Discuss the Process of Urine Formation in Kidney
The kidneys form urine through three main steps: filtration, reabsorption, and secretion. These processes occur in the functional unit of the kidney called the nephron.
1. Glomerular Filtration
- Occurs in the glomerulus, a tuft of capillaries within Bowman’s capsule.
- Blood pressure forces water and solutes (like urea, glucose, salts) through the capillary walls into the capsule.
- Proteins and blood cells are not filtered due to their size.
2. Tubular Reabsorption
- Takes place mainly in the proximal convoluted tubule.
- Essential substances like glucose, amino acids, water, and salts are reabsorbed back into the bloodstream.
- This process is selective and energy-dependent (active and passive transport).
3. Tubular Secretion
- Occurs mainly in the distal convoluted tubule and collecting duct.
- Waste products like hydrogen ions, potassium ions, and drugs are actively secreted into the tubule.
Final Urine Formation
The fluid that remains after reabsorption and secretion is urine. It flows from the collecting ducts into the renal pelvis, ureters, bladder, and finally exits through the urethra.
This process helps the body maintain electrolyte balance, remove waste, and regulate fluid volume and pH.