Waste Removal & the Human Urinary System

1. Waste Removal & the Human Urinary System Sections 3.7 – 3.8 Bio 391 http://www.youtube.com/watch?v=glu0dzK4dbU

2. Waste Removal • Removing wastes is essential to homeostasis. • Organisms in water … • Don’t worry about drying out • Must worry about excreting excess water • Ex: Paramecium’s contractile vacuole • Some removal mechanisms • Simple Organisms • Excretes all wastes through external surface • Hydra, sponges • More complex organisms (ie. Fish) • CO2 – removed through gills • Salt is removed through gills in salt water fish

3. Metabolic Nitrogenous Wastes • Created from the digestion of proteins • Amino acids Amino groups  ammonia • Ammonia is very TOXIC to cells • Methods of Removal: • Immediate, direct ammonia release • More simple aquatic organisms • water “flushes” it out • Convert ammonia to urea • Less toxic, can be stored for a while • Allows for conservation of water • Humans, mammals, some fish, amphibians • Convert to uric Acid • Released as crystal form, “pastey” • Conserves even more water • Birds & desert reptiles

4. Metabolic N-Wastes Ammonia >>> urea >>> uric acid Most toxic Least toxic Requires most water Requires least water • Evolution of different methods… • Related to water availability and whether or not ammonia can be diluted • Further adaptations aid in conserving water

6. Human Urinary System • Kidneys • Nephrons • Excretory tubules in humans • Processes blood, filtering out N-wastes • Regulates water balance – adjusts salt concentration in blood • Lungs • Skin

7. Nitrogenous Waste Digestion: Protein to amino groups Amino acids turned into ammonia and converted to urea in the liver Urea enters circulation (blood) Urea is concentrated by the kidneys Removed as urine

8. The Urinary System • 2 Kidneys • 2 ureters • 1 bladder • 1 urethra Nephron= “functional unit”

9. Urinary System Blood into kidney via renal arteryBlood filtered in nephron (waste=urine)Urine leaves kidney via ureterUrine stored in urinary bladderDrains out urethra

12. Components of The Nephron • Glomerulus: mechanically filters blood • Bowman's Capsule: mechanically filters blood • Proximal Convoluted Tubule: Reabsorbs 75% of the water, salts, glucose, and amino acids • Loop of Henle: Countercurrent exchange, which maintains the concentration gradient • NaCl moves by active transport and diffusion • Distal Convoluted Tubule: Tubular secretion of H+ ions, potassium, and certain drugs. • Collecting Duct: Collects all wastes

14. Functions of the Nephron • FILTRATION: in the glomerulus and Bowman’s capsule. • Driven by blood pressure • REABSORPTION: begins in proximal tubule • Salts, amino acids, sugars, vitamins • Water follows • Active Transport & Osmosis • Tubular SECRETION into the distal tubule • K+, H+, drugs, NH3 • Products are removed via excretion http://www.youtube.com/watch?v=glu0dzK4dbU http://www.youtube.com/watch?NR=1&v=aQZaNXNroVY&feature=fvwp http://www.youtube.com/watch?v=3THZeaMfuSw&NR=1&feature=endscreen

16. 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.

17. CONTROL OF THE KIDNEY • ADH: Antidiuretic Hormone: • “Against peeing” • Blood pressure is low due to dehydration • Sensed by hypothalamus in brain • stimulates pituitary gland to release ADH (travels to kidney) • Water is reabsorbed into blood from distal tubule • Blood pressure increases •  water in blood =  blood volume =  pressure = ADH presence is reduced

18. CONTROL OF THE KIDNEY • Aldosterone (adrenal hormone) • Controls excretion of Na+ and K+ • High [K+] in blood aldosterone released by adrenal gland • Causes more secretion of K+ into nephron, lowering blood K+ and therefore aldosterone • Negative Feedback Regulation – substances inhibit their own formation

19. Production to Urine