Chapter 22 Gas Exchange - Coach Shannon's Science Pagecoachshannon.weebly.com/uploads/3/0/1/1/30116035/... · 22.1 Overview: Gas exchange in an animal with lungs involves breathing,

Copyright © 2009 Pearson Education, Inc.

PowerPoint Lectures for

Biology: Concepts & Connections, Sixth Edition

Campbell, Reece, Taylor, Simon, and Dickey

Chapter 22 Gas Exchange

Lecture by Edward J. Zalisko


Introduction: Surviving in Thin Air

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?

– Geese have more efficient lungs than humans

– Geese hemoglobin has a very high affinity for oxygen


The process of gas exchange is called respiration, the interchange of

– O2 and the waste product CO2

– Between an organism and its environment

Introduction: Surviving in Thin Air


MECHANISMS OF GAS EXCHANGE


22.1 Overview: Gas exchange in an animal with lungs involves breathing, transport of gases, and exchange of gases with tissue cells

Three phases of gas exchange

– Breathing

– Transport of oxygen and carbon dioxide in blood

– 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


22.2 Animals exchange O2 and CO2 across moist body surfaces

Respiratory surfaces must be thin and moist for diffusion of O2 and CO2

Earthworms and other animals use their skin for gas exchange

Cut

CO2

O2

Cross section

of respiratory

surface (the

outer skin)

Capillaries


22.2 Animals exchange O2 and CO2 across moist body surfaces

Most animals have specialized body parts that promote gas exchange

– Gills in fish and amphibians

– Tracheal systems in arthropods

– Lungs in tetrapods that live on land

– Amphibians

– Reptiles

– Birds

– Mammals

CO2

O2

Capillary

Body surface

Respiratorysurface(gill)

CO2

O2

Body surface

Body cells(no capillaries)

Respiratorysurface(air tubes)

CO2 O2

Body surface

Capillary

Respiratorysurface(within lung)

O2CO2


22.3 Gills are adapted for gas exchange in aquatic environments

Gills

– Are extensions of the body

– Increase the surface to volume ratio

– Increase the surface area for gas exchange

– Oxygen absorbed

– Carbon dioxide released



In a fish, gas exchange is enhanced by

– Ventilation of the gills (moving water past the gills)

– Countercurrent flow of water and blood



Cold water holds more oxygen than warm water

Fresh water holds more oxygen than salt water

Turbulent water holds more oxygen than still water

Gillarch

Direction

of water

flow

Operculum

(gill cover)

Gillarch

Bloodvessels

Oxygen-richblood

Oxygen-poorblood

Lamella

Gillfilaments

Water flowbetweenlamellae

Blood flowthroughcapillariesin lamella

Countercurrent exchange

Blood flow in

simplified capillary,

showing % O2

Diffusion

of O2 from

water to

blood

Water flow, showing % O2

100 70 40 15

5306080

Gillarch

Direction

of water

flow

Operculum

(gill cover)

Gillarch

Bloodvessels

Oxygen-richblood

Oxygen-poorblood

Lamella

Gillfilaments

Water flowbetweenlamellae

Blood flowthroughcapillariesin lamella


Blood flow in


showing % O2

Diffusion

of O2 from

water to

blood


100 70 40 15

5306080

Gillarch

Directionof waterflow

Operculum(gill cover)

Gillarch

Bloodvessels

Gillfilaments

Gillarch

Blood

vessels

Oxygen-rich

blood

Oxygen-poor

blood

Lamella

Gill

filaments

Water flow

between

lamellae

Blood flow

through

capillaries in

lamella


Blood flow in


showing % O2

Diffusion

of O2 from

water to

blood


100 70 40 15

5306080


22.4 The tracheal system of insects provides direct exchange between the air and body cells

Compared to water, using air to breathe has two big advantages

– Air contains higher concentrations of O2

– Air is lighter and easier to move


22.4 The tracheal system of insects provides direct exchange between the air and body cells

Air-breathing animals lose water through their respiratory surfaces

Insect tracheal systems use tiny branching tubes

– This reduces water loss

– Air is piped directly to cells

TracheaeAir sacs

Openingfor air

Bodycell

TracheoleAirsac

Trachea

Body wallCO2O2


22.5 EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land

Tetrapods seem to have evolved in shallow water

– 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


22.5 EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land

The first tetrapods on land diverged into three major lineages

– Amphibians use small lungs and their body surfaces

– Nonbird reptiles have lower metabolic rates and simpler lungs

– Birds and mammals have higher metabolic rates and more complex lungs


22.6 In the human respiratory system, branching tubes convey air to lungs located in the chest cavity

In mammals, air is inhaled through the nostrils into the nasal cavity

– Air is filtered by hairs and mucus surfaces

– Air is warmed and moisturized

– Air is sampled for odors



From the nasal cavity, air next passes

– To the pharynx

– Then larynx, past the vocal cords

– Into the trachea, held open by cartilage rings

– Into the paired bronchi

– Into bronchioles

– And finally to the alveoli, grapelike clusters of air sacs, where gas exchange occurs

Oxygen-rich

blood

Bronchiole

Alveoli

Oxygen-poor

blood

Blood

capillaries

Nasalcavity

Left lung

Pharynx

Larynx

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

(Heart)

(Esophagus)

Left lung

Pharynx

Larynx

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

(Heart)

(Esophagus)

Nasalcavity

Oxygen-rich

blood

Bronchiole

Alveoli

Oxygen-poorblood

Bloodcapillaries



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


22.7 CONNECTION: Smoking is a serious assault on the respiratory system

Mucus and cilia in the respiratory passages

– Protect the lungs

– Can be damaged by smoking

Without healthy cilia, smokers must cough to clear dirty mucus from the trachea



Smoking can cause

– Lung cancer

– Heart disease

– Emphysema

Smoking accounts for 90% of all lung cancer cases

Smoking increases the risk of other types of cancer



Smoking also

– Increases the risk of heart attacks and strokes

– Raises blood pressure

– Increases harmful types of cholesterol

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


22.8 Negative pressure breathing ventilates our lungs

Breathing is the alternate inhalation and exhalation of air (ventilation)

Inhalation occurs when

– The rib cage expands

– The diaphragm moves downward

– The pressure around the lungs decreases

– And air is drawn into the respiratory tract



Exhalation occurs when

– The rib cage contracts

– The diaphragm moves upward

– The pressure around the lungs increases

– And air is forced out of the respiratory tract

Lung

Diaphragm contracts(moves down)

Diaphragm relaxes(moves up)

Diaphragm

Inhalation Exhalation

Airinhaled

Airexhaled

Rib cageexpands as

rib muscles

contract

Rib cage getssmaller asrib musclesrelax



Not all air is expelled during exhalation

– Some air still remains in the trachea, bronchi, bronchioles, and alveoli

– This remaining air is “dead air”

– Thus, inhalation mixes fresh air with dead air

One-way flow of air in birds reduces dead air and increases their ability to obtain oxygen


22.9 Breathing is automatically controlled

Breathing is usually under automatic control

Breathing control centers in the brain sense and respond to CO2 levels in the blood

A drop in blood pH increases the rate and depth of breathing

Cerebrospinalfluid

Pons

Medulla

Brain

Nerve signalstrigger contractionof muscles

Diaphragm

Rib muscles

1

Cerebrospinalfluid

Pons

Medulla

Brain


Diaphragm

Rib muscles

1

Breathing controlcenters respondto pH of blood

2

Cerebrospinalfluid

Pons

Medulla

Brain


Diaphragm

Rib muscles

1

Breathing controlcenters respondto pH of blood

2

Nerve signalsindicating CO2

and O2 levels

3

CO2 and O2

sensors in aorta


TRANSPORT OF GASES IN THE HUMAN BODY


22.10 Blood transports respiratory gases

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



Gases move from areas of higher concentration to areas of lower concentration

– Gases in the alveoli of the lungs have more O2 and less CO2 than gases the blood

– O2 moves from the alveoli of the lungs into the blood

– CO2 moves from the blood into the alveoli of the lungs

– The tissues have more CO2 and less O2 than in the blood

– CO2 moves from the tissues into the blood

– O2 moves from the blood into the tissues



Animation: CO2 from Blood to Lungs

Animation: CO2 from Tissues to Blood

Animation: O2 from Blood to Tissues

Animation: O2 from Lungs to Blood

22_10CO2BloodToLungs_A.html

22_10CO2BloodToLungs_A.html

22_10CO2TissuesToBlood_A.html

22_10CO2TissuesToBlood_A.html

22_10O2BloodToTissues_A.html

22_10O2BloodToTissues_A.html

22_10O2LungsToBlood_A.html

22_10O2LungsToBlood_A.html

Alveolar

epithelial

cells

CO2 O2

CO2-rich,

O2-poor

blood

O2-rich,

CO2-poor

blood

Exhaled air Inhaled air

Air spaces

Alveolarcapillaries

Tissuecapillaries

Tissue cellsthroughoutbody

Interstitialfluid

Heart

CO2 O2


22.11 Hemoglobin carries O2, helps transport CO2, and buffers the blood

Most animals transport O2 bound to proteins called respiratory pigments

– Copper-containing pigment is used by

– Molluscs

– Arthropods

– 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 chain

Heme group

O2

O2



Most CO2 in the blood is transported as bicarbonate ions in the plasma



+ - 2 2 2 3 3

Carbon Water Carbonic Hydrogen Bicarbonate Dioxide Acid Ions

CO + H O H CO H + HCO


22.12 CONNECTION: The human fetus exchanges gases with the mother’s bloodstream

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


22.12 CONNECTION: The human fetus exchanges gases with the mother’s bloodstream

Fetal hemoglobin

– Attracts O2 more strongly than adult hemoglobin

– Thus, fetal blood takes oxygen from maternal blood

At birth

– CO2 in fetal blood increases

– Breathing control centers initiate breathing

Amnioticfluid

Uterus

Umbilical cord,containing fetalblood vessels

Placenta, containingmaternal blood vesselsand fetal capillaries

Bloodflow

Water flow

Lamella

transport CO2 andbuffer the blood

tissue cells

regulated by

breathing controlcenters

mammalsventilate by

helpsto

andbinds andtransports

to transportgases between

red bloodcells contain

Gas exchange

requiresmoist, thin

oftenrelies on

for exchange of

neededfor

wasteproduct of

CO2O2

(e)

(d)(c)

(b)(a)

(g)(f)

a.

b.

c.

d.

e.

g.

f.

h.

P

Llama

Human

0

0

20

20

40

40 60

60

80

80 100

100

O2(mm Hg)


You should now be able to

1. Explain how geese can fly at altitudes higher than Mount Everest

2. Describe the three main phases of gas exchange in a human

3. Describe four types of respiratory surfaces and the types of animals that use them

4. Explain how breathing air compares to using water for gas exchange


You should now be able to

5. Describe the parts and functions of the human respiratory system

6. Describe the impact of smoking on human health

7. Explain how blood transports gases between the lungs and tissues of the body

8. Describe the functions of hemoglobin

9. Explain how a fetus obtains oxygen before and after birth

Documents

Chapter 22 Gas Exchange - Coach Shannon's Science Pagecoachshannon.weebly.com/uploads/3/0/1/1/30116035/... · 22.1 Overview: Gas exchange in an animal with lungs involves breathing,