Renal System肾脏 · 沉默的总调度

Two 150-g filters

Stop 1/6

两个 150 g 的过滤器

The kidneys sit on the back of the waist on both sides — each ~150 g, together only 300 g. That's 0.5% of body weight, yet they receive 20–25% of cardiac output, making them the body's most blood-hungry organ (per unit weight, even more than the brain).

This isn't waste, because the kidney's job isn't 'absorb nutrients' — it's to re-filter all the body's blood. About 1.2 L of blood enters per minute, 125 mL of ultrafiltrate is produced, 99% is reabsorbed, leaving ~1 mL/min of final urine.

The functional unit is the nephron:

Each kidney has ~1 million nephrons, and the number doesn't grow over life (essentially fixed at birth)Each nephron is a glomerulus plus 4 sequential tubular segmentsAfter age 40, you lose ~6000 per year; aging, hypertension, and diabetes all accelerate this
Why do we have two kidneys: after a single kidney transplant, the remaining kidney hypertrophies compensatorily and GFR rises 40–50%, but the reserve is gone — which is why living kidney donors need strict long-term-risk screening. 'Two kidneys' doesn't equal '100% redundancy' — it's more like '~200% reserve + each doing half the work normally', and the reserve value mostly shows in old age.

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本站提供科普与一般性建议，不替代医师诊断或处方；有症状或正在服药请咨询合格医师。 Educational content, not medical advice — consult a clinician for diagnosis or treatment.

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Renal System肾脏 · 沉默的总调度

Two 150-g filters

Stop 1/6

两个 150 g 的过滤器

The kidneys sit on the back of the waist on both sides — each ~150 g, together only 300 g. That's 0.5% of body weight, yet they receive 20–25% of cardiac output, making them the body's most blood-hungry organ (per unit weight, even more than the brain).

This isn't waste, because the kidney's job isn't 'absorb nutrients' — it's to re-filter all the body's blood. About 1.2 L of blood enters per minute, 125 mL of ultrafiltrate is produced, 99% is reabsorbed, leaving ~1 mL/min of final urine.

The functional unit is the nephron:

Each kidney has ~1 million nephrons, and the number doesn't grow over life (essentially fixed at birth)Each nephron is a glomerulus plus 4 sequential tubular segmentsAfter age 40, you lose ~6000 per year; aging, hypertension, and diabetes all accelerate this
Why do we have two kidneys: after a single kidney transplant, the remaining kidney hypertrophies compensatorily and GFR rises 40–50%, but the reserve is gone — which is why living kidney donors need strict long-term-risk screening. 'Two kidneys' doesn't equal '100% redundancy' — it's more like '~200% reserve + each doing half the work normally', and the reserve value mostly shows in old age.

Read story

本站提供科普与一般性建议，不替代医师诊断或处方；有症状或正在服药请咨询合格医师。 Educational content, not medical advice — consult a clinician for diagnosis or treatment.