1. Fluid Balance/ Nitrogen Excretion Kidney Function

2. Salt/Water Balance ionic composition of cytosol is maintained by osmotic interaction with intercellular fluid intercellular fluid is conditioned by osmotic interaction with capillary contents excretory organs control the osmotic composition of blood –differentially excrete different compounds –excrete nitrogenous wastes from terrestrial animals

3. Salt/Water Balance common mechanisms of excretory organs –filtration movement of water and solutes out of capillary under pressure –secretion active transport of additional molecules into filtrate –resorption active uptake of solutes from filtrate

4. Salt/Water Balance diverse challenges of different environments –osmotic potentials of aquatic environments vary dramatically marine: 1070 mosmol/L fresh water: 1-10 mosmol/L –physiological responses to different environmental osmolarities vary

5. Salt/Water Balance physiological responses to different environmental osmolarities –osmoconformers do not regulate tissue fluid osmolarity ionic conformers –same ionic composition as ambient ionic regulators –modify ionic composition but not overall osmolarity

6. Salt/Water Balance physiological responses to different environmental osmolarities –osmoregulators maintain tissue fluid osmolarity different from environmental hypotonic osmoregulators –marine organisms –excrete salt; conserve water hypertonic osmoregulators –fresh water organisms –excrete water; conserve salt

7. three osmoregulatory modes Figure 51.1

8. Salt/Water Balance physiological responses to different environmental osmolarities –terrestrial organisms conserve water & salt

9. Nitrogenous Wastes are Excreted catabolism of amino acids & nucleotides produces nitrogenous waste –ammonia (NH 3 ) is quite toxic ammonotelic organisms lose NH 3 to aqueous environment across gills ureotelic organisms convert NH 3 to urea –highly water soluble uricotelic organisms covert NH 3 to uric acid –slightly water soluble

10. Three N Excretion Forms Figure 51.3

11. Invertebrate Excretory Systems protonephridia –in flatworms –flame cell + tubule tissue fluid enters flame cell lumen cilia drive fluid toward excretory pore tubule cells modify fluid composition urine is less concentrated than tissue fluid

12. protonephridia in Planaria Figure 51.4

13. Invertebrate Excretory Systems metanephridia –annelid worms fluid-filled coelom in each body segment closed circulatory system –filtration from blood into coelom –diffusion of waste products into coelom

14. circulatory/excretory interaction in earthworm Figure 51.5

15. Invertebrate Excretory Systems metanephridia –annelid worms metanephridia occupy adjacent segments –nephrostome collects coelomic fluid –tubule travels to adjacent segment –tubule cells resorb & secrete compounds –dilute urine leaves a nephridiopore

16. Invertebrate Excretory Systems Malpighian tubules - insects –join gut between midgut & hindgut –extend into body tissues –actively transport uric acid, K +, Na + from hemolymph –take water into tubules by osmosis –muscular contractions propel toward gut –hindgut returns Na +, K + to tissue fluid; water follows –uric acid precipitates in rectum

17. Malpighian tubule Figure 51.6

18. Vertebrate Excretory Systems nephron (functional unit of kidney) –an afferent arteriole branches into a dense capillary bed = the glomerulus –the glomerulus is surrounded by Bowman’s capsule (= renal corpuscle) –blood is filtered from the glomerulus through podocyte “fingers” into Bowman’s capsule

19. nephron anatomy Figure 51/8

20. renal filtration Figure 51.7

21. Vertebrate Excretory Systems nephron –glomerular capillaries combine into an efferent arteriole –the efferent arteriole branches into a peritubular capillary bed –the renal tubule modifies fluid composition resorption & secretion –peritubular capillaries deliver materials to be secreted into urine take up resorbed materials

22. tubular modification of fluid contents Figure 51.7

23. Vertebrate Excretory Systems nephron –peritubular capillaries combines into a renal venule –the renal tubule delivers urine to a collecting duct

24. fluid collection Figure 51.7

25. vertebrate nephron Figure 51/7

26. Vertebrate Excretory Systems nephrons of different vertebrates accomplish different tasks –water excretion; salt conservation –water conservation; salt excretion

27. Vertebrate Excretory Systems marine bony fishes –secrete salts; conserve water hypotonic osmoregulation fewer glomeruli - limits volume of urine excrete Na +, Cl -, NH 3, through renal tubules & gills do not absorb some ions from gut

28. Vertebrate Excretory Systems cartilaginous fishes –ionic regulating osmoconformers N waste retained as urea special salt-secreting sites remove excess dietary NaCl

29. Vertebrate Excretory Systems amphibians –conserve salt; excrete water, OR –conserve both reduce skin permeability estivate during hot dry periods

30. Vertebrate Excretory Systems reptiles & birds –conserve water & salt minimize skin evaporation limit water loss by excreting uric acid

31. Vertebrate Excretory Systems mammals –conserve water, regulate ions excrete urine hypertonic to tissue fluids kidney concentrates urine

32. human urinary system; kidney anatomy Figure 51.9

33. human kidney nephron components & arrangement - tubule –Bowman’s capsule - cortex –proximal convoluted tubule - cortex –loop of Henle - descending/ascending in medulla –distal convoluted tubule - cortex –collecting duct - cortex => medulla

34. renal pyramid Figure 51.9

35. human kidney nephron components & arrangement - vessels –afferent arteriole supplies glomerulus –efferent arteriole branches into peritubular capillaries –vasa recta capillary bed parallels loop of Henle –peritubular capillaries join to form the venule that empties into the renal vein –~98% of filtrate leaves kidney in renal vein

36. human kidney nephron function –glomerulus filters plasma into Bowman’s capsule –proximal convoluted tubule transports Na +, glucose, amino acids, etc. into tissue fluid –water moves out of tubule by osmosis –peritubular venous capillaries take up water and molecules –tubule contents enter loop of Henle at an osmotic potential similar to plasma

37. human kidney nephron function –urine concentration in loop of Henle thin descending limb –permeable to water –impermeable to Na +, Cl -

38. thin descending limb loses water, retains NaCl Figure 51.10

39. thin ascending limb loses NaCl, retains water Figure 51.10

40. human kidney nephron function –urine concentration in loop of Henle thin descending limb thin ascending limb thick ascending limb –impermeable to water –actively transports Cl - out, Na + follows

41. thick ascending limb pumps out NaCl, retains water Figure 51.10

42. human kidney nephron function –thick ascending limb increases solute in tissue fluid –thin ascending limb increases solute in tissue fluid –thin descending limb contents become increasingly concentrated –dilute fluid enters distal convoluted tubule –osmosis empties distal convoluted tubule until osmotic potential is same as plasma

43. human kidney nephron function –the loop of Henle creates a concentration gradient in the medulla –vasa recta removes water from medulla –collecting duct passes through the medulla water leaves the duct by osmosis highly concentrated urine is produced

44. nephron function in the human kidney Figure 51.10

45. nephron function blood plasma is filtered into tubule ions are actively resorbed a concentration gradient is established in the medulla water is reclaimed by osmosis

46. Control & Regulation of Kidney Function Glomerular Filtration Rate depends on blood pressure and blood volume autoregulatory renal responses –reduced blood pressure causes afferent arteriole dilation –continued low GFR causes release of renin which activates circulating angiotensin

47. Control & Regulation of Kidney Function autoregulatory renal responses –continued low GFR causes release of renin which activates circulating angiotensin efferent arteriole constriction systemic peripheral vessel constriction release of aldosterone from adrenal cortex –stimulates Na + resorption ( & so H 2 O) –stimulates thirst

48. Control & Regulation of Kidney Function Glomerular Filtration Rate depends on blood pressure and blood volume antidiuretic hormone (ADH) control –ADH release increases as aortic stretch signals decrease or as osmolarity increases increases permeability of collecting ducts to water increases blood volume decreases osmolarity

49. control & regulation of kidney function Figure 51/14