Water Balance & Excretion

1. Water Balance & Excretion

2. Osmoregulation • active regulation of the osmotic pressure of bodily fluids and cells • osmotic pressure = pressure resulting from a difference in solute concentration across a selectively permeable membrane

3. Osmoregulation • hyperosmotic • hypoosmotic • isoosmotic

4. Unicellular Organisms • water balance is often maintained by contractile vacuoles • video of Paramecium: http://www.youtube.com/watch?v=mTXRcbjuYGU

5. Excretion • eliminating waste is important for all living organisms

6. Types of Waste • wastes are eliminated through various organs: • lungs (CO2) • large intestine (solid wastes) • liver (transforms toxins for removal) • kidneys (soluble wastes)

7. Nitrogenous Wastes • mostly from deamination • animals that live in water can remove ammonia with lots of water • mammals, some reptiles, most amphibians form urea • birds and some invertebrates produce uric acid

8. Human Excretory System

9. Renal Blood Flow) • blood is brought to the kidneys by the renalarteries • filtered blood leaves the kidneys through the renalveins

10. The Urinary System • kidneys can hold up to 25% of the body’s blood at a time • kidneys filter the blood • urine (with wastes and toxins) is conducted to the bladder through the ureters

11. Kidney Structure Basic structure: • cortex • medulla • renal pelvis

12. Nephron • the functional unit of the kidney is the nephron • there are about 1 million nephrons in each kidney

14. Review Kidney Structure…

16. Be able to label

17. Label the diagram

18. Explain the production of Urine

19. How is urine formed?

20. Urine Formation • filtration • reabsorption • secretion • Simple overview of urine formation: • http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000136&ptid=17

21. Filtration • higher blood pressure in glomerulus • water, ions, smaller dissolved molecules (glucose, amino acids, urea) can move through the walls of the glomerulus • your kidneys filter your entire blood plasma 65 times every day!

22. Reabsorption • ion pumps reabsorb Na+, K+, Cl- (active) • active transport proteins reabsorb amino acids, glucose • filtrate becomes hypoosmotic to interstitial fluid, so water is reabsorbed by osmosis and through aquaporins

23. Where? • a lot of reabsorption occurs in the proximal convoluted tubule • filtrate with high concentration of urea and other wastes enters loop of Henle and then distal convoluted tubule: • more water and ions (Na+& Cl-)are reabsorbed

24. Where (cont’d)? • collecting ducts are permeable to water but not salt ions, so more water is reabsorbed • at bottom of medulla, urea is reabsorbed through passive urea transporters (increasing concentration gradient…more water reabsorbed)

25. Secretion • H+ ions (active) to adjust blood pH (HCO3- is also reabsorbed to balance) • products of detoxified poisons (passive) • water-soluble drugs (passive) • nitrogen-containing wastes (such as small amounts of NH3) • in the proximal and distal convoluted tubules

26. Animations • Narrated animation on urine formation; good amount of detail: • http://davisplus.fadavis.com/scanlon6e/Animations/animations.cfm?exercise=NephronFiltration&title=Nephron%20Filtration • Narrated animation of structure & function; quite detailed: • http://bcs.whfreeman.com/thelifewire/content/chp51/51020.html

27. Other links… • Khan academy…this video starts off with the structure of the kidney & nephron, then goes into detail about the formation of urine (covered in 9.5) • http://www.khanacademy.org/video/the-kidney-and-nephron?playlist=Biology