LECTURE PRESENTATIONS For CAMPBELL BIOLOGY NINTH EDITION Jane
LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 44 Osmoregulation and Excretion Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.
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 • Osmoregulation regulates solute concentrations and balances the gain and loss of water © 2011 Pearson Education, Inc.
• Freshwater animals show adaptations that reduce water uptake and conserve solutes • Desert and marine animals face desiccating environments that can quickly deplete body water • Excretion gets rid of nitrogenous metabolites and other waste products © 2011 Pearson Education, Inc.
Figure 44. 1
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 © 2011 Pearson Education, Inc.
Osmosis and Osmolarity • Cells require a balance between uptake and loss of water • Osmolarity, the solute concentration of a solution, determines the movement of water across a selectively permeable membrane • If two solutions are isoosmotic, the movement of water is equal in both directions • If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution © 2011 Pearson Education, Inc.
Figure 44. 2 Selectively permeable membrane Solutes Water Hypoosmotic side: • Lower solute concentration • Higher free H 2 O concentration Hyperosmotic side: • Higher solute concentration • Lower free H 2 O concentration Net water flow
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 © 2011 Pearson Education, Inc.
• Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity • Euryhaline animals can survive large fluctuations in external osmolarity © 2011 Pearson Education, Inc.
Marine Animals • Most marine invertebrates are osmoconformers • Most marine vertebrates and some invertebrates are osmoregulators • Marine bony fishes are hypoosmotic to seawater • They lose water by osmosis and gain salt by diffusion and from food • They balance water loss by drinking seawater and excreting salts © 2011 Pearson Education, Inc.
Figure 44. 3 (a) Osmoregulation in a marine fish Gain of water and salt ions from food Gain of water and salt ions from drinking seawater Excretion of salt ions from gills Osmotic water loss through gills and other parts of body surface Excretion of salt ions and small amounts of water in scanty urine from kidneys (b) Osmoregulation in a freshwater fish Gain of water and some ions in food Key Water Salt Uptake of salt ions by gills Osmotic water gain through gills and other parts of body surface Excretion of salt ions and large amounts of water in dilute urine from kidneys
Figure 44. 3 a (a) Osmoregulation in a marine fish Gain of water and salt ions from food Gain of water and salt ions from drinking seawater Excretion of salt ions from gills Osmotic water loss through gills and other parts of body surface Excretion of salt ions and small amounts of water in scanty urine from kidneys Key Water Salt
Freshwater Animals • Freshwater animals constantly take in water by osmosis 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 in foods and by uptake across the gills © 2011 Pearson Education, Inc.
Figure 44. 3 b (b) Osmoregulation in a freshwater fish Gain of water and some ions in food Key Water Salt Uptake of salt ions by gills Osmotic water gain through gills and other parts of body surface Excretion of salt ions and large amounts of water in dilute urine from kidneys
Figure 44. 4
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 © 2011 Pearson Education, Inc.
Figure 44. 5 50 m (a) Hydrated tardigrade (b) Dehydrated tardigrade
Figure 44. 5 a 50 m (a) Hydrated tardigrade
Figure 44. 5 b 50 m (b) Dehydrated tardigrade
Land Animals • Adaptations to reduce water loss are key to survival on land • Body coverings of most terrestrial animals help prevent dehydration • Desert animals get major water savings from simple anatomical features and behaviors such as a nocturnal lifestyle • Land animals maintain water balance by eating moist food and producing water metabolically through cellular respiration © 2011 Pearson Education, Inc.
Figure 44. 6 Water balance in a kangaroo rat (2 m. L/day) Ingested in food (0. 2) Water gain (m. L) Derived from metabolism (1. 8) Water balance in a human (2, 500 m. L/day) Ingested in food (750) Ingested in liquid (1, 500) Derived from metabolism (250) Feces (100) Feces (0. 09) Water loss (m. L) Urine (0. 45) Evaporation (1. 46) Urine (1, 500) Evaporation (900)
Energetics of Osmoregulation • Osmoregulators must expend energy to maintain osmotic gradients • The amount of energy differs based on – How different the animal’s osmolarity is from its surroundings – How easily water and solutes move across the animal’s surface – The work required to pump solutes across the membrane © 2011 Pearson Education, Inc.
Transport Epithelia in Osmoregulation • Animals regulate the solute content of body fluid that bathes their cells • Transport epithelia are epithelial cells that are specialized for moving solutes in specific directions • They are typically arranged in complex tubular networks • An example is in nasal glands of marine birds, which remove excess sodium chloride from the blood © 2011 Pearson Education, Inc.
Figure 44. 7 Secretory cell Lumen of of transport secretory Vein Artery epithelium tubule Nasal salt gland Ducts Nasal gland Nostril with salt secretions (a) Location of nasal glands in a marine bird Salt ions Capillary Secretory tubule Transport epithelium (b) Secretory tubules Blood flow Key Salt movement Blood flow Salt secretion (c) Countercurrent exchange Central duct
Figure 44. 7 a Nasal salt gland Ducts Nasal gland Nostril with salt secretions (a) Location of nasal glands in a marine bird
Figure 44. 7 b Vein Artery Nasal gland Capillary Secretory tubule Transport epithelium Key Salt movement Blood flow (b) Secretory tubules Central duct
Figure 44. 7 c Secretory cell Lumen of of transport secretory epithelium tubule Salt ions Blood flow Salt secretion (c) Countercurrent exchange
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 significant wastes are nitrogenous breakdown products of proteins and nucleic acids • Some animals convert toxic ammonia (NH 3) to less toxic compounds prior to excretion © 2011 Pearson Education, Inc.
Figure 44. 8 Proteins Nucleic acids Amino acids Nitrogenous bases —NH 2 Amino groups Most aquatic animals, including most bony fishes Ammonia Mammals, most amphibians, sharks, some bony fishes Urea Many reptiles (including birds), insects, land snails Uric acid
Figure 44. 8 a Most aquatic animals, including most bony fishes Ammonia Mammals, most amphibians, sharks, some bony fishes Urea Many reptiles (including birds), insects, land snails Uric acid
Forms of Nitrogenous Wastes • Animals excrete nitrogenous wastes in different forms: ammonia, urea, or uric acid • These differ in toxicity and the energy costs of producing them © 2011 Pearson Education, Inc.
Ammonia • Animals that excrete nitrogenous wastes as ammonia need access to lots of water • They release ammonia across the whole body surface or through gills © 2011 Pearson Education, Inc.
Urea • The liver of mammals and most adult amphibians converts ammonia to the less toxic urea • The circulatory system carries urea to the kidneys, where it is excreted • Conversion of ammonia to urea is energetically expensive; excretion of urea requires less water than ammonia © 2011 Pearson Education, Inc.
Uric Acid • Insects, land snails, and many reptiles, including birds, mainly excrete uric acid • Uric acid is relatively nontoxic and does not dissolve readily in water • It can be secreted as a paste with little water loss • Uric acid is more energetically expensive to produce than urea © 2011 Pearson Education, Inc.
Figure 44. 9
The Influence of Evolution and Environment on Nitrogenous Wastes • The kinds of nitrogenous wastes excreted depend on an animal’s evolutionary history and habitat, especially water availability • Another factor is the immediate environment of the animal egg • The amount of nitrogenous waste is coupled to the animal’s energy budget © 2011 Pearson Education, Inc.
Concept 44. 3: Diverse excretory systems are variations on a tubular theme • Excretory systems regulate solute movement between internal fluids and the external environment © 2011 Pearson Education, Inc.
Excretory Processes • Most excretory systems produce urine by refining a filtrate derived from body fluids • Key functions of most excretory systems – Filtration: Filtering of body fluids – Reabsorption: Reclaiming valuable solutes – Secretion: Adding nonessential solutes and wastes from the body fluids to the filtrate – Excretion: Processed filtrate containing nitrogenous wastes, released from the body © 2011 Pearson Education, Inc.
Figure 44. 10 1 Filtration Capillary Filtrate Excretory tubule 2 Reabsorption 3 Secretion Urine 4 Excretion
Survey of Excretory Systems • Systems that perform basic excretory functions vary widely among animal groups • They usually involve a complex network of tubules © 2011 Pearson Education, Inc.
Protonephridia • A protonephridium is a network of dead-end tubules connected to external 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 © 2011 Pearson Education, Inc.
Figure 44. 11 Nucleus of cap cell Flame bulb Tubules of protonephridia Cilia Interstitial fluid flow Opening in body wall Tubule cell
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 © 2011 Pearson Education, Inc.
Figure 44. 12 Coelom Components of a metanephridium: Collecting tubule Internal opening Bladder External opening Capillary network
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, mainly uric acid, an important adaptation to terrestrial life • Some terrestrial insects can also take up water from the air © 2011 Pearson Education, Inc.
Figure 44. 13 Digestive tract Rectum Hindgut Intestine Midgut Malpighian (stomach) tubules Salt, water, and Feces nitrogenous and urine wastes To anus Malpighian tubule Rectum Reabsorption HEMOLYMPH
Kidneys • Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation © 2011 Pearson Education, Inc.
Figure 44. 14 -a Excretory Organs Kidney Structure Posterior vena cava Renal cortex Renal medulla Cortical Juxtamedullary nephron Renal artery Kidney Renal artery and vein Renal vein Aorta Ureter Urinary bladder Nephron Types Renal cortex Ureter Urethra Renal medulla Renal pelvis
Figure 44. 14 -b Nephron Organization Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Distal tubule Efferent arteriole from glomerulus Collecting duct Descending limb Loop of Henle Vasa recta Ascending limb 200 m Branch of renal vein Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow.
Figure 44. 14 a Excretory Organs Posterior vena cava Renal artery and vein Kidney Aorta Ureter Urinary bladder Urethra
Figure 44. 14 b Kidney Structure Renal cortex Renal medulla Renal artery Renal vein Ureter Renal pelvis
Figure 44. 14 c Nephron Types Cortical nephron Renal cortex Renal medulla Juxtamedullary nephron
Figure 44. 14 d Nephron Organization Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Distal tubule Efferent arteriole from glomerulus Collecting duct Branch of renal vein Vasa recta Descending limb Loop of Henle Ascending limb
200 m Figure 44. 14 e Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow.
Concept 44. 4: The nephron is organized for stepwise processing of blood filtrate • The filtrate produced in Bowman’s capsule contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules © 2011 Pearson Education, Inc.
From Blood Filtrate to Urine: A Closer Look Proximal Tubule • Reabsorption of ions, water, and nutrients takes place in the proximal tubule • Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries • Some toxic materials are actively secreted into the filtrate • As the filtrate passes through the proximal tubule, materials to be excreted become concentrated Animation: Bowman’s Capsule and Proximal Tubule © 2011 Pearson Education, Inc.
Figure 44. 15 Proximal tubule Na. Cl Nutrients H 2 O HCO 3 K H Filtrate NH 3 Distal tubule H 2 O Na. Cl K HCO 3 H CORTEX Loop of Henle Na. Cl OUTER MEDULLA H 2 O Na. Cl Collecting duct Key Active transport Passive transport Urea Na. Cl INNER MEDULLA H 2 O
Descending Limb of the Loop of Henle • Reabsorption of water continues through channels formed by aquaporin proteins • Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate • The filtrate becomes increasingly concentrated © 2011 Pearson Education, Inc.
Ascending Limb of the Loop of Henle • In the ascending limb of the loop of Henle, salt but not water is able to diffuse from the tubule into the interstitial fluid • The filtrate becomes increasingly dilute © 2011 Pearson Education, Inc.
Distal Tubule • The distal tubule regulates the K+ and Na. Cl concentrations of body fluids • The controlled movement of ions contributes to p. H regulation Animation: Loop of Henle and Distal Tubule © 2011 Pearson Education, Inc.
Collecting Duct • The collecting duct carries filtrate through the medulla to the renal pelvis • One of the most important tasks is reabsorption of solutes and water • Urine is hyperosmotic to body fluids Animation: Collecting Duct © 2011 Pearson Education, Inc.
Solute Gradients and Water Conservation • The mammalian kidney’s ability to conserve water is a key terrestrial adaptation • Hyperosmotic urine can be produced only because considerable energy is expended to transport solutes against concentration gradients • The two primary solutes affecting osmolarity are Na. Cl and urea © 2011 Pearson Education, Inc.
The Two-Solute Model • In the proximal tubule, filtrate volume decreases, but its osmolarity remains the same • The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney • This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient • Considerable energy is expended to maintain the osmotic gradient between the medulla and cortex © 2011 Pearson Education, Inc.
• 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 Na. Cl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood © 2011 Pearson Education, Inc.
Figure 44. 16 -1 Osmolarity of interstitial fluid (m. Osm/L) 300 300 CORTEX H 2 O 400 H 2 O OUTER MEDULLA H 2 O 600 900 H 2 O Key Active transport Passive transport INNER MEDULLA H 2 O 1, 200
Figure 44. 16 -2 Osmolarity of interstitial fluid (m. Osm/L) 300 100 CORTEX OUTER MEDULLA Na. Cl H 2 O 400 Na. Cl H 2 O Na. Cl 600 Active transport Passive transport INNER MEDULLA H 2 O 200 400 600 700 900 Na. Cl H 2 O Key Na. Cl H 2 O 300 900 Na. Cl 1, 200
Figure 44. 16 -3 Osmolarity of interstitial fluid (m. Osm/L) 300 100 CORTEX H 2 O 400 Na. Cl 300 400 H 2 O Na. Cl H 2 O 300 200 H 2 O Na. Cl OUTER MEDULLA H 2 O Na. Cl 600 400 600 H 2 O Na. Cl H 2 O Urea H 2 O Key Active transport Passive transport INNER MEDULLA H 2 O 900 Na. Cl 700 H 2 O Urea 1, 200 900 Urea 1, 200
Adaptations of the Vertebrate Kidney to Diverse Environments • The form and function of nephrons in various vertebrate classes are related to requirements for osmoregulation in the animal’s habitat © 2011 Pearson Education, Inc.
Mammals • The juxtamedullary nephron is key to water conservation in terrestrial animals • Mammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops © 2011 Pearson Education, Inc.
Birds and Other Reptiles • Birds have shorter loops of Henle but conserve water by excreting uric acid instead of urea • Other reptiles have only cortical nephrons but also excrete nitrogenous waste as uric acid © 2011 Pearson Education, Inc.
Figure 44. 17
Freshwater Fishes and Amphibians • Freshwater fishes conserve salt in their distal tubules and excrete large volumes of dilute urine • Kidney function in amphibians is similar to freshwater fishes • Amphibians conserve water on land by reabsorbing water from the urinary bladder © 2011 Pearson Education, Inc.
Marine Bony Fishes • Marine bony fishes are hypoosmotic compared with their environment • Their kidneys have small glomeruli and some lack glomeruli entirely • Filtration rates are low, and very little urine is excreted © 2011 Pearson Education, Inc.
Concept 44. 5: Hormonal circuits link kidney function, water balance, and blood pressure • Mammals control the volume and osmolarity of urine • The kidneys of the South American vampire bat can produce either very dilute or very concentrated urine • This allows the bats to reduce their body weight rapidly or digest large amounts of protein while conserving water © 2011 Pearson Education, Inc.
Figure 44. 18
Antidiuretic Hormone • The osmolarity of the urine is regulated by nervous and hormonal control • Antidiuretic hormone (ADH) makes the collecting duct epithelium more permeable to water • An increase in osmolarity triggers the release of ADH, which helps to conserve water Animation: Effect of ADH © 2011 Pearson Education, Inc.
Figure 44. 19 -1 Thirst Osmoreceptors in hypothalamus trigger release of ADH. Hypothalamus ADH Pituitary gland STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Homeostasis: Blood osmolarity (300 m. Osm/L)
Figure 44. 19 -2 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus Drinking reduces blood osmolarity to set point. ADH Increased permeability Distal tubule Pituitary gland STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) H 2 O reabsorption helps prevent further osmolarity increase. Collecting duct Homeostasis: Blood osmolarity (300 m. Osm/L)
• Binding of ADH to receptor molecules leads to a temporary increase in the number of aquaporin proteins in the membrane of collecting duct cells © 2011 Pearson Education, Inc.
Figure 44. 20 Collecting duct ADH receptor ADH LUMEN COLLECTING DUCT CELL c. AMP Second-messenger signaling molecule Storage vesicle Exocytosis Aquaporin water channel H 2 O
• Mutation in ADH production causes severe dehydration and results in diabetes insipidus • Alcohol is a diuretic as it inhibits the release of ADH © 2011 Pearson Education, Inc.
Figure 44. 21 EXPERIMENT 1 Prepare copies of human aquaporin genes: two mutants plus wild type. Aquaporin gene Promoter Mutant 2 Wild type Mutant 1 2 Synthesize m. RNA. H 2 O (control) 3 Inject m. RNA into frog oocytes. 4 Transfer to 10 -m. Osm solution and observe results. Aquaporin proteins RESULTS Injected RNA Permeability ( m/sec) Wild-type aquaporin 196 None 20 Aquaporin mutant 1 17 Aquaporin mutant 2 18
Figure 44. 21 a EXPERIMENT 1 Prepare copies of human aquaporin genes: two mutants plus wild type. Aquaporin gene Promoter Mutant 1 Mutant 2 Wild type 2 Synthesize m. RNA. H 2 O (control) 3 Inject m. RNA into frog oocytes. 4 Transfer to 10 -m. Osm solution and observe results. Aquaporin proteins
Figure 44. 21 b RESULTS Injected RNA Permeability ( m/sec) Wild-type aquaporin 196 None 20 Aquaporin mutant 1 17 Aquaporin mutant 2 18
The Renin-Angiotensin-Aldosterone System • The renin-angiotensin-aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis • A drop in blood pressure near the glomerulus causes the juxtaglomerular apparatus (JGA) to release the enzyme renin • Renin triggers the formation of the peptide angiotensin II © 2011 Pearson Education, Inc.
• Angiotensin II – Raises blood pressure and decreases blood flow to the kidneys – Stimulates the release of the hormone aldosterone, which increases blood volume and pressure © 2011 Pearson Education, Inc.
Figure 44. 22 -1 JGA releases renin. Distal tubule Renin Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Homeostasis: Blood pressure, volume
Figure 44. 22 -2 Liver Angiotensinogen JGA releases renin. Distal tubule Renin Angiotensin I ACE Angiotensin II Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Homeostasis: Blood pressure, volume
Figure 44. 22 -3 Liver Angiotensinogen JGA releases renin. Distal tubule Renin Angiotensin I ACE Angiotensin II Juxtaglomerular apparatus (JGA) Adrenal gland Aldosterone More Na and H 2 O are reabsorbed in distal tubules, increasing blood volume. Arterioles constrict, increasing blood pressure. STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Homeostasis: Blood pressure, volume
Homeostatic Regulation of the Kidney • ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume • Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS • ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin © 2011 Pearson Education, Inc.
Figure 44. UN 01 Animal Freshwater fish. Lives in water less concentrated than body fluids; fish tends to gain water, lose salt Inflow/Outflow Does not drink water Salt in H 2 O in (active transport by gills) Urine Large volume of urine Urine is less concentrated than body fluids Salt out Marine bony fish. Lives in water more concentrated than body fluids; fish tends to lose water, gain salt Drinks water Salt in H 2 O out Small volume of urine Urine is slightly less concentrated than body fluids Salt out (active transport by gills) Terrestrial vertebrate. Terrestrial environment; tends to lose body water to air Drinks water Salt in (by mouth) H 2 O and salt out Moderate volume of urine Urine is more concentrated than body fluids
Figure 44. UN 01 a Animal Inflow/Outflow Freshwater fish. Lives in water less concentrated than body fluids; fish tends to gain water, lose salt Does not drink water H 2 O in Salt in (active transport by gills) Salt out Urine Large volume of urine Urine is less concentrated than body fluids
Figure 44. UN 01 b Animal Inflow/Outflow Marine bony fish. Lives in water more concentrated than body fluids; fish tends to lose water, gain salt Drinks water Salt in H 2 O out Urine Small volume of urine Urine is slightly less concentrated than body fluids Salt out (active transport by gills)
Figure 44. UN 01 c Animal Terrestrial vertebrate. Terrestrial environment; tends to lose body water to air Inflow/Outflow Drinks water Salt in (by mouth) H 2 O and salt out Urine Moderate volume of urine Urine is more concentrated than body fluids
Figure 44. UN 02
- Slides: 95