copyright © 2009 pearson education, inc. people cannot survive in the air at the world’s highest...
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Copyright © 2009 Pearson Education, Inc.
People cannot survive in the air at the world’s highest peaks in the Himalayan Mountains
Twice a year, flocks of geese migrate over the Himalayas
How can geese fly where people cannot breathe?
Copyright © 2009 Pearson Education, Inc.
MECHANISMS OF GAS EXCHANGE
Copyright © 2009 Pearson Education, Inc.
Three phases of gas exchange1. Breathing2. Transport of oxygen and carbon dioxide in blood3. Body tissues take up oxygen and release
carbon dioxide
Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide
Lung
Exchangeof gaseswithbodycells
Cell
Capillary
Mitochondria
Breathing
Circulatorysystem
Transportof gases bythe circulatorysystem
CO2
CO2
O2
O21
2
3
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Respiratory surfaces must be thin and moist for diffusion of O2 and CO2
Cut
CO2
O2
Cross sectionof respiratorysurface (theouter skin)
CapillariesCO2
O2
Capillary
Body surface
Respiratorysurface(gill)
CO2 O2
Body surface
Capillary
Respiratorysurface(within lung)
O2CO2
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– Tetrapod adaptation: Fossil fish with legs had lungs and gills– Legs may have helped them lift up to gulp air– The fossil fish Tiktaalik illustrates these air-
breathing adaptations
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From the nasal cavity, air next passes to…
Left lung
Pharynx
Larynx
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
(Esophagus)
Nasalcavity
Oxygen-richblood
Bronchiole
Alveoli
Oxygen-poorblood
Bloodcapillaries
Nasalcavity
Left lung
Pharynx
Larynx
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
(Heart)
(Esophagus)
Oxygen-richblood
Bronchiole
Alveoli
Oxygen-poorblood
Bloodcapillaries
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Alveoli are well adapted for gas exchange
– High surface area of capillaries
– High surface area of alveoli
In alveoli– O2 diffuses into the
blood– CO2 diffuses out of
the blood
Oxygen-richblood
Bronchiole
Alveoli
Oxygen-poorblood
Bloodcapillaries
Why is smoking is a serious Why is smoking is a serious assault on the respiratory assault on the respiratory
system?system?
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1. Damages cilia and decreases mucus production in the respiratory passages
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1. Damages cilia and decreases mucus production in the respiratory passages
2. And also…– Increases the risk of heart attacks and
strokes (increases heart disease)– Raises blood pressure– Increases harmful types of cholesterol– Causes lung cancer (90%)– Causes emphysema
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Every year in the United States, smoking kills about 440,000 people
– This is more than all the deaths from accidents, alcohol, drug abuse, HIV, and murders combined
Adults who smoke cut 13–14 years from their lifespan
Lung
Heart
How is breathing How is breathing controlled?controlled?
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Breathing is usually under automatic control= breathing control center in brain
As CO2 increases (and pH decreases) in blood rate of depth of breathing
increases
Cerebrospinalfluid
Pons
Medulla
Brain
Nerve signalstrigger contractionof muscles
Diaphragm
Rib muscles
1
Cerebrospinalfluid
Pons
Medulla
Brain
Nerve signalstrigger contractionof muscles
Diaphragm
Rib muscles
1
Breathing controlcenters respondto pH of blood
2
Cerebrospinalfluid
Pons
Medulla
Brain
Nerve signalstrigger contractionof muscles
Diaphragm
Rib muscles
1
Breathing controlcenters respondto pH of blood
2
Nerve signalsindicating CO2
and O2 levels
3
CO2 and O2
sensors in aorta
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The heart pumps blood to two regions– The right side pumps oxygen-poor blood to the
lungs– The left side pumps oxygen-rich blood to the
body
In the lungs, blood picks up O2 and drops off CO2
In the body tissues, blood drops off O2 and picks up CO2
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Gases move from areas of higher concentration to areas of lower concentration
– Example: Gases in the alveoli of the lungs have more O2 and less CO2 than gases the blood
– How does this happen??
– Diffusion down the pressure gradient– Each gas exerts a pressure called partial
pressure
What physically carries the What physically carries the respiratory gasses in the respiratory gasses in the
blood?blood?
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Most animals transport O2 bound to proteins called respiratory pigments
– Iron-containing hemoglobin– Is used by almost all vertebrates and many
invertebrates– Transports oxygen, buffers blood, and transports
CO2
O2 loadedin lungs
O2 unloadedin tissues
Iron atom
Polypeptide chainHeme group
O2
O2
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◦ A human fetus– Does not breathe with its lungs
– Instead, it exchanges gases with maternal blood in the placenta
◦ In the placenta, capillaries of maternal blood and fetal blood run next to each other
– The fetus and mother do not share the same blood
Amnioticfluid
Uterus
Umbilical cord,containing fetalblood vessels
Placenta, containingmaternal blood vesselsand fetal capillaries