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Human Body Study

Nephron

The kidney’s microscopic filtering unit — each kidney holds about a million of them.

The urinary tract Two kidneys at top with ureters descending to a single bladder and urethra exiting below; a separate inset shows a nephron, the kidney's microscopic functional unit. Each label links to the article for that part. Nephron Kidneys Ureters Bladder Urethra The urinary tract — kidneys, ureters, bladder, urethra; the nephron is the kidney's microscopic functional unit.

Structure

Section titled “Structure”
  • A glomerulus — a tuft of capillaries that filters fluid out of the blood.
  • A long tubule — where most of that filtered fluid is reclaimed.

What it does

Section titled “What it does”
  1. Filters a large volume of fluid out of the blood.
  2. Reabsorbs almost all of it — water, glucose, salts — back into the blood.
  3. Secretes additional wastes into what remains.
  4. What is left becomes urine.

Key idea

Section titled “Key idea”

The nephron filters nearly everything and then takes back what the body needs — a wasteful-looking strategy that allows extremely precise control.