biology in focus - chapter 34
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CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge
34Circulation and Gas Exchange
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Overview: Trading Places
The resources that animal cells require, such as nutrients and O2, enter the cytoplasm by crossing the plasma membrane
In unicellular organisms, these exchanges occur directly with the environment
Most multicellular organisms rely on specialized systems that carry out exchange with the environment and transport materials through the body
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Gills are an example of a specialized exchange system in animals O2 diffuses from the water into blood vessels
CO2 diffuses from blood into the water
Internal transport and gas exchange are functionally related in most animals
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Figure 34.1
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Concept 34.1: Circulatory systems link exchange surfaces with cells throughout the body
Small, nonpolar molecules such as O2 and CO2 move between cells and their immediate surroundings by diffusion
Diffusion time is proportional to the square of the distance travelled
Diffusion is only efficient over small distances
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In small or thin animals, cells can exchange materials directly with the surrounding medium
In most animals, cells exchange materials with the environment via a fluid-filled circulatory system
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Gastrovascular Cavities
Some animals lack a circulatory system Some cnidarians, such as jellies, have elaborate
gastrovascular cavities A gastrovascular cavity functions in both digestion
and distribution of substances throughout the body The body wall that encloses the gastrovascular
cavity is only two cells thick Flatworms have a gastrovascular cavity and a flat
body shape to optimize diffusional exchange with the environment
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Figure 34.2
Gastrovascularcavity
Mouth
1 mm
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Open and Closed Circulatory Systems
A circulatory system has a circulatory fluid, a set of interconnecting vessels, and a muscular pump, the heart
Several basic types of circulatory systems have arisen during evolution, each representing adaptations to constraints of anatomy and environment
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All circulatory systems are either open or closed In insects, other arthropods, and some molluscs,
circulatory fluid bathes the organs directly in an open circulatory system
In an open circulatory system, there is no distinction between circulatory fluid and interstitial fluid, and this general body fluid is called hemolymph
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Figure 34.3
Branch vesselsin each organ
Tubular heart
Pores
Hemolymph in sinuses
(a) An open circulatory system
Heart
(b) A closed circulatory system
HeartBlood
Dorsal vessel(main heart)
Auxiliaryhearts
Ventral vessels
Interstitialfluid
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Figure 34.3a
Tubular heart
Pores
Hemolymph in sinuses
(a) An open circulatory system
Heart
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In closed circulatory systems the circulatory fluid called blood is confined to vessels and is distinct from interstitial fluid
These systems are found in annelids, most cephalopods, and all vertebrates
One or more hearts pump blood through the vessels Chemical exchange occurs between blood and
interstitial fluid and between interstitial fluid and body cells
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Figure 34.3b
Branch vesselsin each organ
(b) A closed circulatory system
HeartBlood
Dorsal vessel(main heart)
Auxiliaryhearts
Ventral vessels
Interstitialfluid
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Organization of Vertebrate Circulatory Systems
Humans and other vertebrates have a closed circulatory system called the cardiovascular system
The three main types of blood vessels are arteries, veins, and capillaries
Blood flow is one-way in these vessels
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Arteries branch into arterioles and carry blood away from the heart to capillaries
Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid
Venules converge into veins and return blood from capillaries to the heart
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Arteries and veins are distinguished by the direction of blood flow, not by O2 content
Vertebrate hearts contain two or more chambers Blood enters through an atrium and is pumped out
through a ventricle
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Single Circulation
Bony fishes, rays, and sharks have single circulation with a two-chambered heart
In single circulation, blood leaving the heart passes through two capillary beds before returning
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Figure 34.4
Lungand skincapillaries
Body capillaries
Vein
Gill capillaries
(a) Single circulation: fish
Heart:
(b) Double circulation:amphibian
Key
Systemiccapillaries
Pulmocutaneous circuit
Artery
Ventricle (V)Atrium (A)
Oxygen-rich bloodOxygen-poor blood
Right Left
A A
V
Systemic circuit
Lungcapillaries
(c) Double circulation:mammal
Systemiccapillaries
Pulmonary circuit
Right Left
A AV
Systemic circuit
V
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Figure 34.4a
Body capillaries
Vein
Gill capillaries
(a) Single circulation: fish
Heart:
Key
Artery
Ventricle (V)Atrium (A)
Oxygen-rich bloodOxygen-poor blood
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Double Circulation
Amphibians, reptiles, and mammals have double circulation
Oxygen-poor and oxygen-rich blood is pumped separately from the right and left sides of the heart
Having both pumps within a heart simplifies coordination of the pumping cycle
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Figure 34.4b
Lungand skincapillaries
(b) Double circulation:amphibian
Key
Systemiccapillaries
Pulmocutaneous circuit
Oxygen-rich bloodOxygen-poor blood
Right Left
A A
V
Systemic circuit
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Figure 34.4c
KeyOxygen-rich bloodOxygen-poor blood
Lungcapillaries
(c) Double circulation:mammal
Systemiccapillaries
Pulmonary circuit
Right Left
A AV
Systemic circuit
V
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In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs
In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin
Oxygen-rich blood delivers oxygen through the systemic circuit
Double circulation maintains higher blood pressure in the organs than does single circulation
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Evolutionary Variation in Double Circulation
Some vertebrates with double circulation are intermittent breathers
These animals have adaptations that enable the circulatory system temporarily to bypass the lungs
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Frogs and other amphibians have a three-chambered heart: two atria and one ventricle
The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit
When underwater, blood flow to the lungs is nearly shut off
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Turtles, snakes, and lizards have a three-chambered heart: two atria and one ventricle
Their circulatory system allows control of relative amounts of blood flowing to the lungs and body
In alligators, caimans, and other crocodilians a septum divides the ventricle
A connection to atrial valves can temporarily shunt blood away from the lungs, as needed
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Mammals and birds have a four-chambered heart with two atria and two ventricles
The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood
There is no mechanism to vary relative blood flow to the lungs and body
Mammals and birds are endotherms and require more O2 than ectotherms
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Concept 34.2: Coordinated cycles of heart contraction drive double circulation in mammals
The mammalian cardiovascular system meets the body’s continuous demand for O2
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Mammalian Circulation
Blood begins its flow with the right ventricle pumping blood to the lungs via the pulmonary arteries
The blood loads O2 and unloads CO2 in the capillary beds of the lungs
Oxygen-rich blood from the lungs enters the heart at the left atrium via the pulmonary veins and is pumped through the aorta to the body tissues by the left ventricle
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The aorta provides blood to the heart through the coronary arteries
Diffusion of O2 and CO2 takes place in the capillary beds throughout the body
Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs)
The superior vena cava and inferior vena cava flow into the right atrium
Animation: Path of Blood Flow
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Figure 34.5
Capillaries ofabdominal organsand hind limbs
Aorta
Capillariesof right lung
Superiorvena cava
Pulmonaryartery
PulmonaryveinRight atriumRight ventricleInferior vena cava
Capillariesof left lung
Pulmonary artery
Pulmonaryvein
Left atriumLeft ventricle
Capillaries ofhead andforelimbs
Aorta9
7
6
42
11
3
5
8
101
3
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The Mammalian Heart: A Closer Look
A closer look at the mammalian heart provides a better understanding of double circulation
When the heart contracts, it pumps blood; when it relaxes, its chambers fill with blood
One complete sequence of pumping and filling is called the cardiac cycle
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Atria have relatively thin walls and serve as collection chambers for blood returning to the heart
The ventricles are more muscular and contract much more forcefully than the atria
The volume of blood each ventricle pumps per minute is called the cardiac output
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Figure 34.6
Aorta
Atrioventricular(AV) valve
Semilunarvalve
Pulmonary artery
Rightatrium
Right ventricle
Pulmonary artery
Left atrium
Left ventricle
Atrioventricular(AV) valve
Semilunarvalve
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Figure 34.7-1
Atrial andventriculardiastole
0.4sec
1
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Figure 34.7-2
Atrial andventriculardiastole
Atrial systole andventricular diastole
0.4sec
0.1sec
1
2
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Figure 34.7-3
Atrial andventriculardiastole
Atrial systole andventricular diastole
Ventricular systole and atrial diastole
0.4sec
0.3 sec
0.1sec
1
2
3
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The heart rate, also called the pulse, is the number of beats per minute
The stroke volume is the amount of blood pumped in a single contraction
Cardiac output depends on both the heart rate and stroke volume
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Four valves prevent backflow of blood in the heart The atrioventricular (AV) valves separate each
atrium and ventricle The semilunar valves control blood flow to the
aorta and the pulmonary artery
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The “lub-dup” sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves
Backflow of blood through a defective valve causes a heart murmur
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Maintaining the Heart’s Rhythmic Beat
Some cardiac muscle cells are autorhythmic, meaning they contract without any signal from the nervous system
The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which all other cardiac muscle cells contract
The SA node produces electrical impulses that spread rapidly through the heart and can be recorded as an electrocardiogram (ECG or EKG)
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Figure 34.8-1
Signals (yellow)from SA nodespreadthrough atria.
SA node(pacemaker)
1
ECG
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Figure 34.8-2
Signals (yellow)from SA nodespreadthrough atria.
SA node(pacemaker)
1 Signals aredelayedat AV node.
AV node
ECG
2
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Figure 34.8-3
Signals (yellow)from SA nodespreadthrough atria.
SA node(pacemaker)
1 Signals aredelayedat AV node.
Bundlebranchespass signalsto heart apex.
AV node
Bundlebranches Heart
apexECG
2 3
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Figure 34.8-4
Signals (yellow)from SA nodespreadthrough atria.
SA node(pacemaker)
1 Signals aredelayedat AV node.
Bundlebranchespass signalsto heart apex.
Signalsspreadthroughoutventricles.
AV node
Bundlebranches Heart
apex
Purkinjefibers
ECG
2 3 4
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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 pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions
The sympathetic division speeds up the pacemaker The parasympathetic division slows down the
pacemaker The pacemaker is also regulated by hormones and
temperature
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Concept 34.3: Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels
The physical principles that govern movement of water in plumbing systems also apply to the functioning of animal circulatory systems
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Blood Vessel Structure and Function
A vessel’s cavity is called the central lumen The epithelial layer that lines blood vessels is called
the endothelium The endothelium is smooth and minimizes resistance
to blood flow
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Capillaries have thin walls, the endothelium and its basal lamina, to facilitate the exchange of substances
Arteries and veins have an endothelium, smooth muscle, and connective tissue
Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart
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Figure 34.9
Connectivetissue
Smoothmuscle
Connectivetissue
Smoothmuscle
Endothelium Endothelium
Artery Vein
Artery Vein
Red bloodcells
Basal lamina
Capillary
Red blood cell
Capillary
ArterioleVenule
Valve100 m
15
m
LMLM
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Figure 34.9a
Connectivetissue
Smoothmuscle
Connectivetissue
Smoothmuscle
EndotheliumEndothelium
Artery Vein
Basal lamina
Capillary
ArterioleVenule
Valve
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Figure 34.9b
Artery Vein
Red bloodcells
100 m
LM
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Figure 34.9c
Red blood cell
Capillary
15
mLM
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Blood Flow Velocity
Blood vessel diameter influences blood flow Velocity of blood flow is slowest in the capillary
beds, as a result of the high resistance and large total cross-sectional area
Blood flow in capillaries is necessarily slow for exchange of materials
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Figure 34.10
Systolicpressure
Diastolicpressure
4,0002,000
120
2040
80400
0
0
Pres
sure
(mm
Hg)
Velo
city
(cm
/sec
)A
rea
(cm
2 )
Aor
ta
Art
erie
s
Vena
eca
vae
Vein
s
Cap
illar
ies
Venu
les
Art
erio
les
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Blood Pressure
Blood flows from areas of higher pressure to areas of lower pressure
Blood pressure exerts a force in all directions
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Changes in Blood Pressure During the Cardiac Cycle
Systole is the contraction phase of the cardiac cycle Pressure at the time of ventricle contraction is called
systolic pressure Diastole is the the relaxation phase of the cardiac
cycle; diastolic pressure is lower than systolic
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Maintenance of Blood Pressure
Blood pressure is determined by cardiac output and peripheral resistance due to constriction of arterioles
Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood pressure
Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall
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Vasoconstriction and vasodilation help maintain adequate blood flow as the body’s demands change
Nitric oxide is a major inducer of vasodilation The peptide endothelin is an important inducer of
vasoconstriction
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Fainting is caused by inadequate blood flow to the head
Animals with long necks require a higher systolic pressure to pump blood against gravity
Gravity is a consideration for blood flow in veins, particularly in the legs
One-way valves in veins prevent backflow of blood Blood returns to the heart through contraction of
smooth muscle in the walls of veins and venules and by contraction of skeletal muscles
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Figure 34.11
Direction of bloodflow in vein(toward heart)
Valve (open)
Valve (closed)
Skeletal muscle
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Capillary Function
Blood flows through only 5–10% of the body’s capillaries at a time
Capillaries in major organs are usually filled to capacity
Blood supply varies in many other sites
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Two mechanisms alter blood flow in capillary beds Vasoconstriction or vasodilation of the arteriole that
supplies a capillary bed Precapillary sphincters, rings of smooth muscle at the
capillary bed entrance, open and close to regulate passage of blood
Critical exchange of substances takes place across the thin walls of the capillaries
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Blood pressure tends to drive fluid out of the capillaries
The difference in solute concentration between blood and interstitial fluid (the blood’s osmotic pressure) opposes fluid movement from the capillaries
Blood pressure is usually greater than osmotic pressure
Net loss of fluid from capillaries occurs in regions where blood pressure is highest
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Fluid Return by the Lymphatic System
The lymphatic system returns fluid, called lymph, that leaks out from the capillary beds
Lymph has a very similar composition to interstitial fluid
The lymphatic system drains into veins in the neck Valves in lymph vessels prevent the backflow of
fluid
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Figure 34.12Interstitialfluid
Lymphaticvessel
Lymphaticvessel
Bloodcapillary
Tissue cells
Lymph nodeMasses ofdefensivecells
Lymphaticvessels
Lymph nodes
Peyer’s patches(small intestine)
Appendix(cecum)
Thymus(immunesystem)
AdenoidTonsils
Spleen
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Lymph vessels have valves to prevent backflow Lymph nodes are organs that filter lymph and play
an important role in the body’s defense Edema is swelling caused by disruptions in the flow
of lymph The lymphatic system also plays a role in harmful
immune responses, such as those responsible for asthma
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Concept 34.4: Blood components function in exchange, transport, and defense
With open circulation, the fluid that is pumped comes into direct contact with all cells and has the same composition as interstitial fluid
The closed circulatory systems of vertebrates contain blood, which can be much more highly specialized
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Blood Composition and Function
Blood is a connective tissue consisting of cells suspended in a liquid matrix called plasma
The cellular elements occupy about 45% of the volume of blood
Video: Leukocyte Rolling
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Figure 34.13
Separatedbloodelements
Solvent forcarrying othersubstances
Plasma 55% Cellular elements 45%
Constituent Major functions
Osmotic balance,pH buffering,and regulationof membranepermeability
Water
Ions (bloodelectrolytes)SodiumPotassiumCalciumMagnesiumChlorideBicarbonate
Osmotic balance,pH buffering
Clotting
Defense
Fibrinogen
Plasma proteinsAlbumin
Immunoglobulins(antibodies)
Substances transported by bloodNutrients (such as glucose, fattyacids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones
Functions
Leukocytes (white blood cells)
Transportof O2 and some CO2
Cell typeNumber
per L (mm3)of blood
Basophils Lymphocytes
Eosinophils
Neutrophils Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5,000,000– 6,000,000
Bloodclotting
5,000–10,000 Defenseandimmunity
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Figure 34.13a
Solvent for carrying othersubstances
Plasma 55%Constituent Major functions
Osmotic balance, pH buffering,and regulation of membranepermeability
Water
Ions (blood electrolytes)SodiumPotassiumCalciumMagnesiumChlorideBicarbonate
Osmotic balance, pH buffering
Clotting
Defense
Fibrinogen
Plasma proteinsAlbumin
Immunoglobulins(antibodies)
Substances transported by bloodNutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones
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Figure 34.13b
Cellular elements 45%
Functions
Leukocytes (white blood cells)
Transport of O2 and some CO2
Cell type Numberper L (mm3) of blood
Basophils Lymphocytes
Eosinophils
Neutrophils Monocytes
Platelets
Erythrocytes (red blood cells)
250,000–400,000
5,000,000–6,000,000
Blood clotting
5,000–10,000 Defense andimmunity
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Plasma
Blood plasma is about 90% water Among its solutes are inorganic salts in the form of
dissolved ions, sometimes called electrolytes Plasma proteins influence blood pH, osmotic
pressure, and viscosity Particular plasma proteins function in lipid transport,
immunity, and blood clotting
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Cellular Elements
Blood contains two classes of cells Red blood cells (erythrocytes) transport O2
White blood cells (leukocytes) function in defense
Platelets, a third cellular element, are fragments of cells that are involved in clotting
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Figure 34.14
Stem cells(in bone marrow)
BasophilsLymphocytes
Eosinophils
Neutrophils
MonocytesPlatelets
Erythrocytes
Myeloidstem cells
Lymphoidstem cells
B cells T cells
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Erythrocytes Red blood cells, or erythrocytes, are by far the most
numerous blood cells They contain hemoglobin, the iron-containing
protein that transports O2
Each molecule of hemoglobin binds up to four molecules of O2
In mammals, mature erythrocytes lack nuclei
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Sickle-cell disease is caused by abnormal hemoglobin that polymerizes into aggregates
The aggregates can distort an erythrocyte into a sickle shape
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Through a person’s life, multipotent stem cells replace the worn-out cellular elements of blood
Erythrocytes circulate for about 120 days before they are replaced
Stem cells that produce red blood cells and platelets are located in red marrow of bones like the ribs, vertebrae, sternum, and pelvis
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Leukocytes There are five major types of white blood cells, or
leukocytes They function in defense by engulfing bacteria and
debris or by mounting immune responses against foreign substances
They are found both in and outside of the circulatory system
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Platelets Platelets are fragments of cells and function in
blood clotting
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Blood Clotting
Coagulation is the formation of a solid clot from liquid blood
A cascade of complex reactions converts inactive fibrinogen to fibrin, which forms the framework of a clot
A blood clot formed within a blood vessel is called a thrombus and can block blood flow
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Figure 34.15
PlateletPlateletplug
Collagenfibers
PlateletsClotting factors from:
Damaged cellsPlasma (factors include calcium, vitamin K)
Fibrin
Thrombin
Fibrinogen
Prothrombin
Enzymatic cascade
Fibrin clot
Fibrin clotformation
Red blood cell 5 m
1 2 3
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Figure 34.15a
PlateletPlateletplug
Collagenfibers
PlateletsClotting factors from:
Damaged cellsPlasma (factors include calcium, vitamin K)
Fibrin
Thrombin
Fibrinogen
Prothrombin
Enzymatic cascade
Fibrin clot
Fibrin clotformation
1 2 3
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Figure 34.15b
Fibrin clot
Red blood cell 5 m
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Cardiovascular Disease
Cardiovascular diseases are disorders of the heart and the blood vessels
Cardiovascular diseases account for more than half the deaths in the United States
Cholesterol, a steroid, helps maintain normal membrane fluidity
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Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production
High-density lipoprotein (HDL) scavenges excess cholesterol for return to the liver
Risk for heart disease increases with a high LDL to HDL ratio
Inflammation is also a factor in cardiovascular disease
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Atherosclerosis, Heart Attacks, and Stroke
One type of cardiovascular disease, atherosclerosis, is caused by the buildup of fatty deposits within arteries
A fatty deposit is called a plaque; as it grows, the artery walls become thick and stiff and the obstruction of the artery increases
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Figure 34.16
Endothelium
Lumen
Plaque
Blood clot
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A heart attack, or myocardial infarction, is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries
Coronary arteries supply oxygen-rich blood to the heart muscle
A stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head
Angina pectoris is caused by partial blockage of the coronary arteries and may cause chest pain
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Risk Factors and Treatment of Cardiovascular Disease
A high LDL to HDL ratio increases the risk of cardiovascular disease
The proportion of LDL relative to HDL is increased by smoking and consumption of trans fats and decreased by exercise
Drugs called statins reduce LDL levels and risk of heart attacks
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Inflammation plays a role in atherosclerosis and thrombus formation
Aspirin inhibits inflammation and reduces the risk of heart attacks and stroke
Hypertension (high blood pressure) contributes to the risk of heart attack and stroke
Hypertension can be reduced by dietary changes, exercise, medication, or some combination of these
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Concept 34.5: Gas exchange occurs across specialized respiratory surfaces
Gas exchange is the uptake of molecular O2 from the environment and the discharge of CO2 to the environment
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Partial Pressure Gradients in Gas Exchange
Partial pressure is the pressure exerted by a particular gas in a mixture of gases
For example, the atmosphere is 21% O2, by volume, so the partial pressure of O2 (PO2
) is 0.21 the
atmospheric pressure
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Partial pressures also apply to gases dissolved in liquid, such as water
When water is exposed to air, an equilibrium is reached in which the partial pressure of each gas is the same in the water and the air
A gas always undergoes net diffusion from a region of higher partial pressure to a region of lower partial pressure
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Respiratory Media
O2 is plentiful in air, and breathing air is relatively easy
In a given volume, there is less O2 available in water than in air
Obtaining O2 from water requires greater energy expenditure than air breathing
Aquatic animals have a variety of adaptations to improve efficiency in gas exchange
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Figure 34.17
Coelom
Tube foot
Gills
(b) Sea star(a) Marine worm
Parapodium (functions as gill)
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Figure 34.17a
(a) Marine worm
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Figure 34.17b
(b) Sea star
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Respiratory Surfaces
Gas exchange across respiratory surfaces takes place by diffusion
Respiratory surfaces tend to be large and thin and are always moist
Respiratory surfaces vary by animal and can include the skin, gills, tracheae, and lungs
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Gills in Aquatic Animals
Gills are outfoldings of the body that create a large surface area for gas exchange
Ventilation is the movement of the respiratory medium over the respiratory surface
Ventilation maintains the necessary partial pressure gradients of O2 and CO2 across the gills
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Aquatic animals move through water or move water over their gills for ventilation
Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills
Blood is always less saturated with O2 than the water it meets
Countercurrent exchange mechanisms are remarkably efficient
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Figure 34.18
Lamella
Water flow
Countercurrent exchange
O2-poor blood
Gill filaments
Operculum
Gillarch
Waterflow
Gill arch
Bloodvessels
O2-rich blood
Blood flow
PO2 (mm Hg)
in blood
PO2 (mm Hg) in water
Netdiffusionof O2
140 110 80 50 30
150 120 90 60 30
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Tracheal Systems in Insects
The tracheal system of insects consists of a network of air tubes that branch throughout the body
The tracheal system can transport O2 and CO2 without the participation of the animal’s open circulatory system
Larger insects must ventilate their tracheal system to meet O2 demands
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Figure 34.19 Tracheoles Muscle fiberMitochondria
Tracheae
Air sacs
External opening
Airsac Tracheole
Trachea
Air2.
5 m
Bodycell
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Figure 34.19a
Tracheoles Muscle fiberMitochondria
2.5
m
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Lungs
Lungs are an infolding of the body surface, usually divided into numerous pockets
The circulatory system (open and closed) transports gases between the lungs and the rest of the body
The use of lungs for gas exchange varies among vertebrates that lack gills
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Mammalian Respiratory Systems: A Closer Look
A system of branching ducts conveys air to the lungs Air inhaled through the nostrils is warmed,
humidified, and sampled for odors The pharynx directs air to the lungs and food to the
stomach Swallowing tips the epiglottis over the glottis in the
pharynx to prevent food from entering the trachea
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Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs
Exhaled air passes over the vocal cords in the larynx to create sounds
Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx
This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the esophagus
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Gas exchange takes place in alveoli, air sacs at the tips of bronchioles
Oxygen diffuses through the moist film of the epithelium and into capillaries
Carbon dioxide diffuses from the capillaries across the epithelium and into the air space
Animation: Gas Exchange
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Figure 34.20
Bronchiole
Bronchus
Right lungTrachea(Esophagus)Larynx
Pharynx
(Heart)
Terminalbronchiole
Leftlung
Nasalcavity
Capillaries
Alveoli
Dense capillary bedenveloping alveoli(SEM)
Branch ofpulmonary vein(oxygen-richblood)
Branch of pulmonary artery (oxygen-poorblood)
50 m
Diaphragm
© 2014 Pearson Education, Inc.
Figure 34.20a
Bronchiole
Bronchus
Right lungTrachea(Esophagus)Larynx
Pharynx
(Heart)
Leftlung
Nasalcavity
Diaphragm
© 2014 Pearson Education, Inc.
Figure 34.20b
Terminalbronchiole
Capillaries
Alveoli
Branch ofpulmonary vein(oxygen-richblood)
Branch of pulmonary artery (oxygen-poorblood)
© 2014 Pearson Education, Inc.
Figure 34.20c
Dense capillary bedenveloping alveoli (SEM)
50 m
© 2014 Pearson Education, Inc.
Alveoli lack cilia and are susceptible to contamination Secretions called surfactants coat the surface of
the alveoli Preterm babies lack surfactant and are vulnerable to
respiratory distress syndrome; treatment is provided by artificial surfactants
© 2014 Pearson Education, Inc.
Figure 34.21
Deaths fromother causes
RDS deaths
Body mass of infant<1,200 g >1,200 g
(n 9) (n 0) (n 29) (n 9)
Surf
ace
tens
ion
(dyn
es/c
m)
Results
10
20
30
40
0
© 2014 Pearson Education, Inc.
Concept 34.6: Breathing ventilates the lungs
The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air
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An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the trachea
Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs
Air passes through the lungs of birds in one direction only
Passage of air through the entire system—lungs and air sacs—requires two cycles in inhalation and exhalation
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How a Mammal Breathes
Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs
Lung volume increases as the rib muscles and diaphragm contract
The tidal volume is the volume of air inhaled with each breath
Animation: Gas Exchange
© 2014 Pearson Education, Inc.
Figure 34.22
Inhalation:Diaphragm contracts
(moves down).
Diaphragm
Exhalation:Diaphragm relaxes
(moves up).
Lung
Airinhaled.
Airexhaled.
Rib cageexpands asrib musclescontract.
Rib cage getssmaller asrib musclesrelax.
1 2
© 2014 Pearson Education, Inc.
The maximum tidal volume is the vital capacity After exhalation, a residual volume of air remains
in the lungs Each inhalation mixes fresh air with oxygen-depleted
residual air
As a result, the maximum PO2 in alveoli is
considerably less than in the atmosphere
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Control of Breathing in Humans
In humans, the main breathing control center consists of neural circuits in the medulla oblongata, near the base of the brain
The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid
The medulla adjusts breathing rate and depth to match metabolic demands
© 2014 Pearson Education, Inc.
Figure 34.23-1
Homeostasis:Blood pH of about 7.4
Stimulus:Rising level of CO2in tissues lowers
blood pH.
© 2014 Pearson Education, Inc.
Figure 34.23-2
Carotidarteries
Homeostasis:Blood pH of about 7.4
Stimulus:Rising level of CO2in tissues lowers
blood pH.
Sensor/controlcenter:
AortaCerebro-spinalfluid
Medullaoblongata
© 2014 Pearson Education, Inc.
Figure 34.23-3
Carotidarteries
Response:Signals frommedulla to ribmuscles anddiaphragmincrease rateand depth ofventilation.
Homeostasis:Blood pH of about 7.4
Stimulus:Rising level of CO2in tissues lowers
blood pH.
Sensor/controlcenter:
AortaCerebro-spinalfluid
Medullaoblongata
© 2014 Pearson Education, Inc.
Figure 34.23-4
Carotidarteries
Response:Signals frommedulla to ribmuscles anddiaphragmincrease rateand depth ofventilation.
Homeostasis:Blood pH of about 7.4
CO2 leveldecreases. Stimulus:
Rising level of CO2in tissues lowers
blood pH.
Sensor/controlcenter:
AortaCerebro-spinalfluid
Medullaoblongata
© 2014 Pearson Education, Inc.
Sensors in the aorta and carotid arteries monitor O2 and CO2 concentrations in the blood
These sensors exert secondary control over breathing
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Concept 34.7: Adaptations for gas exchange include pigments that bind and transport gases
The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2
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Coordination of Circulation and Gas Exchange
Blood arriving in the lungs has a low PO2 and a high
PCO2 relative to air in the alveoli
In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air
In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood
Specialized carrier proteins play a vital role in this process
© 2014 Pearson Education, Inc.
Animation: O2 Blood to Tissues
Animation: O2 Lungs to Blood
Animation: CO2 Blood to Lungs
Animation: CO2 Tissues to Blood
© 2014 Pearson Education, Inc.
Figure 34.24
Alveolarepithelialcells
Alveolarspaces
Alveolarcapillaries
Inhaled airExhaled air
Pulmonaryveins
Systemicarteries
Pulmonaryarteries
Systemicveins
Systemiccapillaries
Heart
CO2 O2
Body tissuecells
O2 CO2
120 27
O2 CO2
40 45
O2 CO2
160 0.2
O2 CO2
104 40
O2 CO2
<40 >45
O2CO2
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Respiratory Pigments
Respiratory pigments circulate in blood or hemolymph and greatly increase the amount of oxygen that is transported
A variety of respiratory pigments have evolved among animals
These mainly consist of a metal bound to a protein
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The respiratory pigment of almost all vertebrates and many invertebrates is hemoglobin
A single hemoglobin molecule can carry four molecules of O2, one molecule for each iron- containing heme group
Hemoglobin binds oxygen reversibly, loading it in the gills or lungs and releasing it in other parts of the body
© 2014 Pearson Education, Inc.
Figure 34.UN01
Hemoglobin
Heme
Iron
© 2014 Pearson Education, Inc.
Hemoglobin binds O2 cooperatively
When O2 binds one subunit, the others change shape slightly, resulting in their increased affinity for oxygen
When one subunit releases O2, the others release their bound O2 more readily
Cooperativity can be demonstrated by the dissociation curve for hemoglobin
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Figure 34.25
pH 7.4
PO2 (mm Hg)
pH 7.2
Hemoglobinretains lessO2 at lower pH(higher CO2
concentration
Tissuesat restPO2
(mm Hg)
Tissues duringexercise
Lungs
O2 unloadedto tissues
during exercise
O2 unloadedto tissuesat rest
(b) pH and hemoglobin dissociation(a) PO2 and hemoglobin dissociation
at pH 7.4
O2 sa
tura
tion
of h
emog
lobi
n (%
)
O2 sa
tura
tion
of h
emog
lobi
n (%
) 100
80
60
40
20
0
100
80
60
40
20
0100806040200 100806040200
© 2014 Pearson Education, Inc.
Figure 34.25a
Tissuesat restPO2
(mm Hg)
Tissues duringexercise
Lungs
O2 unloadedto tissues
during exercise
O2 unloadedto tissuesat rest
(a) PO2 and hemoglobin dissociation
at pH 7.4
O2 sa
tura
tion
of h
emog
lobi
n (%
)
100
80
60
40
20
0100806040200
© 2014 Pearson Education, Inc.
CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2; this is called the Bohr shift
Hemoglobin also assists in preventing harmful changes in blood pH and plays a minor role in CO2 transport
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Figure 34.25b
pH 7.4
PO2 (mm Hg)
pH 7.2
Hemoglobinretains lessO2 at lower pH(higher CO2
concentration
(b) pH and hemoglobin dissociation
O2 sa
tura
tion
of h
emog
lobi
n (%
)
100
80
60
40
20
0100806040200
© 2014 Pearson Education, Inc.
Carbon Dioxide Transport
Most of the CO2 from respiring cells diffuses into the blood and is transported in blood plasma, bound to hemoglobin or as bicarbonate ions (HCO3
–)
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Respiratory Adaptations of Diving Mammals
Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats For example, Weddell seals in Antarctica can remain
underwater for 20 minutes to an hour For example, elephant seals can dive to 1,500 m and
remain underwater for 2 hours
These animals have a high blood to body volume ratio
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Deep-diving air breathers can store large amounts of O2
Oxygen can be stored in their muscles in myoglobin proteins
Diving mammals also conserve oxygen by Changing their buoyancy to glide passively Decreasing blood supply to muscles Deriving ATP in muscles from fermentation once
oxygen is depleted
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Figure 34.UN02a
Plasma LDL cholesterol (mg/dL)
Perc
ent o
f ind
ivid
uals 30
20
10
03002502001501000
Individuals with an inactivating mutation in one copyof PCSK9 gene (study group)
50
© 2014 Pearson Education, Inc.
Figure 34.UN02b
Plasma LDL cholesterol (mg/dL)
Perc
ent o
f ind
ivid
uals 30
20
10
03002502001501000
Individuals with two functional copies of PCSK9 gene (control group)
50
© 2014 Pearson Education, Inc.
Figure 34.UN03
Alveolarepithelialcells
Pulmonaryarteries
Systemicveins
Pulmonaryveins
Systemicarteries
Systemiccapillaries
Alveolarcapillaries
Alveolarspaces
Exhaled air Inhaled air
Heart
Body tissue
CO2
CO2
O2
O2
© 2014 Pearson Education, Inc.
Figure 34.UN04
Fetus
PO2 (mm Hg)
O2 sa
tura
tion
ofhe
mog
lobi
n (%
)Mother
100806040200
100806040200
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