1. Osmoregulation
Chapter 44

2. Homeostasis Homeostasis – maintaining an internal steady state
Osmoregulation – maintaining a water and solute balance; rates of water uptake and loss must balance
Excretion – removing metabolic wastes

3. Water Balance

4. Osmolarity
Osmotic pressure or the total solute concentration (expressed in moles of solute/liter of solution)
When two solutes are separated by a selectively permeable membrane they will be: isoosmotic, hyperosmotic or hypoosmotic to each other

5. When comparing two solutions…

6. To conform or not to conform…
Osmoconformers – does not actively adjust to its internal osmolarity, ectoderms ex: marine animals that are isoosmotic to the water
Osmoregulators – must control their osmolarity because it is not isoosmotic to its surroundings, endotherms ex: freshwater or terrestrial animals

7. Marine Animals Need Salt Excretory Glands
Most fish are hypoosmotic to the ocean water-therefore they lose water and gain salt from the ocean
To replenish, they drink seawater then remove the salt through their gills or salt glands (in birds)

8. Freshwater Animals Consistently gain water and lose salt
They have no need to drink sea water like the marine animals
Therefore they excrete large amounts of water in dilute urine and take up salt through their gills

9. What about Salmon??
Salmon survive in both marine and freshwater environments. How??

10. The Nitrogenous Wastes
N wastes come from the metabolism of protein and nucleic acids
The form of N waste the animal removes is influenced by the environment it lives in

11. The type of excretion
Ammonia – the end product of protein and nucleic acid breakdown, extremely toxic, aquatic animals excrete ammonia into the water (gets diluted immediately) ex: fish
Urea – ammonia gets transformed into urea in the liver then removed through urine ex: mammals
Uric Acid – ammonia gets transformed into uric acid (a paste) to conserve the most water ex: insects and birds

12. General Excretory System Function
Filtration – body fluid is filtered
Reabsorption – important and usable molecules are reabsorbed to the body fluid
Secretion – remaining toxins are actively transported into the tubule
Excretion – wastes are removed

13. Protonephridria - Planarian
Flame bulb has cilia that bring water and solutes into tubules called protonephridia –
Wastes empty into the external environment through nephridiopores

14. Metanephridia - Earthworm
Cilia  metanephridia filters and reabsorbs  wastes empty through nephridiopore

15. Malpighian Tubules - Grasshopper
Insects secrete wastes and salts from hemolymph into Malpighian tubules
Water follows by osmosis
Salt and water are reabsorbed across rectum and wastes are eliminated with feces

16. Mammalian Excretory System
Skin
Liver
Kidney (urinary system)

17. The Urinary System
Urinary System composed of the kidney, 2 ureters, bladder and urethra
Urinary System filters blood (excretion) and aids in osmoregulation

18. The Kidney Part of the urinary system
Supplied with blood through the renal artery and removed through the renal vein
2 regions – outer renal cortex and inner renal medulla
Filters blood through nephrons (about 1 million each) – produce urine that is hyperosmotic to body fluids (water conservation)

19. The Nephron Surrounded by capillaries Glomerulus – ball of capillaries
Bowman’s Capsule – cup-shaped end of tubule, surrounds the glomerulus - FILTRATION
Proximal Tube, Loop of Henle, Distal Tube – REABSORPTION AND SECRETION
Collecting Duct - EXCRETION

20. The Mammalian Excretory System

21. Regional Functions of Nephron
1. Filtrate
2. Reabsorption of water by passive transport
3. High water content due to passive and active transport of NaCl
4. Reabsorption and secretion to regulate pH, NaCl, and K+
5. Active reabsorption of salt, causes reabsorption of water

22. Urine Concentration through a two solute model
Low Salt; High Water
High Salt; Low Water

23. Hormonal Control of the Kidney
Negative feedback
High salt or low water  ADH (anti-diuretic hormone) increases water absorption
Reduced BP Renin, angiotensinogen, aldosterone increases arteriole constriction
Increased BP ANF (atrial natriuretic factor) inhibits release of renin

24. Hormonal Regulation