1. BIO 391- The Excretory System The Structure and Function of the Kidney

2. Function of kidney: Filter blood, reabsorb materials & form urine

3. Cross section of the kidney Over 1 million nephrons in each kidney Nephrons span both the cortex and medulla Renal pelvis: collects urine, passes it to ureter Renal artery: brings blood to kidney Renal vein: transports purified blood back to heart

4. Structure of the nephron

5. Functional Regions

6. Homeostasis by the Kidney Maintain volume of extracellular fluid Maintain ionic balance in extracellular fluid Maintain pH and osmotic concentration of the extracellular fluid. Excrete toxic metabolic by-products such as urea, ammonia, and uric acid.

7. Steps of urine formation Glomerular filtration: o removes solutes from blood o 1 st step in urine formation Tubular reabsorption: o almost all nutrients are reabsorbed by passive or active transport o 2 nd step in urine formation Tubular secretion: o Solutes and waste are secreted into the tubules and collecting duct o Last step in urine formation

8. Production of Urine

9. What is urine made of? 96% water 2% urea 2% other substances e.g.: ammonia, sodium, potassium, chloride, sulphates, phosphates, excess vitamins, drugs Normal urine is acidic, but it depends on diet and other factors