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Osmoregulation and Disposal of Metabolic Wastes

This chapter explores the processes of osmoregulation and excretion and their contribution to fluid and electrolyte homeostasis. It discusses the benefits and costs of excreting different nitrogenous wastes and compares osmoconformers and osmoregulators. Additionally, it describes the functions of protonephridia, metanephridia, and Malpighian tubules. Furthermore, it explains the role of the vertebrate kidney in maintaining water and electrolyte balance and excreting metabolic wastes. Finally, it compares different adaptations for osmoregulation in freshwater fishes, marine bony fishes, sharks, marine mammals, and terrestrial vertebrates.

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Osmoregulation and Disposal of Metabolic Wastes

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  1. Osmoregulation and Disposal of Metabolic Wastes Chapter 47

  2. Learning Objective 1 • How do the processes of osmoregulationand excretioncontribute to fluid and electrolyte homeostasis?

  3. Fluid-Electrolyte Homeostasis • Osmoregulation • active regulation of osmotic pressure of body fluids • maintains fluid and electrolyte homeostasis • Excretion • process of ridding body of metabolic wastes

  4. Learning Objective 2 • Contrast the benefits and costs of excreting ammonia, uric acid, or urea

  5. Nitrogenous Wastes • Ammonia (toxic) • excreted mainly by aquatic animals • Urea (less toxic) • synthesis requires energy • excretion requires water • Uric acid (less toxic) • excreted as semisolid paste (conserves water)

  6. Nitrogenous Wastes

  7. Amino acids Nucleic acids Deamination Keto acids Purines Ammonia Urea cycle 15 steps Ammonia Urea Uric acid More energy needed to produce More water needed to excrete Fig. 47-1, p. 1013

  8. Nucleic acids Amino acids Deamination Keto acids Purines Ammonia Urea cycle 15 steps Ammonia Urea Uric acid More energy needed to produce More water needed to excrete Stepped Art Fig. 47-1, p. 1013

  9. Learning Objective 3 • Compare osmoconformers and osmoregulators

  10. Osmoconformers • Most marine invertebrates • Salt concentration of body fluids varies with changes in sea water

  11. Osmoregulators • Some marine invertebrates • especially in coastal habitats • Maintain optimal salt concentration despite changes in salinity of surroundings

  12. KEY CONCEPTS • Osmoregulation is the process by which organisms control the concentration of water and salt in the body so that their body fluids do not become too dilute or too concentrated

  13. Learning Objective 4 • Describe protonephridia, metanephridia, and Malpighian tubules • Compare their functions

  14. Nephridial Organs • Help maintain homeostasis • by regulating concentration of body fluids • osmoregulation • excretion of metabolic wastes

  15. Protonephridia • Tubules with no internal openings • in flatworms and nemerteans • Interstitial fluid enters blind ends • flame cells (cells with brushes of cilia) • Cilia propel fluid through tubules • Excess fluid exits through nephridiopores

  16. Protonephridia

  17. Flame cells Protonephridial network Nephridiopores Excretory tubule Flatworm Fig. 47-2ab, p. 1014

  18. Nucleus Cytoplasm Cilia (“flame”) Movement of interstitial fluid Excretory tubule Fig. 47-2c, p. 1014

  19. Metanephridia • Tubules open at both ends • in most annelids and mollusks • Fluid from coelom moves through tubule • needed materials reabsorbed by capillaries • Urine exits body through nephridiopores • contains wastes

  20. Metanephridia

  21. Tubule Anterior Posterior Gut Funnel Capillary network Septum Nephridiopore Fig. 47-3, p. 1014

  22. Malpighian Tubules 1 • Extensions of insect gut wall • blind ends lie in hemocoel • Tubule cells actively transport uric acid from hemolymph into tubule • water follows by diffusion • Contents of tubule pass into gut

  23. Malpighian Tubules 2 • Water and some solutes reabsorbed in rectum • Malpighian tubules effectively conserve water • contribute to success of insects as terrestrial animals

  24. Malpighian Tubules

  25. Gut Malpighian tubules Waste Rectum Hindgut Midgut Water and needed ions Fig. 47-4, p. 1014

  26. KEY CONCEPTS • Excretory systems have evolved that function in both osmoregulation and in disposal of metabolic wastes

  27. Learning Objective 5 • Relate the function of the vertebrate kidney to the success of vertebrates in a wide variety of habitats

  28. The VertebrateKidney • Excretes nitrogenous wastes • Helps maintain fluid balance by adjusting salt and water content of urine

  29. Adaptation to Habitats • Freshwater, marine, terrestrial habitats • different problems for maintaining internal fluid balance, excretion of nitrogenous wastes • Structure and function of vertebrate kidney • adapted to various osmotic challenges of different habitats

  30. KEY CONCEPTS • The vertebrate kidney maintains water and electrolyte balance and excretes metabolic wastes

  31. Learning Objective 6 • Compare adaptations for osmoregulation in freshwater fishes, marine bony fishes, sharks, marine mammals, and terrestrial vertebrates

  32. Freshwater Fishes • Take in water osmotically • excrete large volume of hypotonic urine

  33. Loses salt by diffusion Water gain by osmosis Drinks no water Salt uptake by gills Large volume of hypotonic urine Kidney with large glomeruli Fig. 47-5a, p. 1015

  34. Marine Bony Fishes • Lose water osmotically • Compensate by drinking sea water and excreting salt through their gills • Produce only a small volume of isotonic urine

  35. Gains salts by diffusion Water loss by osmosis Drinks salt water Small volume of isotonic urine Salt excreted through gills Kidney with small or no glomeruli Fig. 47-5b, p. 1015

  36. Sharks and Other Marine Cartilaginous Fishes • Retain large amounts of urea • allows them to take in water osmotically through their gills • Excrete large volume of hypotonic urine

  37. Water gain by osmosis Salt-excreting gland Salts diffuse in through gills Some salt water swallowed with food Large volume of hypotonic urine Kidney with large glomeruli—reabsorbs urea Fig. 47-5c, p. 1015

  38. Marine Mammals • Ingest sea water with their food • produce concentrated urine

  39. Terrestrial Vertebrates • Must conserve water • adaptations include efficient kidneys • Endotherms • have a high metabolic rate • produce large volume of nitrogenous wastes

  40. LIVER ALL CELLS Hemoglobin breakdown Wastes produced Breakdown of nucleic acids Cellular respiration Deamination of amino acids Uric acid Water Bile pigments Carbon dioxide Wastes Urea Organs of excretion SKIN KIDNEY LUNGS DIGESTIVE SYSTEM Exhaled air containing water vapor and carbon dioxide Excretion Sweat Urine Feces Fig. 47-6b, p. 1016

  41. KEY CONCEPTS • Freshwater, marine, and terrestrial animals have different adaptations to meet the challenges of these diverse environments

  42. Learning Objective 7 • Describe (or label on a diagram) the organs of the mammalian urinary system • Give the functions of each

  43. The Urinary System • Principal excretory system in mammals • Mammalian kidneys produce urine • passes through ureters • to urinary bladder for storage • Urine is released from the body (urination) • through the urethra

  44. Human Urinary System

  45. Adrenal gland Right kidney Left renal artery Right renal vein Left kidney Inferior vena cava Abdominal aorta Ureteral orifices Right and left ureters Urinary bladder Urethra External urethral orifice Fig. 47-7, p. 1017

  46. Kidney Structure 1 • Renal cortex • outer portion of kidney • Renal medulla • inner portion of kidney • contains 8 to 10 renal pyramids • Renal pyramids • tip of each pyramid is a renal papilla

  47. Kidney Structure 2 • Urine flows into collecting ducts • which empty through a renal papilla into the renal pelvis (funnel-shaped chamber) • Nephrons • functional units of kidney • each kidney has more than 1 million

  48. Internal Kidney Structure

  49. Renal pyramids (medulla) Capsule Renal cortex Renal medulla Renal artery Renal vein Renal pelvis Ureter Internal structure of the kidney. Fig. 47-8a, p. 1018

  50. Distal convoluted tubule Juxtamedullary nephron Cortical nephron Capsule Proximal convoluted tubule Renal cortex Glomerulus Bowman’s capsule Artery and vein Loop of Henle Renal medulla Collecting duct Papilla Juxtamedullary and cortical nephrons. Fig. 47-8b, p. 1018

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