Welcome to GattPrep!
Imagine your home without a trash bin or bathroom. Gross, right? 😬 That’s exactly what your body would be like without the excretory system—a vital group of organs that remove waste products from your blood and body.
Your cells produce waste all the time—from breathing, eating, and simply being alive. The excretory system keeps your internal environment clean and balanced. In this lesson, you’ll learn which organs are involved, how they work, and how to keep this essential system healthy.
The excretory system removes metabolic waste from the body. These are waste substances produced during chemical reactions in cells (like respiration).
Excretion ≠ Egestion
🔹 Excretion is the removal of waste produced by cells (e.g., urea, carbon dioxide).
🔹 Egestion is the removal of undigested food (via the anus, not part of excretion).
| Organ | Waste Removed | Function |
|---|---|---|
| Lungs | Carbon dioxide, water vapor | Remove waste gases during exhalation |
| Skin | Sweat (water, salt, urea) | Cools the body and removes waste through sweat glands |
| Liver | Urea (via blood to kidneys) | Converts harmful substances (like ammonia) into urea |
| Kidneys | Urea, water, salts | Filter blood to form urine |
| Bladder | Urine | Stores urine before release |
| Structure | Function |
|---|---|
| Kidneys | Filter blood, remove waste (urea), control water/salt balance |
| Ureters | Carry urine from kidneys to bladder |
| Bladder | Stores urine |
| Urethra | Passes urine out of the body |
🖼️ [Insert diagram of urinary system here]
Inside each kidney are about 1 million nephrons—tiny filters.
Here’s how they work:
Blood enters the nephron.
Waste (urea), excess salts, and water are filtered out.
Useful substances like glucose are reabsorbed into the blood.
Waste becomes urine, which is sent to the bladder.
Too much water = dilute urine (light yellow)
Too little water = concentrated urine (dark yellow)
💡 Your kidneys maintain homeostasis—keeping a stable internal environment.
| Condition | Description | Symptoms | Prevention/Treatment |
|---|---|---|---|
| Bedwetting | Involuntary urination at night | Urine leaks during sleep | Behavior training, medication |
| Kidney Stones | Hard crystals from salts | Pain, blood in urine | Drink water, avoid too much salt |
| Urine Retention | Inability to fully empty bladder | Discomfort, frequent urge | Medical attention |
| Urinary Tract Infection (UTI) | Bacterial infection | Burning sensation, frequent urination | Good hygiene, antibiotics |
| Prostate Problems (in males) | Enlarged gland affects urination | Difficulty urinating | Medical check-ups |
🧠 Problem: Kwabena has been sweating a lot and is also urinating less. Why is this happening?
✅ Step-by-Step Solution:
Sweating causes water loss through the skin.
To prevent dehydration, kidneys conserve water.
Less water in kidneys = less urine.
✔️ Answer: His kidneys are conserving water because he is losing a lot through sweating.
(a) The functional unit of the kidney is the __________.
(b) The organ that removes carbon dioxide is the __________.
Answers:
(a) nephron
(b) lungs
| Organ | Waste Removed |
|---|---|
| (i) Liver | A. Sweat |
| (ii) Kidneys | B. Carbon dioxide |
| (iii) Skin | C. Urea |
| (iv) Lungs | D. Urine |
Answers:
(i) → C
(ii) → D
(iii) → A
(iv) → B
Q: Why is excretion important to your health?
A: It removes harmful substances like urea and helps maintain a clean and balanced internal environment.
Here’s what we’ve learned today:
The excretory system removes metabolic waste from the body.
Main organs include the kidneys, lungs, liver, skin, and bladder.
The kidneys filter blood and produce urine.
The nephron is the functional unit of the kidney.
Disorders include kidney stones, UTIs, and bedwetting.
Think about what would happen if your kidneys stopped working.
How would your body be affected? What support might a person need?
Write your thoughts in your journal or discuss with a classmate.
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