 200 | Dark yellow |
| B | 16 | 400 | Yellow |
| C | 32 | 800 | Pale yellow |
| D | 48 | 1100 | Nearly clear |
| E | 64 | 1400 | Clear |
Make sure you've answered every question. Click below when you're done.
A "✓" means full credit; "~" means partial credit (open response with substantial answer).