Transcript CO 2

Happy Thursday! 2/24/11
Explain the need for, and the mechanism of,
ventilation of the lungs in humans.
(Total 8 marks)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
8 max (Plus up to [2] for quality)
•Need:
•
draws fresh air / oxygen into the lungs;
•
removal / excretion of CO2;
•
maintains concentration gradient of O2 / CO2 / respiratory gases;
• Mechanism:
•
diaphragm contracts;
•
(external) intercostal muscles contract;
•
increased volume (of thorax / thoracic cavity);
•
decreasing air pressure in lungs;
•
air rushes in down air pressure gradient;
• converse of the above causes exhalation;
• abdominal muscles contract during active exhalation;
• elastic recoil of lungs helps exhalation;
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Chapter 22
Gas Exchange
PowerPoint Lectures for
Biology: Concepts and Connections, Fifth Edition
– Campbell, Reece, Taylor, and Simon
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Surviving in Thin Air
• Himalayas
– Have claimed many lives
• Air at height of world’s highest peak,
Mt. Everest
– Is so low in O2 : most
people would pass out
instantly if exposed to it!
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Twice a year, flocks of geese migrate over Himalayas
–
able to fly at such high altitude b/c lung efficiency
–
have hemoglobin w/very high affinity for oxygen
–
(Adaptation) carry lg amts oxygen to tissues, to
exchange with carbon dioxide
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• The process of gas exchange, often called
respiration
– interchange of O2 and CO2 between an
organism and its environment
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MECHANISMS OF GAS EXCHANGE
22.1 Overview: Gas exchange involves breathing,
transport of gases, and exchange of gases with tissue
cells
O2
1
CO2
Breathing
Lung
2
Circulatory
system
Transport
of gases by
the circulatory
system
Mitochondria
3
Figure 22.1
Exchange
of gases
with
body
cells
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CO2
Capillary
Cell
O2
• Gas exchange
– Provides O2 for cellular respiration and
– removes its waste product, CO2
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22.5 Terrestrial vertebrates have lungs
• In mammals, air inhaled through the nostrils
–
Passes through the pharynx and larynx into
& Smaller?
the trachea,
Smaller? and bronchioles
Air tube? bronchi,
Nasal
cavity
Pharynx
(Esophagus)
Larynx
Left lung
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
Figure 22.5A
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(Heart)
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Online Review Activity: Labeling Parts
• bronchioles end in clusters of tiny sacs called
alveoli
–
Oxygen-rich
blood
Where gasProcess?
exchange occurs
Oxygen-poor
blood
Alveoli
Blood
capillaries
Figure 22.5B, C
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Colorized SEM 6,200
Bronchiole
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CONNECTION
22.6 Smoking is a deadly assault on our
respiratory system
• Mucus
cilia in the respiratory passages
Structures,and
features?
– Protect the lungs
– Can be destroyed by smoking
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• Smoking
–
Causes lung cancer, heart disease, and
emphysema
Lung
Heart
Figure 22.6
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22.7 Breathing ventilates the lungs
• alternation of inhalation and exhalation
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Namesand
of muscles?
• The contraction of rib muscles
the diaphragm
–
Expands chest cavity, reduces air pressure in
alveoli (negative pressure breathing)
Air
inhaled
Rib cage
expands as
rib muscles
contract
Air
exhaled
Rib cage gets
smaller as
rib muscles
relax
Lung
Diaphragm
Diaphragm relaxes
(moves up)
Diaphragm contracts
(moves down)
Figure 22.7A
Inhalation
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Exhalation
read
last night? is the maximum volume of air
• Who
Vital
capacity
we can inhale and exhale
– But our lungs still hold a residual volume
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Air flows in one direction
– Through the more efficient lungs of birds!
Anterior
air sacs
Posterior
air sacs
Air
Air
Trachea
Lungs
Air
tubes
in lung
Inhalation:
Exhalation:
Air sacs fill
Air sacs empty; lungs fill
Figure 22.7B
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1 mm
22.9 Breathing is automatically controlled
• Breathing control centers in the brain
–
Keep breathing in tune with body needs, sensing
and responding to the COWhat
in the
blood
gas?
Where?
2 level
Brain
Cerebrospinal
fluid
Pons
Medulla
Breathing
control
centers
stimulated by:
Nerve signals
trigger
contraction
of muscles
CO2 increase /
pH decrease
in blood
CO2 and O2
sensors in
aorta
Diaphragm
Figure 22.8
Rib muscles
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Nerve signals
indicating CO2
and O2 levels
• A drop in blood pH
– Triggers an increase in rate & depth of
breathing
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TRANSPORT OF GASES IN THE BODY
22.9 Blood transports respiratory gases
• heart pumps O2 - poor blood to lungs
Where?
– picks up O2 , drops off CO2
Where?
• heart pumps O2 - rich blood to body
cells
– drops off O2 , picks up CO2
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Gas transport and exchange in the body
Inhaled air
Exhaled air
Alveolar
epithelial
cells
Air spaces
CO2
O2
Alveolar
capillaries of lung
CO2-rich,
O2-poor
blood
O2-rich,
CO2-poor
blood
Heart
Tissue
capillaries
CO2 Interstitial O2
fluid
Figure 22.9
Tissue cells
throughout body
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• Gases diffuse down partial-pressure gradients
– In the lungs and the tissues
Online Animation of Gas Exchange
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Molecule?
22.10 Hemoglobin
carries O2 and helps transport
CO2 and buffer the blood
Molecule?
• Hemoglobin
in red blood cells
–
Transports oxygen, helps buffer the blood
and carries some CO2
Iron atom
O2 loaded
in lungs
O2 unloaded
in tissues
Heme group
Figure 22.10
Polypeptide chain
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• Most CO2 in blood
CO2
Carbon
dioxide
–
transported as bicarbonate ions in plasma
+
H2O
Water
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H2CO3
Carbonic
acid
H+
Hydrogen
ions
+
HCO3–
Bicarbonate
CONNECTION
22.11 The human fetus exchanges gases with the
mother’s bloodstream
• In the
• placenta
Placenta, containing
maternal blood vessels
and fetal capillaries
Umbilical cord,
containing fetal
blood vessels
Amniotic
fluid
Uterus
Figure 22.11
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• Fetal hemoglobin
– Enhances oxygen transfer from maternal
blood
• At birth, increased CO2 in fetal blood
– Stimulates breathing control centers to
initiate breathing
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To be continued...(Reproduction Unit!)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
22.2 Animals exchange O2 and CO2 across moist
body surfaces
• Respiratory surfaces
– Must be thin and moist for diffusion of O2
and CO2 to occur
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• Some animals, like the earthworm
–
Use their entire skin as a gas-exchange organ
Cut
Cross
section
of respiratory
surface (the
skin covering
the body)
CO2
O2
Figure 22.2A
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Capillaries
• In most animals
–
Specialized body parts provide large
respiratory surfaces for gas exchange
Body surface
Body surface
Respiratory
surface
(gill)
CO2
Body cells
(no capillaries)
O2
CO2
Figure 22.2C
Capillary
O2
Body surface
Figure 22.2B
CO2
CO2
Figure 22.2D
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
O2
Respiratory
surface
(air tubes)
Respiratory
surface
(within lung)
O2
Capillary
22.3 Gills are adapted for gas exchange in
aquatic environments
• Gills are extensions of the body
– That absorb O2 dissolved in water
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• In a fish, gas exchange
– Is enhanced by ventilation and the
countercurrent flow of water and blood
Gill arch
Oxygen-poor
blood
Direction
of water flow
Lamella
Oxygen-rich
blood
Gill arch
15%
Blood
vessels
% O2 in water
flowing over
lamellae % O in blood
2
flowing through capillaries
Gill
in lamellae
filaments
Figure 22.3
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Countercurrent exchange
22.4 The tracheal system of insects provides
direct exchange between the air and body cells
• Land animals
– Exchange gases by breathing air
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• Tracheal systems in insects
–
Transport O2 directly to body cells through a
network of finely branched tubes
Air sacs
Tracheae
LM 250
Opening
for air
Body
cell
Tracheole
Air
sac
Trachea
Figure 22.4A, B
O2
CO2 Body wall
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings