Biology 201 Dr. Edwin DeMont

1. Biology 201Dr. Edwin DeMont Body Fluid Regulation St. Francis Xavier University

2. Osmoregulation Excretion of is usually associated with the regulation of water and solute (ionic) balance through a physiological process called osmoregulation. Osmosis is associated with the movement of water down its concentration gradients. St. Francis Xavier University

3. Osmosis Demonstration St. Francis Xavier University

4. Aquatic animals Osmoregulation is an important concern for aquatic animals – which are surrounded by water. Large differences in the process for marine or fresh water animals. St. Francis Xavier University

5. Osmosis : Marine Animals Water tends to move out of Fish Sugar = ions W F W F St. Francis Xavier University

6. Osmoregulators Salt water fish and Ammonia Water tends to move out of Fish St. Francis Xavier University

7. Osmosis : Fresh water Fish Water tends to move intoFish Sugar = ions F W F W St. Francis Xavier University

8. Osmoregulators Fresh water fish and Ammonia Water tends to move intoFish St. Francis Xavier University

9. Invertebrate Excretory Systems Water tends to move into animal. Demonstration Fresh water flatworm: - Nitrogenous wastes diffuse across body surface- Flame cells eliminate excess water St. Francis Xavier University

10. Excretion Excretion is the elimination of metabolic waste products such as carbon dioxide, water, nitrogen and ions. Protein metabolism produces various nitrogenous wastes. St. Francis Xavier University

11. Nitrogen Metabolism Amino acid metabolism yields ammonia (NH3) Ammonia alters acid-base balance as it binds to protons and becomes ammonium ion (NH4+) Ammonium ion can be toxic Interferes with Na+/K+ ATPase transporters of cell membranes by substituting for K+ • Ammonia or ammonium ions must be highly diluted and rapidly excreted; • or be converted to less toxic forms: urea or uric acid. St. Francis Xavier University

12. Ammonia Most aquatic animals – including most bony fishes and most invertebrates rely on ammonia excretion, usually via gills. This works because:1. Water outside the animal is plentiful to dilute ammonia2. Molecule is small and uncharged so readily penetrates most membranes. Most terrestrial animals do not have this option so convert ammonia to urea or uric acid (usually in the liver) and transport to the excretory organs. St. Francis Xavier University

13. Urea Urea is the primary nitrogenous waste of most adult amphibians and mammals. Urea is produced from two ammonium ions and a bicarbonate ion using ATP. Urea is 10 – 100 times less toxic than ammonia and when it is removed takes two nitrogens per molecule. St. Francis Xavier University

14. Uric Acid In other terrestrial animals – insects, birds and most reptiles uric acid is usually the primary nitrogenous waste. Production of uric acid is more metabolically expensive to produce than urea but is less toxic because it is highly insoluble, removes four nitrogens per molecule and is excreted in a semisolid form. St. Francis Xavier University

15. Invertebrate Excretory Systems St. Francis Xavier University

16. Invertebrate Excretory Systems • Initiated by K+ secretion into lumen • Fluid more +ve so Cl- attracted • KCl makes tubule fluid concentrated so water moves in via osmosis. • Infusion of water generates a bulk flow down the tubule • Metabolic wastes such as uric acid secreted and transported down system St. Francis Xavier University

17. Urinary System St. Francis Xavier University

18. Anatomy: Nephron St. Francis Xavier University

19. Vertebrate Excretory Systems Glomerulus – filtration apparatus Walls of capillaries contain small perforations that as as filters. Blood pressure forces fluid through the slits. The filtrate contains small molecules, ions and the primary nitrogenous wastes either uric acid or urea. Large proteins and blood cells do not get filtered. St. Francis Xavier University

20. Physiology: Countercurrent Overview Osmosis St. Francis Xavier University