1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 44 Osmoregulation and Excretion

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: A Balancing Act Physiological systems of animals operate in a fluid environment Relative concentrations of water and solutes must be maintained within fairly narrow limits

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Freshwater animals show adaptations that reduce water uptake and conserve solutes Desert and marine animals face desiccating environments that can quickly deplete body water

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

5. Osmoregulation regulates solute concentrations and balances the gain and loss of water Excretion gets rid of metabolic wastes

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 44.1: Osmoregulation balances the uptake and loss of water and solutes Osmoregulation is based largely on controlled movement of solutes between internal fluids and the external environment

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Osmosis Cells require a balance between osmotic gain and loss of water Various mechanisms of osmoregulation in different environments balance water uptake and loss

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Osmotic Challenges Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity Euryhaline animals can survive large fluctuations in external osmolarity

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

11. Marine Animals Most marine invertebrates are osmoconformers Most marine vertebrates and some invertebrates are osmoregulators

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Marine bony fishes are hypoosmotic to sea water They lose water by osmosis and gain salt by diffusion and from food They balance water loss by drinking seawater

13. LE 44-3a Gain of water and salt ions from food and by drinking seawater Osmotic water loss through gills and other parts of body surface Excretion of salt ions from gills Osmoregulation in a saltwater fish Excretion of salt ions and small amounts of water in scanty urine from kidneys

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Freshwater Animals Freshwater animals constantly take in water from their hypoosmotic environment They lose salts by diffusion and maintain water balance by excreting large amounts of dilute urine Salts lost by diffusion are replaced by foods and uptake across the gills

15. LE 44-3b Excretion of large amounts of water in dilute urine from kidneys Osmotic water gain through gills and other parts of body surface Osmoregulation in a freshwater fish Uptake of salt ions by gills Uptake of water and some ions in food

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animals That Live in Temporary Waters Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state This adaptation is called anhydrobiosis

17. LE 44-4 Hydrated tardigrade Dehydrated tardigrade 100 µm

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Land Animals Land animals manage water budgets by drinking and eating moist foods and using metabolic water

19. LE 44-5 Water balance in a kangaroo rat (2 mL/day) Water balance in a human (2,500 mL/day) Water gain Water loss Derived from metabolism (1.8 mL) Ingested in food (0.2 mL) Derived from metabolism (250 mL) Ingested in food (750 mL) Ingested in liquid (1,500 mL) Evaporation (900 mL) Feces (100 mL) Urine (1,500 mL) Evaporation (1.46 mL) Feces (0.09 mL) Urine (0.45 mL)

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Desert animals get major water savings from simple anatomical features

21. LE 44-6 Control group (Unclipped fur) Experimental group (Clipped fur) Water lost per day (L/100 kg body mass) 4 3 2 1 0

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Transport Epithelia Transport epithelia are specialized cells that regulate solute movement They are essential components of osmotic regulation and metabolic waste disposal They are arranged in complex tubular networks An example is in salt glands of marine birds, which remove excess sodium chloride from the blood

23. LE 44-7a Nostril with salt secretions Nasal salt gland

24. LE 44-7b Vein Capillary Secretory tubule Transport epithelium Direction of salt movement Central duct Artery Blood flow Lumen of secretory tubule NaCl Secretory cell of transport epithelium

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 44.2: An animal’s nitrogenous wastes reflect its phylogeny and habitat The type and quantity of an animal’s waste products may greatly affect its water balance Among the most important wastes are nitrogenous breakdown products of proteins and nucleic acids

26. LE 44-8 Nitrogenous bases Nucleic acids Amino acids Proteins —NH 2 Amino groups Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails AmmoniaUreaUric acid

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Forms of Nitrogenous Wastes Different animals excrete nitrogenous wastes in different forms: ammonia, urea, or uric acid

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ammonia Animals that excrete nitrogenous wastes as ammonia need lots of water They release ammonia across the whole body surface or through gills

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Urea The liver of mammals and most adult amphibians converts ammonia to less toxic urea The circulatory system carries urea to the kidneys, where it is excreted

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Uric Acid Insects, land snails, and many reptiles, including birds, mainly excrete uric acid Uric acid is largely insoluble in water and can be secreted as a paste with little water loss

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Influence of Evolution and Environment on Nitrogenous Wastes The kinds of nitrogenous wastes excreted depend on an animal’s evolutionary history and habitat The amount of nitrogenous waste is coupled to the animal’s energy budget

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 44.3: Diverse excretory systems are variations on a tubular theme Excretory systems regulate solute movement between internal fluids and the external environment

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Excretory Processes Most excretory systems produce urine by refining a filtrate derived from body fluids Key functions of most excretory systems: – Filtration: pressure-filtering of body fluids – Reabsorption: reclaiming valuable solutes – Secretion: adding toxins and other solutes from the body fluids to the filtrate – Excretion: removing the filtrate from the system

34. LE 44-9 Filtration Reabsorption Secretion Excretion Excretory tubule Capillary Filtrate Urine

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survey of Excretory Systems Systems that perform basic excretory functions vary widely among animal groups They usually involve a complex network of tubules

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protonephridia: Flame-Bulb Systems A protonephridium is a network of dead-end tubules lacking internal openings The smallest branches of the network are capped by a cellular unit called a flame bulb These tubules excrete a dilute fluid and function in osmoregulation

37. LE 44-10 Protonephridia (tubules) Tubule Nephridiopore in body wall Flame bulb Interstitial fluid filters through membrane where cap cell and tubule cell interdigitate (interlock) Tubule cell Cilia Nucleus of cap cell

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metanephridia Each segment of an earthworm has a pair of open-ended metanephridia Metanephridia consist of tubules that collect coelomic fluid and produce dilute urine for excretion

39. LE 44-11 Collecting tubule Nephridio- pore Capillary network Coelom Bladder Metanephridium Nephrostome

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Malpighian Tubules In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation Insects produce a relatively dry waste matter, an important adaptation to terrestrial life

41. LE 44-12 Salt, water, and nitrogenous wastes Digestive tract Midgut (stomach) Malpighian tubules Rectum Intestine Hindgut Reabsorption of H 2 O, ions, and valuable organic molecules Malpighian tubule HEMOLYMPH Anus Rectum Feces and urine

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vertebrate Kidneys Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 44.4: Nephrons and associated blood vessels are the functional unit of the mammalian kidney The mammalian excretory system centers on paired kidneys, which are also the principal site of water balance and salt regulation Each kidney is supplied with blood by a renal artery and drained by a renal vein Urine exits each kidney through a duct called the ureter Both ureters drain into a common urinary bladder Animation: Nephron Introduction Animation: Nephron Introduction

44. LE 44-13 Excretory organs and major associated blood vessels Renal medulla Renal cortex Renal pelvis Section of kidney from a rat Kidney structure Ureter Kidney Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Afferent arteriole from renal artery Efferent arteriole from glomerulus Distal tubule Collecting duct SEM 20 µm Branch of renal vein Filtrate and blood flow Vasa recta Descending limb Ascending limb Loop of Henle Renal medulla Nephron To renal pelvis Renal cortex Collecting duct Juxta- medullary nephron Cortical nephron Posterior vena cava Renal artery and vein Aorta Ureter Urinary bladder Urethra

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structure and Function of the Nephron and Associated Structures The mammalian kidney has two distinct regions: an outer renal cortex and an inner renal medulla

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The nephron, the functional unit of the vertebrate kidney, consists of a single long tubule and a ball of capillaries called the glomerulus

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Filtration of the Blood Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Filtration of small molecules is nonselective The filtrate in Bowman’s capsule mirrors the concentration of solutes in blood plasma

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pathway of the Filtrate From Bowman’s capsule, the filtrate passes through three regions of the nephron: the proximal tubule, the loop of Henle, and the distal tubule Fluid from several nephrons flows into a collecting duct

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Vessels Associated with the Nephrons Each nephron is supplied with blood by an afferent arteriole, a branch of the renal artery that divides into the capillaries The capillaries converge as they leave the glomerulus, forming an efferent arteriole The vessels divide again, forming the peritubular capillaries, which surround the proximal and distal tubules

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings From Blood Filtrate to Urine: A Closer Look Filtrate becomes urine as it flows through the mammalian nephron and collecting duct Secretion and reabsorption in the proximal tubule greatly alter the filtrate’s volume and composition Reabsorption of water continues as filtrate moves into the descending limb of the loop of Henle

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In the ascending limb of the loop of Henle, salt diffuses from the permeable tubule into the interstitial fluid The distal tubule regulates the K + and NaCl concentrations of body fluids The collecting duct carries filtrate through the medulla to the renal pelvis and reabsorbs NaCl

53. LE 44-14 Filtrate H 2 O Salts (NaCl and others) HCO 3 – H + Urea Glucose; amino acids Some drugs Key Active transport Passive transport INNER MEDULLA OUTER MEDULLA NaCl H2OH2O CORTEX Descending limb of loop of Henle Proximal tubule NaCl Nutrients HCO 3 – H+H+ K+K+ NH 3 H2OH2O Distal tubule NaCl HCO 3 – H+H+ K+K+ H2OH2O Thick segment of ascending limb NaCl Thin segment of ascending limb Collecting duct Urea H2OH2O

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Collecting Duct Animation: Collecting Duct Animation: Loop of Henle and Distal Tubule Animation: Loop of Henle and Distal Tubule Animation: Bowman's Capsule and Proximal Tubule Animation: Bowman's Capsule and Proximal Tubule

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 44.5: The mammalian kidney’s ability to conserve water is a key terrestrial adaptation The mammalian kidney conserves water by producing urine that is much more concentrated than body fluids

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Solute Gradients and Water Conservation The cooperative action and precise arrangement of the loops of Henle and collecting ducts are largely responsible for the osmotic gradient that concentrates the urine NaCl and urea contribute to the osmolarity of the interstitial fluid, which causes reabsorption of water in the kidney and concentrates the urine

57. LE 44-15_3 INNER MEDULLA OUTER MEDULLA CORTEX Osmolarity of interstitial fluid (mosm/L) NaCl Urea H2OH2O Active transport Passive transport 300 100 400 200 H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O 600 400 900 700 1200 300 400 H2OH2O 600 1200 600 900 300 400 NaCl Urea H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney This enables the kidney to form concentrated urine

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The collecting duct conducts filtrate through the osmolarity gradient, and more water exits the filtrate by osmosis Urea diffuses out of the collecting duct as it traverses the inner medulla Urea and NaCl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Regulation of Kidney Function The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys Antidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney Animation: Effect of ADH Animation: Effect of ADH

61. LE 44-16a Osmoreceptors in hypothalamus Hypothalamus ADH Pituitary gland Increased permeability Distal tubule Thirst Drinking reduces blood osmolarity to set point Collecting duct H 2 O reab- sorption helps prevent further osmolarity increase Homeostasis: Blood osmolarity STIMULUS The release of ADH is triggered when osmo- receptor cells in the hypothalamus detect an increase in the osmolarity of the blood

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The renin-angiotensin-aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis

63. LE 44-16b Distal tubule Aldosterone Homeostasis: Blood pressure, volume STIMULUS: The juxtaglomerular apparatus (JGA) responds to low blood volume or blood pressure (such as due to dehydration or loss of blood) Increased Na + and H 2 O reab- sorption in distal tubules Renin production Arteriole constriction Adrenal gland Angiotensin II Angiotensinogen JGA Renin

64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Another hormone, atrial natriuretic factor (ANF), opposes the RAAS

65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The South American vampire bat, which feeds on blood, has a unique excretory system Its kidneys offload much of the water absorbed from a meal by excreting dilute urine

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

67. Concept 44.6: Diverse adaptations of the vertebrate kidney have evolved in different environments The form and function of nephrons in various vertebrate classes are related to requirements for osmoregulation in the animal’s habitat

68. LE 44-18a Bannertail kangaroo rat (Dipodomys spectabilis) Beaver (Castor canadensis)

69. LE 44-18b Rainbow trout (Oncorrhynchus mykiss) Frog (Rana temporaria)

70. LE 44-18c Roadrunner (Geococcyx californianus) Desert iguana (Dipsosaurus dorsalis)

71. LE 44-18d Northern bluefin tuna (Thunnus thynnus)