The kidneys are two bean-shaped organs located on either side of your spine, just below the ribcage.
They are part of the urinary system (also called the renal system) and are vital for filtering blood and removing waste from the body.
🧩 Structure of the Kidneys
| Part | Description |
|---|---|
| Cortex | Outer layer where filtration begins |
| Medulla | Inner region containing renal pyramids |
| Renal pyramids | Cone-shaped tissues that collect urine |
| Nephrons | Tiny filtering units (about 1 million per kidney!) |
| Renal pelvis | Funnel-like structure that collects urine |
| Ureter | Tube that carries urine from each kidney to the bladder |
| Renal artery & vein | Bring blood to and from the kidneys |
⚙️ Main Functions of the Kidneys
| Function | Explanation |
|---|---|
| Filtration of blood | Remove waste products, toxins, and extra fluids |
| Urine production | Filtered waste is turned into urine and passed to the bladder |
| Balancing fluids and salts | Maintain proper levels of sodium, potassium, calcium, etc. |
| Blood pressure regulation | Adjust water and salt balance; release renin to control blood pressure |
| Red blood cell production | Produce erythropoietin (EPO) to stimulate red blood cell creation |
| pH balance | Keep your body from becoming too acidic or alkaline |
| Vitamin D activation | Helps convert vitamin D to its active form (for bone health) |
🧪 How Kidneys Work (Step by Step)
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Blood enters the kidney via the renal artery.
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It flows through millions of nephrons.
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Nephrons filter out waste and excess water.
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Clean blood returns to the body via the renal vein.
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Urine (waste + water) flows into the renal pelvis, then the ureter, and down to the bladder.
🩺 Common Kidney Problems
| Condition | Description |
|---|---|
| Kidney stones | Hard mineral crystals that form in the kidney and cause pain |
| Chronic kidney disease (CKD) | Gradual loss of kidney function over time |
| Acute kidney injury | Sudden kidney failure due to infection, injury, or medication |
| Urinary tract infection (UTI) | Bacteria infects the urinary system, sometimes reaching the kidneys |
| Polycystic kidney disease (PKD) | Inherited disorder causing cysts to grow in kidneys |
| Nephritis | Inflammation of the kidneys |
| Kidney failure | When kidneys can’t filter blood properly (may require dialysis or transplant) |
🧠 Fun Facts About the Kidneys
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Each kidney is about the size of a fist and weighs around 150 grams.
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Kidneys filter about 50 gallons (180 liters) of blood every day!
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They produce about 1.5 liters of urine daily.
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You can live a normal life with just one kidney.
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The first successful kidney transplant was performed in 1954.
✅ Quick Summary Table
| Feature | Detail |
|---|---|
| Number | 2 (left and right) |
| Shape | Bean-shaped |
| Location | Lower back, near spine, behind the ribs |
| Main role | Filter blood, remove waste, maintain balance |
| Output | Urine (stored in the bladder) |
| Key hormones | Erythropoietin, Renin, Active Vitamin D (calcitriol) |