Notes on Kidney Function and Structure • Kidney Basics: • Weight: ~0.5 kg. • Shape: Fist-shaped. • Function: Filter wastes from blood; hold up to 25% of the body’s blood at a time. • Urine Formation and Storage: • Filtration: Kidneys filter waste, conducting it to the bladder via ureters. • Storage: • Urinary sphincter muscle: Acts as a valve at the bladder’s base, allowing urine storage. • Urge Signals: • At ~200 mL: Bladder stretches slightly; nerves signal the brain. • At ~400 mL: Stretch receptors activate further; urgency increases. • At ~600 mL: Voluntary control is lost; sphincter relaxes, urine enters the urethra and is voided. • Kidney Anatomy (Referencing Figure 1): • Cortex: Outer layer of connective tissue encircling the kidney. • Medulla: Inner layer beneath the cortex. • Renal pelvis: Hollow chamber connecting the kidney to the ureter.