chapter42 circulation and gas exchange
TRANSCRIPT
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PowerPoint Lectures forBio logy, Seventh Edi t ion
Neil Campbell and Jane Reece
Lectures by Chris Romero
Chapter 42
Circulation and Gas
ExchangeMATERIALS FOR
BIOLOGY OLYMPIAD PREPARATIONDWIWARNA HIGH BOARDING SCHOOL BOGOR
INSTRUCTOR:WIDIATI and SUGANDA KUSMANA
CORRESPONDENCE:[email protected]
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Overview: Trading with the Environment
Every organism must exchange materials withits environment
And this exchange ultimately occurs at thecellular level
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In unicellular organisms
These exchanges occur directly with theenvironment
For most of the cells making up multicellularorganisms
Direct exchange with the environment is notpossible
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The feathery gills projecting from a salmon
Are an example of a specialized exchangesystem found in animals
Figure 42.1
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Concept 42.1: Circulatory systems reflect
phylogeny Transport systems
Functionally connect the organs of exchangewith the body cells
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Most complex animals have internal transport
systems That circulate fluid, providing a lifeline between
the aqueous environment of living cells and theexchange organs, such as lungs, that exchangechemicals with the outside environment
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Invertebrate Circulation
The wide range of invertebrate body size and
form Is paralleled by a great diversity in circulatory
systems
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Gastrovascular Cavities
Simple animals, such as cnidarians
Have a body wall only two cells thick thatencloses a gastrovascular cavity
The gastrovascular cavity
Functions in both digestion and distribution ofsubstances throughout the body
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Some cnidarians, such as jellies
Have elaborate gastrovascular cavities
Figure 42.2
Circularcanal
Radial canal
5 cmMouth
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Open and Closed Circul atory Systems
More complex animals
Have one of two types of circulatory systems:open or closed
Both of these types of systems have threebasic components
A circulatory fluid (blood)
A set of tubes (blood vessels) A muscular pump (the heart)
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In insects, other arthropods, and most molluscs
Blood bathes the organs directly in an opencirculatory system
Heart
Hemolymph in sinusessurrounding ograns
Anteriorvessel
Tubular heart
Lateral
vessels
Ostia
(a) An open circulatory systemFigure 42.3a
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In a closed circulatory system
Blood is confined to vessels and is distinctfrom the interstitial fluid
Figure 42.3b
Interstitialfluid
Heart
Small branch vesselsin each organ
Dorsal vessel(main heart)
Ventral vessels Auxiliary hearts
(b) A closed circulatory system
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Closed systems
Are more efficient at transporting circulatoryfluids to tissues and cells
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Survey of Vertebrate Circulation
Humans and other vertebrates have a closed
circulatory system Often called the cardiovascular system
Blood flows in a closed cardiovascular system
Consisting of blood vessels and a two- to four-chambered heart
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Arteries carry blood to capillaries
The sites of chemical exchange between theblood and interstitial fluid
Veins
Return blood from capillaries to the heart
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Fishes
A fish heart has two main chambers
One ventricle and one atrium
Blood pumped from the ventricle
Travels to the gills, where it picks up O 2 anddisposes of CO 2
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Amphibians
Frogs and other amphibians
Have a three-chambered heart, with two atriaand one ventricle
The ventricle pumps blood into a forked artery
That splits the ventricles output into thepulmocutaneous circuit and the systemiccircuit
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Reptiles (Except Birds)
Reptiles have double circulation
With a pulmonary circuit (lungs) and asystemic circuit
Turtles, snakes, and lizards
Have a three-chambered heart
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M ammals and Birds
In all mammals and birds
The ventricle is completely divided intoseparate right and left chambers
The left side of the heart pumps and receivesonly oxygen-rich blood While the right side receives and pumps only
oxygen-poor blood
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A powerful four-chambered heart
Was an essential adaptation of theendothermic way of life characteristic ofmammals and birds
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FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS
Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries
Lung capillaries Lung capillariesLung and skin capillariesGill capillaries
Right Left Right Left Right LeftSystemic
circuitSystemic
circuit
Pulmocutaneouscircuit
Pulmonarycircuit
Pulmonarycircuit
SystemiccirculationVein
Atrium (A)
Heart:ventricle (V)
Artery Gillcirculation
A
V VV VV
A A A A ALeftSystemic
aorta
Rightsystemicaorta
Figure 42.4
Vertebrate circulatory systems
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Concept 42.2: Double circulation in mammalsdepends on the anatomy and pumping cycle ofthe heart
The structure and function of the human
circulatory system Can serve as a model for exploring
mammalian circulation in general
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Mammalian Circulation: The Pathway
Heart valves
Dictate a one-way flow of blood through theheart
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Blood begins its flow
With the right ventricle pumping blood to thelungs
In the lungs
The blood loads O 2 and unloads CO 2
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The mammalian cardiovascular system
Pulmonaryvein
Right atrium
Right ventricle
Posteriorvena cava Capillaries of
abdominal organsand hind limbs
Aorta
Left ventricle
Left atriumPulmonaryvein
Pulmonaryartery
Capillariesof left lung
Capillaries ofhead andforelimbs
Anteriorvena cava
Pulmonaryartery
Capillariesof right lung
Aorta
Figure 42.5
1
10
11
5
4
6
2
9
3 3
7
8
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The Mammalian Heart: A Closer Look
A closer look at the mammalian heart
Provides a better understanding of how doublecirculation works
Figure 42.6
Aorta
Pulmonaryveins
Semilunarvalve
Atrioventricularvalve
Left ventricleRight ventricle
Anterior vena cava
Pulmonary artery
Semilunarvalve
Atrioventricularvalve
Posteriorvena cava
Pulmonaryveins
Right atrium
Pulmonary
artery
Leftatrium
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The heart contracts and relaxes
In a rhythmic cycle called the cardiac cycle
The contraction, or pumping, phase of thecycle
Is called systole
The relaxation, or filling, phase of the cycle
Is called diastole
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The cardiac cycle
Figure 42.7
Semilunar
valvesclosed
AV valvesopen
AV valvesclosed
Semilunarvalvesopen
Atrial andventriculardiastole
1
Atrial systole;
ventriculardiastole
2
Ventricular systole;atrial diastole
3
0.1 sec
0.3 sec0.4 sec
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The heart rate, also called the pulse
Is the number of beats per minute
The cardiac output
Is the volume of blood pumped into thesystemic circulation per minute
h h h
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Maintaining the Hearts Rhythmic Beat
Some cardiac muscle cells are self-excitable
Meaning they contract without any signal fromthe nervous system
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A region of the heart called the sinoatrial (SA)node, or pacemaker
Sets the rate and timing at which all cardiacmuscle cells contract
Impulses from the SA node Travel to the atrioventricular (AV) node
At the AV node, the impulses are delayed And then travel to the Purkinje fibers that make
the ventricles contract
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The impulses that travel during the cardiaccycle
Can be recorded as an electrocardiogram(ECG or EKG)
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The control of heart rhythm
Figure 42.8
SA node(pacemaker)
AV node Bundle
branchesHeartapex
Purkinjefibers
2 Signals are delayedat AV node.1 Pacemaker generateswave of signalsto contract.
3 Signals passto heart apex. 4 Signals spreadThroughoutventricles.
ECG
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The pacemaker is influenced by
Nerves, hormones, body temperature, andexercise
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Concept 42.3: Physical principles govern bloodcirculation
The same physical principles that govern themovement of water in plumbing systems
Also influence the functioning of animalcirculatory systems
Bl d V l St t d F ti
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Blood Vessel Structure and Function
The infrastructure of the circulatory system
Is its network of blood vessels
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All blood vessels
Are built of similar tissues Have three similar layers
Figure 42.9
Artery Vein
100 m
Artery Vein
ArterioleVenule
Connectivetissue
Smoothmuscle
Endothelium
Connectivetissue
Smoothmuscle
EndotheliumValve
Endothelium
Basementmembrane
Capillary
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Structural differences in arteries, veins, andcapillaries
Correlate with their different functions
Arteries have thicker walls
To accommodate the high pressure of bloodpumped from the heart
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In the thinner-walled veins
Blood flows back to the heart mainly as aresult of muscle action
Figure 42.10
Direction of blood flowin vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
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The velocity of blood flow varies in the circulatorysystem and is slowest in the capillary beds as aresult of the high resistance and large total cross-sectional area 5,000
4,0003,0002,0001,000
0
A o r t a
A r t e r i e s
A r t e r i o
l e s
C a p
i l l a r i e s
V e n u
l e s
V e
i n s
V e n a e c a v a e P
r e s s u r e
( m m
H g )
V e
l o c i
t y ( c m
/ s e c )
A r e a
( c m
2 )
Systolicpressure
Diastolicpressure
5040302010
0
120100
80604020
0
Blood Pressure
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Blood Pressure
Blood pressure
Is the hydrostatic pressure that blood exertsagainst the wall of a vessel
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Systolic pressure
Is the pressure in the arteries duringventricular systole
Is the highest pressure in the arteries
Diastolic pressure
Is the pressure in the arteries during diastole
Is lower than systolic pressure
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Blood pressure
Can be easily measured in humans
Figure 42.12
Artery
Rubber cuffinflatedwith air
Arteryclosed
120 120
Pressurein cuffabove 120
Pressurein cuffbelow 120
Pressurein cuffbelow 70
Soundsaudible instethoscope
Soundsstop
Blood pressurereading: 120/70
A typical blood pressure reading for a 20-year-oldis 120/70. The units for these numbers are mm ofmercury (Hg); a blood pressure of 120 is a force thatcan support a column of mercury 120 mm high.
1
A sphygmomanometer, an inflatable cuff attached to apressure gauge, measures blood pressure in an artery.The cuff is wrapped around the upper arm and inflateduntil the pressure closes the artery, so that no bloodflows past the cuff. When this occurs, the pressureexerted by the cuff exceeds the pressure in the artery.
2 A stethoscope is used to listen for sounds of blood flowbelow the cuff. If the artery is closed, there i s no pulsebelow the cuff. The cuff is gradually deflated until bloodbegins to flow into the forearm, and sounds from bloodpulsing into the artery below the cuff can be heard withthe stethoscope. This occurs when the blood pressureis greater than the pressure exerted by the cuff. Thepressure at this point is the systolic pressure.
3
The cuff is loosened further until the blood flows freelythrough the artery and the sounds below the cuff
disappear. The pressure at this point is the diastolicpressure remaining in the artery when the heart is relaxed.
4
70
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Blood pressure is determined partly by cardiacoutput
And partly by peripheral resistance due tovariable constriction of the arterioles
Capillary Function
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Capillary Function
Capillaries in major organs are usually filled tocapacity
But in many other sites, the blood supplyvaries
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Two mechanisms
Regulate the distribution of blood in capillarybeds
In one mechanism
Contraction of the smooth muscle layer in thewall of an arteriole constricts the vessel
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In a second mechanism
Precapillary sphincters control the flow ofblood between arterioles and venules
Figure 42.13 a
c
Precapillary sphincters Thoroughfarechannel
ArterioleCapillaries
Venule(a) Sphincters relaxed
(b) Sphincters contracted
Venule Arteriole
(c) Capillaries and larger vessels (SEM)
20 m
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The critical exchange of substances betweenthe blood and interstitial fluid
Takes place across the thin endothelial wallsof the capillaries
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The difference between blood pressure andosmotic pressure
Drives fluids out of capillaries at the arterioleend and into capillaries at the venule end
At the arterial end of a
capillary, blood pressure isgreater than osmotic pressure,and fluid flows out of the
capillary into the interstitial fluid.
Capillary Redbloodcell
15 m
Tissue cell INTERSTITIAL FLUID
CapillaryNet fluidmovement out
Net fluidmovement in
Direction of
blood flow
Blood pressureOsmotic pressure
Inward flow
Outward flow P r e s s u r e
Arterial end of capillary Venule end
At the venule end of a capillary,blood pressure is less thanosmotic pressure, and fluid flows
from the interstitial fluid into thecapillary.
Figure 42.14
Fluid Return by the Lymphatic System
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Fluid Return by the Lymphatic System
The lymphatic system
Returns fluid to the body from the capillarybeds
Aids in body defense
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Fluid reenters the circulation
Directly at the venous end of the capillary bedand indirectly through the lymphatic system
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Concept 42.4: Blood is a connective tissue withcells suspended in plasma
Blood in the circulatory systems of vertebrates
Is a specialized connective tissue
Blood Composition and Function
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Blood Composition and Function
Blood consists of several kinds of cells
Suspended in a liquid matrix called plasma
The cellular elements
Occupy about 45% of the volume of blood
Plasma
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Plasma
Blood plasma is about 90% water
Among its many solutes are Inorganic salts in the form of dissolved ions,
sometimes referred to as electrolytes
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The composition of mammalian plasmaPlasma 55%
Constituent Major functions
Water Solvent forcarrying othersubstances
SodiumPotassium
CalciumMagnesiumChlorideBicarbonate
Osmotic balancepH buffering, andregulation ofmembranepermeability
Albumin
Fibringen
Immunoglobulins(antibodies)
Plasma proteins
Icons (blood electrolytes
Osmotic balance,pH buffering
Substances transported by bloodNutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O 2 and CO 2)Hormones
Defense
Figure 42.15
Separatedbloodelements
Clotting
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Another important class of solutes is theplasma proteins
Which influence blood pH, osmotic pressure,and viscosity
Various types of plasma proteins Function in lipid transport, immunity, and blood
clotting
Cellul ar Elements
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Suspended in blood plasma are two classes ofcells
Red blood cells, which transport oxygen
White blood cells, which function in defense
A third cellular element, platelets
Are fragments of cells that are involved in
clotting
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Figure 42.15
Cellular elements 45%Cell type Number
per L (mm 3) of blood Functions
Erythrocytes(red blood cells) 5 6 million Transport oxygen
and help transportcarbon dioxide
Leukocytes(white blood cells)
5,000 10,000 Defense andimmunity
Eosinophil
Basophil
Platelets
NeutrophilMonocyte
Lymphocyte
250,000 400,000
Blood clotting
The cellular elements of mammalian blood
Separatedbloodelements
Erythrocytes
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y y
Red blood cells, or erythrocytes
Are by far the most numerous blood cells Transport oxygen throughout the body
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Platelets
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Platelets function in blood clotting
Stem Cells and the Replacement of Cellular Elements
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The cellular elements of blood wear out
And are replaced constantly throughout apersons life
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Erythrocytes, leukocytes, and platelets alldevelop from a common source
A single population of cells called pluripotentstem cells in the red marrow of bones
B cells T cells
Lymphoidstem cells
Pluripotent stem cells (in bone marrow)
Myeloidstem cells
Erythrocytes
Platelets Monocytes
Neutrophils
Eosinophils
Basophils
Lymphocytes
Figure 42.16
Blood Clotting
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When the endothelium of a blood vessel isdamaged
The clotting mechanism begins
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A cascade of complex reactions
Converts fibrinogen to fibrin, forming a clot
Plateletplug
Collagen fibers
Platelet releases chemicalsthat make nearby platelets sticky
Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)
Prothrombin Thrombin
Fibrinogen Fibrin5 m
Fibrin clot Red blood cell
The clotting process beginswhen the endothelium of avessel is damaged, exposingconnective tissue in thevessel wall to blood. Plateletsadhere to collagen fibers inthe connective tissue andrelease a substance thatmakes nearby platelets sticky.
1 The platelets form aplug that providesemergency protectionagainst blood loss.
2 This seal is reinforced by a clot of fibrin whenvessel damage is severe. Fibrin is formed via amultistep process: Clotting factors released fromthe clumped platelets or damaged cells mix withclotting factors in the plasma, forming anactivation cascade that converts a plasma proteincalled prothrombin to its active form, thrombin.Thrombin itself is an enzyme that catalyzes thefinal step of the clotting process, the conversion offibrinogen to fibrin. The threads of fibrin becomeinterwoven into a patch (see colorized SEM).
3
Figure 42.17
Cardiovascular Disease
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Cardiovascular diseases
Are disorders of the heart and the bloodvessels
Account for more than half the deaths in the
United States
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One type of cardiovascular disease,atherosclerosis Is caused by the buildup of cholesterol within arteries
Figure 42.18a, b
(a) Normal artery (b) Partly clogged artery50 m 250 m
Smooth muscleConnectivetissue Endothelium Plaque
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Hypertension, or high blood pressure
Promotes atherosclerosis and increases therisk of heart attack and stroke
A heart attack
Is the death of cardiac muscle tissue resultingfrom blockage of one or more coronary arteries
A stroke
Is the death of nervous tissue in the brain,usually resulting from rupture or blockage ofarteries in the head
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Concept 42.5: Gas exchange occurs acrossspecialized respiratory surfaces
Gas exchange
Supplies oxygen for cellular respiration anddisposes of carbon dioxide
Figure 42.19
Organismallevel
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO 2
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Animals require large, moist respiratorysurfaces for the adequate diffusion ofrespiratory gases
Between their cells and the respiratorymedium, either air or water
Gills in Aquatic Animals
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Gills are outfoldings of the body surface
Specialized for gas exchange
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In some invertebrates
The gills have a simple shape and aredistributed over much of the body
(a) Sea star. The gills of a seastar are simple tubularprojections of the skin.The hollow core of each gillis an extension of the coelom
(body cavity). Gas exchangeoccurs by diffusion across thegill surfaces, and fluid in thecoelom circulates in and out ofthe gills, aiding gas transport.The surfaces of a sea starstube feet also function ingas exchange.
Gills
Tube foot
Coelom
Figure 42.20a
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Many segmented worms have flaplike gills
That extend from each segment of their body
Figure 42.20b
(b) Marine worm. Manypolychaetes (marineworms of the phylum
Annelida) have a pairof flattened appendagescalled parapodia oneach body segment. Theparapodia serve as gillsand also function in
crawling and swimming.
Gill
Parapodia
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The gills of clams, crayfish, and many otheranimals
Are restricted to a local body region
Figure 42.20c, d
(d) Crayfish. Crayfish andother crustaceanshave long, featherygills covered by the
exoskeleton. Specializedbody appendagesdrive water overthe gill surfaces.
(c) Scallop. The gills of ascallop are long,flattened platesthat project from the
main body massinside the hard shell.Cilia on the gillscirculate water aroundthe gill surfaces.
Gills
Gills
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The effectiveness of gas exchange in somegills, including those of fishes
Is increased by ventilation and countercurrentflow of blood and water
Countercurrent exchange
Figure 42.21
Gill arch
Waterflow Operculum
Gillarch
Bloodvessel
Gillfilaments
Oxygen-poorblood
Oxygen-richblood
Water flowover lamellaeshowing % O 2
Blood flowthrough capillariesin lamellaeshowing % O 2
Lamella
O 2
Tracheal Systems in Insects
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Figure 42.22a
Tracheae
Air sacs
Spiracle
(a) The respiratory system of an insect consists of branched internaltubes that deliver air directly to body cells. Rings of chitin reinforcethe largest tubes, called t racheae, keeping them from collapsing.Enlarged portions of tracheae form air sacs near organs that requirea large supply of oxygen. Air enters the tracheae through openingscalled spiracles on the insects body surface and passes into smallertubes called tracheoles. The tracheoles are closed and contain fluid(blue-gray). When the animal is active and is using more O 2, most ofthe fluid is withdrawn into the body. This increases the surface areaof air in contact with cells.
The tracheal system of insects
Consists of tiny branching tubes that penetratethe body
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The tracheal tubes
Supply O 2 directly to body cells Airsac
Bodycell
Trachea
Tracheole
Tracheoles MitochondriaMyofibrils
Body wall
(b) This micrograph shows crosssections of tracheoles in a tinypiece of insect flight muscle (TEM).Each of the numerous mitochondriain the muscle cells lies within about5 m of a tracheole.
Figure 42.22b 2.5 m
Air
Lungs
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Spiders, land snails, and most terrestrialvertebrates
Have internal lungs
M ammalian Respiratory Systems: A Cl oser L ook
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A system of branching ducts
Conveys air to the lungsBranchfrom thepulmonaryvein(oxygen-richblood)Terminalbronchiole
Branchfrom thepulmonaryartery(oxygen-poorblood)
Alveoli
Colorized SEMSEM
5 0 m
5 0 m
Heart
Leftlung
Nasalcavity
Pharynx
Larynx
Diaphragm
Bronchiole
Bronchus
Right lung
TracheaEsophagus
Figure 42.23
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In mammals, air inhaled through the nostrils
Passes through the pharynx into the trachea,bronchi, bronchioles, and dead-end alveoli,where gas exchange occurs
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How an Amphibian Breathes
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An amphibian such as a frog
Ventilates its lungs by positive pressurebreathing, which forces air down the trachea
How a Mammal Breathes
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Mammals ventilate their lungs
By negative pressure breathing, which pulls airinto the lungs
Air inhaled Air exhaled
INHALATION Diaphragm contracts
(moves down)
EXHALATION Diaphragm relaxes
(moves up)
Diaphragm
Lung
Rib cageexpands asrib musclescontract
Rib cage getssmaller asrib musclesrelax
Figure 42.24
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Lung volume increases
As the rib muscles and diaphragm contract
How a Bird Breathes
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Besides lungs, bird have eight or nine air sacs
That function as bellows that keep air flowingthrough the lungs
INHALATION Air sacs fill
EXHALATION Air sacs empty; lungs fill
Anteriorair sacs
Trachea
Lungs LungsPosteriorair sacs
Air Air
1 mm
Air tubes(parabronchi)in lung
Figure 42.25
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Air passes through the lungs
In one direction only Every exhalation
Completely renews the air in the lungs
Control of Breathing in Humans
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The main breathing control centers
Are located in two regions of the brain, themedulla oblongata and the pons
Figure 42.26
PonsBreathingcontrolcenters Medulla
oblongata
Diaphragm
Carotidarteries
Aorta
Cerebrospinalfluid
Rib muscles
In a person at rest, thesenerve impulses result in
about 10 to 14 inhalationsper minute. Between
inhalations, the musclesrelax and the person exhales.
The medullas control centeralso helps regulate blood CO 2 level.Sensors in the medulla detect changesin the pH (reflecting CO 2 concentration)of the blood and cerebrospinal fluidbathing the surface of the brain.
Nerve impulses relay changes inCO 2 and O 2 concentrations. Othersensors in the walls of the aortaand carotid arteries in the neckdetect changes in blood pH andsend nerve impulses to the medulla.In response, the medullas breathing control center alters the rate anddepth of breathing, increasing bothto dispose of excess CO 2 or decreasingboth if CO 2 levels are depressed.
The control center in themedulla sets the basic
rhythm, and a control centerin the pons moderates it,
smoothing out thetransitions between
inhalations and exhalations.
1
Nerve impulses triggermuscle contraction. Nerves
from a breathing control centerin the medulla oblongata of the
brain send impulses to thediaphragm and rib muscles,stimulating them to contract
and causing inhalation.
2
The sensors in the aorta andcarotid arteries also detect changesin O 2 levels in the blood and signalthe medulla to increase the breathingrate when levels become very low.
6
5
3
4
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The centers in the medulla
Regulate the rate and depth of breathing inresponse to pH changes in the cerebrospinalfluid
The medulla adjusts breathing rate and depth To match metabolic demands
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Sensors in the aorta and carotid arteries
Monitor O 2 and CO 2 concentrations in theblood
Exert secondary control over breathing
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Concept 42.7: Respiratory pigments bind andtransport gases
The metabolic demands of many organisms
Require that the blood transport large
quantities of O 2 and CO 2
The Role of Partial Pressure Gradients
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Gases diffuse down pressure gradients
In the lungs and other organs Diffusion of a gas
Depends on differences in a quantity calledpartial pressure
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A gas always diffuses from a region of higherpartial pressure
To a region of lower partial pressure
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In the lungs and in the tissues
O 2 and CO 2 diffuse from where their partialpressures are higher to where they are lower
Inhaled air Exhaled air
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Inhaled air Exhaled air
160 0.2O2 CO 2
O2 CO 2
O2 CO 2
O2 CO 2 O2 CO 2
O2 CO 2 O2 CO 2
O2 CO 2
40 45
40 45
100 40
104 40
104 40
120 27
CO 2 O2
Alveolarepithelialcells
Pulmonary
arteries
Bloodenteringalveolar
capillaries
Bloodleavingtissue
capillaries
Bloodentering
tissuecapillaries
Bloodleavingalveolar
capillaries
CO 2 O2
Tissuecapillaries
Heart
Alveolarcapillaries
of lung
45
Tissuecells
Pulmonaryveins
SystemicarteriesSystemic
veinsO2
CO 2
O2
Alveolar spaces
12
43
Figure 42.27
Respiratory Pigments
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Respiratory pigments
Are proteins that transport oxygen Greatly increase the amount of oxygen that
blood can carry
Oxygen Transpor t
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The respiratory pigment of almost allvertebrates
Is the protein hemoglobin, contained in theerythrocytes
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Like all respiratory pigments
Hemoglobin must reversibly bind O 2, loadingO 2 in the lungs and unloading it in other partsof the body
Heme group Iron atom
O2 loadedin lungs
O 2 unloadedIn tissues
Polypeptide chain
O 2
O2
Figure 42.28
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Loading and unloading of O 2
Depend on cooperation between the subunitsof the hemoglobin molecule
The binding of O 2 to one subunit induces the
other subunits to bind O 2 with more affinity
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Cooperative O 2 binding and release
Is evident in the dissociation curve forhemoglobin
A drop in pH
Lowers the affinity of hemoglobin for O 2
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O2 unloaded fromhemoglobinduring normalmetabolism
O 2 reserve that can
be unloaded fromhemoglobin totissues with highmetabolism
Tissues duringexercise
Tissuesat rest
100
80
60
40
20
0
100
80
60
40
20
0
100806040200
100806040200
Lungs
P O2 (mm Hg)
P O2 (mm Hg)
O 2
s a t u r a
t i o n o
f h e m o g
l o b i n ( % )
O 2
s a t u r a
t i o n o
f h e m
o g
l o b i n ( % )
Bohr shift: Additional O 2 released fromhemoglobin atlower pH(higher CO 2 concentration)
pH 7.4
pH 7.2
(a) P O2 and Hemoglobin Dissociation at 37C and pH 7.4
(b) pH and Hemoglobin Dissociation
Figure 42.29a, b
Carbon Dioxide Transpor t
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Hemoglobin also helps transport CO 2
And assists in buffering
b f ll
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Carbon from respiring cells
Diffuses into the blood plasma and then intoerythrocytes and is ultimately released in thelungs
Tissue cellCO 2 transportCarbon dioxide produced by Most of the HCO diffuse1 7
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Figure 42.30
CO 2 Interstitialfluid
CO 2 producedCO 2 t a spo tfrom tissues
CO 2
CO 2
Blood plasma
within capillaryCapillarywall
H2O
Redbloodcell
HbCarbonic acidH2CO 3
HCO 3 H+ +Bicarbonate
HCO 3
Hemoglobinpicks up
CO 2 and H+
HCO 3
HCO 3 H+
+
H2CO 3Hb
Hemoglobinreleases
CO 2 and H+
CO 2 transportto lungs
H2O
CO 2
CO 2
CO 2
CO 2
Alveolar space in lung
2
1
3 4
5 6
7
8
9
10
11
To lungs
Carbon dioxide produced bybody tissues diffuses into theinterstitial fluid and the plasma.
Over 90% of the CO 2 diffuses
into red blood cells, leaving only 7%in the plasma as dissolved CO 2.
Some CO 2 is picked up andtransported by hemoglobin.
However, most CO 2 reacts with water
in red blood cells, forming carbonicacid (H 2CO 3), a reaction catalyzed bycarbonic anhydrase contained. Withinred blood cells.
Carbonic acid dissociates into abiocarbonate ion (HCO 3 ) and ahydrogen ion (H +).
Hemoglobin binds most of theH+ from H 2CO 3 preventing the H + from acidifying the blood and thuspreventing the Bohr shift.
CO 2 diffuses into the alveolarspace, from which it is expelledduring exhalation. The reductionof CO 2 concentration in the plasma
drives the breakdown of H 2CO 3Into CO 2 and water in the red bloodcells (see step 9), a reversal of thereaction that occurs in the tissues(see step 4).
Most of the HCO 3 diffuseinto the plasma where it iscarried in the bloodstream tothe lungs.
In the HCO 3 diffusefrom the plasma red blood cells,combining with H + released fromhemoglobin and forming H 2CO 3.
Carbonic acid is converted backinto CO 2 and water.
CO 2 formed from H 2CO 3 is unloadedfrom hemoglobin and diffuses into theinterstitial fluid.
1
2
3
4
5
6
7
8
9
10
11
Elite Animal Athletes
Mi d di i l
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Migratory and diving mammals
Have evolutionary adaptations that allow themto perform extraordinary feats
The Ultimate Endur ance Runner
Th O i f h l
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The extreme O 2 consumption of the antelope-like pronghorn
Underlies its ability to run at high speed overlong distances
Figure 42.31
Diving M ammals
D di i i b h
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Deep-diving air breathers
Stockpile O 2 and deplete it slowly