Chapter42 Circulation and Gas Exchange

8/13/2019 Chapter42 Circulation and Gas Exchange

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Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

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


7/108Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Invertebrate Circulation

The wide range of invertebrate body size and

form Is paralleled by a great diversity in circulatory

systems



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



Some cnidarians, such as jellies

Have elaborate gastrovascular cavities

Figure 42.2

Circularcanal

Radial canal

5 cmMouth



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)



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



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



Closed systems

Are more efficient at transporting circulatoryfluids to tissues and cells



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


105/108


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


106/108


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


108/108

Deep-diving air breathers

Stockpile O 2 and deplete it slowly

Chapter42 Circulation and Gas Exchange

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Transcript of Chapter42 Circulation and Gas Exchange