Grade 12 · Biology
Urine formation
Why it matters
Filtration, reabsorption, secretion.
Advanced20m readingPrerequisite: Kidney & nephron structure
How is urine formed in the kidney?
Short answer
Urine forms in the nephron through three steps. Filtration forces water and small solutes from the blood into the nephron at the glomerulus. Reabsorption returns useful substances — glucose, ions, and most water — back to the blood. Secretion adds extra wastes from the blood into the tubule. What remains is urine, carrying wastes out of the body.
🔒
This feature is available in the School Plan.
Upgrade to unlock the full lesson, examples, quiz and practice.
Upgrade PlanRelated topics
Frequently asked questions
- What are the three steps of urine formation?
- Filtration at the glomerulus, reabsorption of useful substances, and secretion of extra wastes into the tubule.
- Why is glucose normally absent from urine?
- It is completely reabsorbed into the blood during reabsorption; glucose in urine can signal a problem such as diabetes.