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Urine formation
The kidneys produce urine through three main processes: 1) Filtration of water and dissolved substances from the blood in the glomeruli into the Bowman's capsule. 2) Reabsorption of water, nutrients like glucose, and ions like sodium out of the kidney tubules and back into the bloodstream, preventing their loss in urine. 3) Secretion of substances like hydrogen and potassium ions, ammonia, and drugs from the blood into the kidney tubules to be eliminated in urine, which helps regulate acid-base balance.
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Urine formation
- 3. For the productionof urine, the kidneys do not simply pick waste products out of the bloodstream and send them along for final disposal.
- 4. The kidneys' 2million or more nephrons (about a million in each kidney) form urine by three precisely regulated processes
- 5. 1) FILTRATION 2) REABSORPTION 3)SECRETION
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- 7. FILTRATION • Blood coursesthrough the GLOMERULI, much of its fluid, containing both useful chemicals and dissolved waste materials, soaks out of the blood through the membranes (OSMOSIS & DIFFUSION) • It is then filtered and then flows into the BOWMAN'S CAPSULE • The product formed is collectively known as GLOMERULAR FILTRATE
- 8. FILTRATION GLOMERULAR FILTRATE • water,waste products, excess salts (Na+ & K+), glucose, and other chemicals that have been filtered out of the blood
- 10. FILTRATION GLOMERULAR FILTRATION RATE •Totalrate of filtration of the glomerulus •The normal rate is 125mL/min 125mL/min 7500mL/hr 180L/day
- 11. FILTRATION But why don’twe excrete 180L of water per day?
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- 13. REABSORPTION •movement of substancesOUT OF THE RENAL TUBULES back into the BLOOD CAPILLARIES located around the tubules • Substances reabsorbed are water, glucose and other nutrients, and sodium (Na+) and other ions
- 14. REABSORPTION •Reabsorption begins in the proximal convolutedtubules and continues in the loop of Henle, distal convoluted tubules, and collecting tubules.
- 15. REABSORPTION •about 99% ofthe 180L of water that leave the blood each day by glomerular filtration returns to the blood from the proximal tubule through the process of PASSIVE REABSORPTION.
- 16. REABSORPTION • nutrient glucoseis entirely reabsorbed back into the blood from the proximal tubules. In fact, it is actively transported out of the tubules and into the PERITUBULAR CAPILLARY BLOOD • Sodium ions (Na+) and other ions are only partially reabsorbed from the renal tubules back into the blood.
- 17. REABSORPTION • Amount dependslargely on how much salt we take in from the foods that we eat. ↑Na+ intake = ↓Na+ reabsorption in the blood
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- 20. SECRETION •substances move intothe distal and collecting tubules from blood in the capillaries around these tubules
- 21. SECRETION secretion is reabsorption inreverse • REABSORPTION - substance from tubules blood • SECRETION - substance from blood tubules
- 23. SECRETION •Substances are secretedthrough either an ACTIVE TRANSPORT MECHANISM or as a result of DIFFUSION across the membrane • Secretion plays a crucial role in maintaining the body's ACID-BASE BALANCE, another example of an important body function that the kidney participates in.
- 24. SUMMARY •Filtration of waterand dissolved substances out of the blood in the glomeruli and into Bowman's capsule;
- 25. SUMMARY •Reabsorption of waterand dissolved substances out of the kidney tubules back into the blood (note that this process prevents substances needed by the body from being lost in the urine);
- 26. SUMMARY •Secretion of hydrogenions (H+), potassium ions (K+), ammonia (NH3), and certain drugs out of the blood and into the kidney tubules, where they are eventually eliminated in the urine.
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