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Ch. 44

Osmoregulation and Excretion. Ch. 44. A Balancing Act. Maintaining the fluid environment of cells, tissues, and organs is critical Achieved by… Osmoregulation General term for the processes by which animals control solute concentrations and balance water gain and loss Excretion

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Ch. 44

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  1. Osmoregulation and Excretion Ch. 44

  2. A Balancing Act Maintaining the fluid environment of cells, tissues, and organs is critical Achieved by… • Osmoregulation • General term for the processes by which animals control solute concentrations and balance water gain and loss • Excretion • Process that rids the body of nitrogenous metabolites and other metabolic waste products

  3. Osmosis and Osmolarity Osmolarity • Total solute concentration expressed as molarity (mols of solute/liter of solution) • Isoosmotic • Equal concentrations • Hyperosmotic • The solution with greater solute • Hypoosmotic • The solution with less solute

  4. Osmotic Challenges Osmoconformer • Isoosmotic with surroundings • Marine animals Osmoregulator • Control internal osmolarity independent of the environment • Freshwater and terrestrial habitats Stenohaline vs. Euryhaline

  5. Animals that Live in Waters

  6. Animals that Live in Temporary Waters Desiccation • Extreme dehydration is fatal for most animals Anhydrobiosis • Dormant state due to drying up of their habitat • Tardigrades (water bears)

  7. Land Animals Body coverings prevent dehydration • Waxy exoskeletons, shells, keratinized skin Mainly lose water by… • Urine and feces • Across the skin • Surfaces of gas exchange organs

  8. Forms of Nitrogenous Wastes Ammonia • aquatic animals • Mainly excreted by the gills; little by the kidney • unsuitable for terrestrial b/c it requires lots of water and is extremely toxic if not excreted quickly Urea • Low toxicity but energy costly • ammonia combines with CO2 in the liver

  9. Forms of Nitrogenous Wastes Uric acid • land snails, insects, birds, and many reptiles • Relatively nontoxic but the most costly in energy • much less soluble in water • usually eliminated in a pastelike form along with feces

  10. Excretory System

  11. Diversity of Excretory Systems Flatworms • have neither a circulatory system or coelom • protonephridium instead Protonephridium • network of closed tubules lacking internal openings that branch throughout the body • smallest branches capped by flame bulbs

  12. Diversity of Excretory Systems Metanephridia • most annelids • excretory tubules in each segment that have internal openings to collect body fluids • capillaries surround the metanephridium • empties outside the body through the nephridiopore

  13. Diversity of Excretory Systems Malpighian tubules • insects, terrestrial arthropods • remove nitrogenous wastes from the hemolymph • empties via the rectum

  14. Excretory Systems Urine production – 2 steps • Filtration of body fluids • Modification of filtrate • selective reabsorption of solutes from the filtrate back into body fluids • selective secretion of solutes from body fluids into the filtrate

  15. Excretory Processes • Filtration • Water and solutes are forced by pressure out of the blood and into the excretory tubule • Reabsorption • Valuable substances are transported from the filtrate back to body fluids • Secretion • Excretion

  16. Excretory Processes • Filtration • Reabsorption • Secretion • toxins, and excess ions are extracted from body fluids and added to the excretory tubule • Excretion • Altered filtrate (urine) leaves the system and the body

  17. Diversity of Excretory Systems Vertebrate kidneys • compact organs • large numbers of non-segmentally arranged tubules • dense capillary network

  18. Mammalian Kidneys Pair of bean shaped organs • 10 cm long Renal artery • blood enters the kidney Renal vein • blood exits the kidney Urine  ureter  u. bladder  urethra (sphincter muscles control urination)

  19. Mammalian Kidneys • Renal cortex and renal medulla Nephrons • functional unit of the kidney • long tubule with associated capillaries Urine formation • Filtration • Reabsorption • Secretion

  20. Mammalian Kidneys

  21. Filtration • Blood pressure forces fluid (water, salts, urea, and other small molecules) into the kidneys (nephrons) • Capillaries nonselectively filter out blood cells and large molecules • Small molecules enter the nephron • Filtrate produced • glucose, salts, vitamins, nitrogenous wastes, and small molecules

  22. Reabsorption • Selective transport of filtrate substances back into the interstitial fluid • Reclaims essential small molecules • sugars, vitamins, organic nutrients, water • Beneficial substances back into body and nonuseful and waste substances into kidneys for excretion

  23. Secretion • Plasma is added to the filtrate • Very selective process • utilizes both active and passive transport • Collecting duct receives processed filtrate and transfers urine to renal pelvis

  24. A Closer Look at the Nephron Proximal Tubule • Reabsorption of ions Descending Loop of Henle • Reabsorption of H2O (aquaporins) Ascending Loop of Henle • Impermeable to water, NaCl leaves Distal tubule • Regulates K+ and NaCl concentrations Collecting duct • Sends urine to renal pelvis • Some water reabsorption

  25. Adaptations of the Vertebrate Kidney to Diverse Environments Mammals  Nephrons ability to get rid of waste and not squander water Extra long loop of Henle producing extremely concentrated urine Short loops for aquatic mammals Reptiles  Nephrons to conserve water Uric acid is the main nitrogen waste molecule Cloaca

  26. Adaptations of the Vertebrate Kidney to Diverse Environments Freshwater Fishes and Amphibians  Many nephrons and long loop of Henle Must secrete excess water continuously Produce filtrate at a high rate Marine Bony Fishes  Few and small nephrons lacking a distal tubule Low filtration rate…small glomeruli

  27. Hormonal Circuits (negative feedback and transduction pathways) - ADH

  28. Hormonal Circuits – Renin-Angiotensin-Aldosterone System JGA- Network of specialized tissues of cells and around afferent arteriole; supplies blood to glomerulus; releases renin

  29. Summary

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