Fig. 44-1 Osmoregulation and Excretion Chapter 44 Osmoregulation is based largely on controlled...
-
Upload
nathaniel-pitts -
Category
Documents
-
view
216 -
download
0
Transcript of Fig. 44-1 Osmoregulation and Excretion Chapter 44 Osmoregulation is based largely on controlled...
Fig. 44-1
Osmoregulation and Excretion
Chapter 44
Osmoregulationis based largely on controlled movement of solutes between internal fluids and the external environment
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
• Most animals are stenohaline; they cannot tolerate substantial changes in external osmolarity
• Euryhaline animals can survive large fluctuations in external osmolarity
Fig. 44-4
Excretionof salt ionsfrom gills
Gain of water andsalt ions from food
Osmotic waterloss through gillsand other partsof body surface
Uptake of water andsome ions in food
Uptakeof salt ionsby gills
Osmotic watergain through gillsand other partsof body surface
Excretion of largeamounts of water indilute urine from kidneys
Excretion of salt ions andsmall amounts of water inscanty urine from kidneys
Gain of waterand salt ions fromdrinking seawater
(a) Osmoregulation in a saltwater fish (b) Osmoregulation in a freshwater fish
Fig. 44-5
(a) Hydrated tardigrade (b) Dehydrated tardigrade
100 µm
100 µmanhydrobiosis
Fig. 44-6
Watergain(mL)
Waterloss(mL)
Urine(0.45)
Urine(1,500)
Evaporation (1.46) Evaporation (900)
Feces (0.09) Feces (100)
Derived frommetabolism (1.8)
Derived frommetabolism (250)
Ingestedin food (750)
Ingestedin food (0.2)
Ingestedin liquid (1,500)
Waterbalance in akangaroo rat(2 mL/day)
Waterbalance ina human(2,500 mL/day)
Land Animals
Transport Epithelia in Osmoregulation
• Animals regulate the composition of body fluid that bathes their cells
• Transport epithelia are specialized epithelial 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
Fig. 44-7
Ducts
Nostrilwith saltsecretions
Nasal saltgland
EXPERIMENT
Fig. 44-8
Salt gland
Secretorycell
Capillary
Secretory tubule
Transportepithelium
Direction ofsalt movement
Central duct
(a)
Bloodflow
(b)
Secretorytubule
ArteryVein
NaCl
NaCl
Salt secretion
Countercurrent exchange
• 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
• Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion
Fig. 44-9
Many reptiles(including birds),insects, land snails
Ammonia Uric acidUrea
Most aquaticanimals, includingmost bony fishes
Mammals, mostamphibians, sharks,some bony fishes
Nitrogenous bases
Amino acids
Proteins Nucleic acids
Amino groups
Concept 44.2: An animal’s
nitrogenous wastes reflect its phylogeny and habitat
Fig. 44-10
Capillary
Secretion adding toxins and other solutes from the body fluids to the filtrate
Reabsorption
Excretorytubule
Filtration: pressure-filtering of body fluids
Filtrate
Urin
e
reclaiming valuable solutes
Excretion removing the filtrate from the system
Key functions of most excretory systems:
Fig. 44-11
Tubule
Tubules ofprotonephridia
Cilia
Interstitialfluid flow
Opening inbody wall
Nucleusof cap cell
Flamebulb
Tubule cell
Fig. 44-12
Capillarynetwork
Components ofa metanephridium:
External opening
Coelom
Collecting tubule
Internal opening
Bladder
Fig. 44-13
Rectum
Digestive tract
HindgutIntestine
Malpighiantubules
Rectum
Feces and urine
HEMOLYMPH
Reabsorption
Midgut(stomach)
Salt, water, and nitrogenous
wastes
Structure of the Mammalian Excretory System
• 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, and urine is expelled through a urethra
Fig. 44-14
Posteriorvena cava
Renal arteryand vein
Urinarybladder
Ureter
Aorta
Urethra
Kidney
(a) Excretory organs and major
associated blood vessels Cortical
nephronJuxtamedullarynephron
Collectingduct
(c) Nephron types
Torenalpelvis
Renalmedulla
Renalcortex
10 µm
Afferent arteriolefrom renal artery
Efferentarteriole fromglomerulus
SEM
Branch ofrenal vein
Descendinglimb
Ascendinglimb
Loop ofHenle
(d) Filtrate and blood flow
Vasarecta
Collectingduct
Distaltubule
Peritubular capillariesProximal tubule
Bowman’s capsule
Glomerulus
Ureter
Renal medulla
Renal cortex
Renal pelvis
(b) Kidney structure Section of kidneyfrom a rat 4 mm
Fig. 44-14b
(b) Kidney structureSection of kidneyfrom a rat 4 mm
Renalcortex
Renalmedulla
Renalpelvis
Ureter
Fig. 44-14cd
Corticalnephron
Juxtamedullarynephron
Collectingduct
(c) Nephron types
Torenalpelvis
Renalmedulla
Renalcortex
10 µm
Afferent arteriolefrom renal artery
Efferentarteriole fromglomerulus
SEM
Branch ofrenal vein
Descendinglimb
Ascendinglimb
Loop ofHenle
(d) Filtrate and blood flow
Vasarecta
Collectingduct
Distaltubule
Peritubular capillaries
Proximal tubuleBowman’s capsule
Glomerulus
• The nephron, the functional unit of the vertebrate kidney, consists of a single long tubule and a ball of capillaries called the glomerulus
• Bowman’s capsule surrounds and receives filtrate from the glomerulus
Fig. 44-14cCorticalnephron
Juxtamedullarynephron
Collectingduct
(c) Nephron types
Torenalpelvis
Renalmedulla
Renalcortex
Fig. 44-14dAfferent arteriolefrom renal artery
Efferentarteriole fromglomerulus
SEM
Branch ofrenal vein
Descendinglimb
Ascendinglimb
Loop ofHenle
(d) Filtrate and blood flow
Vasarecta
Collectingduct
Distaltubule
Peritubular capillaries
Proximal tubule
Bowman’s capsuleGlomerulus
10 µm
Filtration of the Blood
• Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule
• Filtration of small molecules is nonselective
• The filtrate contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
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, all of which lead to the renal pelvis, which is drained by the ureter
• Cortical nephrons are confined to the renal cortex, while juxtamedullary nephrons have loops of Henle that descend into the renal medulla
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
• Vasa recta are capillaries that serve the loop of Henle
• The vasa recta and the loop of Henle function as a countercurrent system
Concept 44.4: The nephron is organized for stepwise processing of blood filtrate
• The mammalian kidney conserves water by producing urine that is much more concentrated than body fluids
Fig. 44-15
Key
ActivetransportPassivetransport
INNERMEDULLA
OUTERMEDULLA
H2O
CORTEX
Filtrate
Loop ofHenle
H2O K+HCO3–
H+ NH3
Proximal tubule
NaCl Nutrients
Distal tubule
K+ H+
HCO3–
H2O
H2O
NaCl
NaCl
NaCl
NaCl
Urea
Collectingduct
NaCl
H2O
Salts
HCO3-
H+
Urea
Glucose
Amino acid
Some drugs
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 secreted into the filtrate
• The filtrate volume decreases
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
Ascending Limb of the Loop of Henlesalt but not water is able to diffuse from the tubule into the interstitial fluid, The filtrate becomes increasingly dilute
The thin segment: NaCl diffuses out to help maintain the osmolarity of the interstitial fluidThe thick segment: actively transports NaCl into the interstitial fluid
Distal Tubule
The distal tubule regulates the K+ and NaCl concentrations of body fluidsThe controlled movement of ions contributes to pH regulation
Collecting Duct
The collecting duct carries filtrate through the medulla to the renal pelvisWater is lost as well as some salt and urea, and the filtrate becomes more concentratedUrine is hyperosmotic to body fluids
Solute Gradients and Water Conservation
• Urine is much more concentrated than blood
– The osmolarity of blood is about 300 mOsm/L
– Urine: 1,200mOsm/L, Australian hopping mice:9,300mOsm/L
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 (the loop of Henle) and urea (the collecting duct) contribute to the osmolarity of the interstitial fluid, which causes reabsorption of water in the kidney and concentrates the urine
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Fig. 42-22
Anatomy of gills
Gillarch
Waterflow Operculum
Gillarch
Gill filamentorganization
Bloodvessels
Oxygen-poor blood
Oxygen-rich blood
Fluid flowthrough
gill filament
Lamella
Blood flow throughcapillaries in lamella
Water flowbetweenlamellae
Countercurrent exchangePO2
(mm Hg) in water
PO2 (mm Hg) in blood
Net diffu-sion of O2
from waterto blood
150 120 90 60 30
110 80 20Gill filaments
50140
To maximize oxygen absorption by fish gills
The countercurrent mechanisms involve passive movement
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings Fig. 40-12
Canada goose Bottlenosedolphin
Artery
Artery
Vein Vein
Blood flow
33º35ºC
27º30º
18º20º
10º 9º To reduce heat loss in endotherms
The countercurrent mechanisms involve passive movement
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
countercurrent multiplier systems
• The countercurrent system involvig the loop of Henle expends energy to actively transport NaCl from the filtrate in the upper part of the ascending limb of the loop.
• To expend energy to create concentration gradients, are called countercurrent multiplier systems.
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
– Considerable energy is expended to maintain the osmotic gradient between the medulla and cortex
• This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient
– Descending vessel conveys blood toward the inner medulla: water lost and NaCl isgained by diffusion.
– Ascending vessel: these fluxess are reversed
• 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
Fig. 44-16-1
Key
Activetransport
Passivetransport
INNERMEDULLA
OUTERMEDULLA
CORTEXH2O
300300
300
H2O
H2O
H2O
400
600
900
H2O
H2O
1,200
H2O
300
Osmolarity ofinterstitial
fluid(mOsm/L)
400
600
900
1,200
Fig. 44-16-2
Key
Activetransport
Passivetransport
INNERMEDULLA
OUTERMEDULLA
CORTEXH2O
300300
300
H2O
H2O
H2O
400
600
900
H2O
H2O
1,200
H2O
300
Osmolarity ofinterstitial
fluid(mOsm/L)
400
600
900
1,200
100
NaCl
100
NaCl
NaCl
NaCl
NaCl
NaCl
NaCl
200
400
700
Fig. 44-16-3
Key
Activetransport
Passivetransport
INNERMEDULLA
OUTERMEDULLA
CORTEXH2O
300300
300
H2O
H2O
H2O
400
600
900
H2O
H2O
1,200
H2O
300
Osmolarity ofinterstitial
fluid(mOsm/L)
400
600
900
1,200
100
NaCl
100
NaCl
NaCl
NaCl
NaCl
NaCl
NaCl
200
400
700
1,200
300
400
600
H2O
H2O
H2O
H2O
H2O
H2O
H2O
NaCl
NaCl
Urea
Urea
Urea
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
The juxtamedullary nephron contributes to water conservation in terrestrial animalsMammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops
Mammals
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
Antidiuretic Hormone (vasopressin)
• 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
• An increase in osmolarity ADHincrease in the number of aquaporin molecules in the membranes of collecting duct cells.
• Diabetes insipidus
Fig. 44-19
Thirst
Drinking reducesblood osmolarity
to set point.
Osmoreceptors in hypothalamus trigger
release of ADH.
Increasedpermeability
Pituitarygland
ADH
Hypothalamus
Distaltubule
H2O reab-sorption helpsprevent further
osmolarityincrease.
STIMULUS:Increase in blood
osmolarity
Collecting duct
Homeostasis:Blood osmolarity
(300 mOsm/L)
(a)
Exocytosis
(b)
Aquaporinwaterchannels
H2O
H2O
Storagevesicle
Second messengersignaling molecule
cAMP
INTERSTITIALFLUID
ADHreceptor
ADH
COLLECTINGDUCTLUMEN
COLLECTINGDUCT CELL
Fig. 44-19a-1
Thirst
Osmoreceptors inhypothalamus trigger
release of ADH.
Pituitarygland
ADH
Hypothalamus
STIMULUS:Increase in blood
osmolarity
Homeostasis:Blood osmolarity
(300 mOsm/L)
(a)
Fig. 44-19a-2
Thirst
Drinking reducesblood osmolarity
to set point.
Increasedpermeability
Pituitarygland
ADH
Hypothalamus
Distaltubule
H2O reab-sorption helpsprevent further
osmolarityincrease.
STIMULUS:Increase in blood
osmolarity
Collecting duct
Homeostasis:Blood osmolarity
(300 mOsm/L)
(a)
Osmoreceptors inhypothalamus trigger
release of ADH.
Fig. 44-19b
Exocytosis
(b)
Aquaporinwaterchannels
H2O
H2O
Storagevesicle
Second messengersignaling molecule
cAMP
INTERSTITIALFLUID
ADHreceptor
ADH
COLLECTINGDUCTLUMEN
COLLECTINGDUCT CELL
1.Mutation in ADH production causes severe dehydration and results in diabetes insipidus
2.Alcohol is a diuretic as it inhibits the release of ADH
Fig. 44-20
Prepare copiesof human aqua-porin genes.
196
Transfer to10 mOsmsolution.
SynthesizeRNAtranscripts.
EXPERIMENT
Mutant 1 Mutant 2
Aquaporingene
Promoter
Wild type
H2O(control)
Inject RNAinto frogoocytes.
Aquaporinprotein
RESULTS
20
17
18
Permeability (µm/s)Injected RNA
Wild-type aquaporin
None
Aquaporin mutant 1
Aquaporin mutant 2
Fig. 44-20a
Prepare copiesof human aqua-porin genes.
Transfer to10 mOsmsolution.
SynthesizeRNAtranscripts.
EXPERIMENT
Mutant 1 Mutant 2 Wild type
H2O(control)
Inject RNAinto frogoocytes.
Aquaporinprotein
Promoter
Aquaporingene
Fig. 44-20b
196
RESULTS
20
17
18
Permeability (µm/s)Injected RNA
Wild-type aquaporin
None
Aquaporin mutant 1
Aquaporin mutant 2
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
• 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
Fig. 44-21-1
Renin
Distaltubule
Juxtaglomerularapparatus (JGA)
STIMULUS:Low blood volumeor blood pressure
Homeostasis:Blood pressure,
volume
Fig. 44-21-2
Renin
Distaltubule
Juxtaglomerularapparatus (JGA)
STIMULUS:Low blood volumeor blood pressure
Homeostasis:Blood pressure,
volume
Liver
Angiotensinogen
Angiotensin I
ACE
Angiotensin II
Fig. 44-21-3
Renin
Distaltubule
Juxtaglomerularapparatus (JGA)
STIMULUS:Low blood volumeor blood pressure(due to dehydration or blood loss)
Homeostasis:Blood pressure,
volume
Liver
Angiotensinogen
Angiotensin I
ACE
Angiotensin II
Adrenal gland
Aldosterone
ArterioleconstrictionIncreased Na+
and H2O reabsorption indistal tubules
Angiotensin converting enzyme
Homeostatic Regulation of the Kidney
• ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume
– A situation that causes an excessive loss of both salt and body fluids—a major wound, for example, or severe diarrhea will reduce blood volume without increasing osmolarity. This will not affect ADH release, but the RAAS will respond to the drop in blood volume and pressure by increasing water and Na+ reabsorption.
• Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS
ANP– ANP is released in response to an increase in blood
volume and pressure and the release of renin
– ANP( the wall of the atria of the heart)--> inhibits renin from the JGA Inhibits NaCl reabsorption by the collecting ducts and reduces aldosterone release from the adrenal glands lower blood volume and pressure
– Thus, ADH, the RASS, and ANP are provided to control the osmolarity, salt concentration, volume, and pressure of blood
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
• Conn’s syndrome?
• A tumor in the adrenal cortex high amounts of aldosterone
– The major symptom?