AS CIE Gas exchange and smoking

H: Gas exchange and Smoking

1 Surface area:

1.1 Surface area and exchange surfaces

1.2 Surface area to volume ratio

1.3 Gas exchange surfaces

2 Gas exchange in human:

2.1 The human thorax

2.2 Gas exchange in the alveoli

2.3 Breathing = Ventilation

2.4 Lung capacity

2.4 Control of breathing in humans

2.5 Respiration and fitness

3 Smoking

4 Gas exchange in plants

5 Gas exchange in fish

6 Gas exchange in insects

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Xavier DANIEL, Ph.D. AS

All organisms respire

Respiration releases energy, needed for cell activities

movement, beating of heart and breathing movements

Oxygen + Glucose needed to release energy

Respiration that needs oxygen = aerobic respiration

Gas exchange: 1.Getting oxygen from environment

2. Releasing CO2 to environment

Humans: continous supply of air provided by ventilation mechanism = breathing

Specialized gas exchange surfaces = alveoli in the lungs

Large surface area + moist surface + thin wall

Increase rate of diffusion of :

1. oxygen into the blood

2. CO2 from the blood

Introduction


Introduction


Respiration Includes: • Pulmonary ventilation

– Air moves in and out of lungs

– Continuous replacement of gases in alveoli

• External respiration

– Gas exchange between blood and air at alveoli

– O2 in air diffuses into blood

– CO2 in blood diffuses into air

• Transport of respiratory gases (see lesson G1)

– Between the lungs and the cells of the body

– Performed by the cardiovascular system

– Blood is the transporting fluid

• Internal respiration

– Gas exchange in capillaries between blood and tissue cells

– O2 in blood diffuses into tissues

– CO2 waste in tissues diffuses into blood

Introduction


Cellular Respiration

• All body cells

• Oxygen is used by the cells

• O2 needed in conversion of glucose to cellular energy (ATP)

• Carbon dioxide is produced as a waste product

• The body’s cells die if either the respiratory or

cardiovascular system fails

Introduction


Countercurrent Exchange

• In a concurrent system,

equilibrium would be reached

at one end.

• Gas exchanges will stop

• Inefficient

• In a countercurrent system,

equilibrium is not reached

• Gas exchanges never stop

• Efficient

Introduction



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Surface area and exchange surfaces

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Exchange surface = surface to exchange materials between organism and environment Single-celled organsims: ES = outer membrane

Larger organisms: ES = specialized organs (lungs in mammals, gills in fish)

Gas exchange surfaces = ES for gas exchanges

Respiratory surface = GES for respiration

Surface area = amount of surface of an organism

Volume = space taken by an organism

Surface area to volume ratio influences how an organism gets O2 and releases CO2



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Surface area to volume ratio

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Small organisms Larger organisms


Surface area to volume ratio

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Negative correlation between

SAVR and Volume of cube

Gas exchanges

Large organisms have a large SAVR: body is not a cube, but flattened + enlarged extremities



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External GES

Internal GES


External Gas Exchange Surfaces 1

Aquatic single-celled organisms

Large SAVR

Use external surface for gas exchanges

Membrane is permeable to O2 and CO2

Concentration Water In the cell

Oxygen higher lower

Carbon dioxyde lower higher

Oxygen diffuses into the cell

CO2 diffuses out of the cell



Parasitic multicellular animals = Flatworms Intestinal parasites

Large SAVR


Body surface is permeable to O2 and CO2

Concentration Intestinal Tapeworm

liquid cells

Oxygen higher lower






Larger aquatic animals = Tadpoles and Lugworms

Smaller SAVR


Increase SAVR with presence of external gills

Larvae of amhibians

Concentration Water In the cell

Oxygen higher lower


Sandworms





Examples mentioned:

All gas exchanges happen between water or watery environment and cells

More efficient than exchange between air and cells

Why ?

Because oxygen and CO2 are more soluble in water than in air

Gas exchanges will always occur in watery environments

Mammalians: blood + wet inner surface of alveoli

Small organisms: transport inside the unique cell or to nearby cells by diffusion only

Bigger organisms: diffusion not enough

Need for internal gas exchange surfaces

Gills, Alveoli


Internal Gas Exchange Surfaces 1

Land organisms

External GES may

dry out

get physically damaged

Need for Internal GES

kept moist inside body

protected from damage

High metabolism: need large GES

+ Need for transportation system

Internal folded membranes

Alveoli of mammals

Internal gills of fish

GES increased

Gases only diffuse through

water-permeable membranes !

Loss of water to dry environment reduced

By a dry, waterproof outer layer Human skin, chitinous exoskeleton arthropods, waxy cuticle plants


External/Internal Gas Exchange Surfaces 1

Mature Frogs have

internals lungs

Tadpoles have

External gills

???


Features of Gas Exchange Surfaces 1

GES used for Respiration and Photoynthesis

For efficient gas exchange, GES must

Be THIN Have a Large

surface area

Be MOIST Be close to a

transportation system

Use a

Ventilation system

Folded GES Permeable

to gases

O2 and CO2 only diffuse through

water-permeable membranes !

Faster

diffusion Reach cells

not close to GES

Constantly renew

air/water

in contact with GES



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2 The Human Thorax


The Respiratory System

2 The Human Thorax


1. Trachea (the windpipe)

16-20 C-shaped rings of cartilage

joined by fibroelastic connective tissue

Flexible for bending

But stays open during breathing

2. Trachea divides into two

primary bronchi (bronchus if singular)

Enter the lungs

3. Bronchi divide into bronchioles

End in alveolar sacs

4. Alveolar sacs are made of alveoli

(alveolus if singular)

Gas exchanges between air and blood

300 million per human lung

The Lower Respiratory Tract

2 The Human Thorax

Bronchi and largest bronchioles

have cartilage rings too


The Trachea

2 The Human Thorax

Cilia

H: cilia

I: columnar cells

J: Goblet cells

Dirt and bacteria trapped in mucus

Cilia move up mucus to mouth

Swallowed

Destroyed in stomach (pH 2)

Same as in bronchi

and bronchioles


27

Lungs Cone-shaped with

anterior, lateral and posterior

surfaces contacting ribs

Superior tip is apex,

just deep to clavicle

Concave inferior surface

resting on diaphragm is

the base

apex apex

base base

The Respiratory System

2 The Human Thorax


• Pulmonary arteries bring oxygen-poor blood to the lungs – Branch along with the bronchial tree

– The smallest feed into the pulmonary capillary network around the alveoli

• Pulmonary veins carry oxygenated blood from the alveoli to the heart

2 The Human Thorax

Oxygen transport by blood in lungs

Bronchial tree



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Gas Exchange in the alveoli 2


• Site of gas exchange

• Moist

Surfactant fluid on inner surface

• Thin-walled: one cell thick (0.5 mm)

• Direct contact with capillary

• Distance for gas to cross = 2 cells only

Blood comes

Blood leaves


Gas exchange possible

Gas exchange faster


• The respiratory surface is made up

of the alveoli and capillary walls

• The walls of the capillaries and the

alveoli may share the same

membrane

• Blood flow is continuous

1. [O2]blood kept lower than [O2]air

O2 keeps diffusing from air to blood by

simple diffusion

2. [CO2]blood kept higher than [CO2]air

CO2 keeps diffusing from blood to air by

simple diffusion




At rest: Ventilation brings fresh supply of air

12 times per minute

Tidal air = inspired air

Does not fill the whole alveoli air space

Not all air in alveoli is replaced

Remaining air = alveolar air

Ventilation is continuous

1. [O2]alveolar air kept lower than [O2]tidal air

O2 keeps diffusing from tidal air to alveolar air by simple diffusion

2. [CO2]tidal air kept higher than [CO2]alveolar air

CO2 keeps diffusing from alveolar air to tidal air by simple diffusion



Gas % Tidal air Alveolar air Expired air

(volume) (inspired)

Oxygen 20.7 % 13.2 % 14.5%

Carbon dioxide 0.04 % 5 % 3.9 %

Nitrogen 78 % 75.6 % 75.4 %

Water vapour 1.26 % 6.2 % 6.2 %



Gas % Tidal air Alveolar air Expired air

(volume) (inspired)

Oxygen 20.7 % 13.2 % 14.5%

Carbon dioxide 0.04 % 5 % 3.9 %

Nitrogen 78 % 75.6 % 75.4 %

Water vapour 1.26 % 6.2 % 6.2 %


1. Most oxygen and least carbon dioxide: Tidal air

2. More oxygen and less carbon dioxide: Alveolar air

3. Least oxygen and most carbon dioxide: Blood from the

pulmonary

arteries


O2

O2

CO2

CO2



A

B

C


Haemoglobin

=

Respiratory pigment

Oxygen exchange in the alveoli 2


Carbon dioxide exchange in the alveoli 2

Plasma

Haemoglobin


Carbon dioxide exchange in the alveoli 2

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Oxygen and Carbon dioxide exchange in the alveoli 2


• Why use a carrier molecule?

– O2 not soluble enough in H2O for animal needs

• blood alone could not provide enough O2 to animal cells

• haemocyanin in insects = copper (bluish/greenish)

• haemoglobin in vertebrates = iron (reddish)

• Reversibly binds O2

– loading O2 at lungs or gills & unloading at cells

cooperativity

haeme group

Haemoglobin 2


Lungs Hb + O2 gives HbO2 Oxyhaemoglobin

High partial Pressure O2

High affinity of Hb for O2

Maximum take up O2 from air

Respiring tissues HbO2 gives Hb + O2 Deoxyhaemoglobin

Low partial Pressure O2

Low affinity of Hb for O2

Maximum release O2 to tissues

Haemoglobin dissociation curve

Each oxygen that binds to Hb increases the attraction of Hb for the next oxygen

The curve is then sigmoid

Haemoglobin 2


Affinity of Haemoglobin for Oxygen can vary

Haemoglobin 2


Affinity of different Globins for Oxygen varies

highest

high

lowest

Haemoglobin 2


Affinity of Haemoglobin for Oxygen can vary

Haemoglobin 2


Increased carbon dioxide in the

blood causes a right-shift in the

curves

Affinity of Hb for O2 decreases

Haemoglobin more easily

unloads the oxygen it is

carrying.

Haemoglobin and The Bohr effect 2



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• Two phases – Inspiration (inhalation) – air in

– Expiration (exhalation) – air out

• Mechanical forces cause the movement of air – Gases flow from higher pressure to lower

– Air enters the thorax because the pressure of the air in it is lower than the atmospheric pressure

• Making the volume of the thorax larger means the air inside it is

under less pressure

• The diaphragm and intercostal muscles accomplish this

Breathing = Ventilation 2


Muscles of active Inspiration

• The dome-shaped diaphragm contracts and flattens

– Increases the height of the thoracic cavity

• The external intercostal muscles contract to move the ribs up and out

– Increases the circumference of the thoracic cavity


• Thorax volume increases

• Thorax pressure decreases

• Thorax pressure becomes lower than atmospheric pressure

• Air is sucked in


• The flattened diaphragm relaxes and becomes dome-shaped again

– Decreases the height of the thoracic cavity

• The external intercostal muscles relax,

moving the ribs down and in

– Decreases the circumference of the thoracic cavity


• Thorax volume decreases

• Thorax pressure increases

• Thorax pressure becomes higher than atmospheric pressure

• Air is forced out

Normal, passive Expiration

Lungs and chest walls

are elastic

Elastic recoil

Helps push air out


Negative pressure breathing


Volume increases

Pressure decreases

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Volume increases 2

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Pressure decreases 3

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– Contraction of abdominal wall muscles

– Increases intra-abdominal pressure, forcing the diaphragm up

– Depressing the rib cage, decreases thoracic volume even more

(try this on yourself to feel the different muscles acting)

Forced, active Expiration




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Measurement of Lung Capacity Use a Spirometer to get a spirogram

Lung Capacity 2


Lung Capacity 2

Tidal volume: volume of air inhaled and exhaled in a single breath

Residual volume: air that remains in the airways, does not participate in gas exchange

Vital capacity: maximal volume that can be exhaled after maximal inhalation and forced exhalation

500 cm3

3000

to

5000 cm3

1500 cm3


Lung Capacity 2

Inspiratory reserve volume: amount of air that can be inhaled beyond TV

Expiratory reserve volume: amount of air that can be forcibly exhaled beyond TV

Total lung capacity = IRV +TV + ERV + RV

3000 cm3

1000 cm3

3500

to

8000 cm3


Lung Capacity 2

Functional residual capacity = ERV + RV volume of air present in the lungs at the end of passive expiration

Inspiratory capacity = TV + IRV maximum volume of air that can be inhaled


Tidal volume: volume of air inhaled and exhaled in a single breath

Residual volume: air that remains in the airways and does not participate in gas exchange

Vital capacity: maximal volume that can be exhaled after maximal inhalation

Inspiratory reserve volume: amount of air that can be inhaled beyond the tidal volume

Expiratory reserve volume: amount of air that can be forcibly exhaled beyond the tidal volume

Total lung capacity = IRV +TV + ERV + RV

Functional residual capacity = ER + RV

volume of air present in the lungs at the end of passive expiration

Inspiratory capacity = TV + IRV

maximum volume of air that can be inhaled

Lung Capacity 2



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Goal of breathing = Supply oxygen to tissues that need it

Needs in O2 depends on activity

Breathing must be regulated to fit these needs

Respiratory center in the medulla

Sends signals to diaphragm and external intercostal muscles

Contract or relax

Control of Breathing in Humans 2

Medulla sets the rhythm Pons regulates the rhythm Xavier DANIEL, Ph.D. AS

Control of Breathing in Humans 2

Chemoreceptors: sensitive to CO2

Receptors sense their specific stimulus, then send message to medulla to trigger response

Stretch receptors: sensitive extent of lung inflation

Wall of bronchi



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Respiration and Fitness 2

Respiration = process to release energy = ATP from organic molecules

Respiration takes place in every living cell

More active cells: respire faster, produce more energy

Exercise: breathing rate increases to supply more O2 for more respiration

Aerobic respiration

Requires oxygen In mitochondria

Efficient: 1 glucose used, 38 ATP produced

Anaerobic respiration

When supply of oxygen is not enough

Inefficient: 1 glucose used, 2 ATP produced

Remaining energy trapped in ethanol (plants) or lactate (animals)

Animals: cramps due to accumulation of lactate in muscles

Rubbing cramped muscles to increase blood flow: remove lactate and bring more O2


Respiration and Fitness 2

Fit and active athletes: larger vital capacity

Can provide more O2 to make sure anaerobic respiration does not take place fast

Increased size of blood vessels irrigating muscles

Muscles’ size increases

Roger Federer

Normal breathing: 12 times per minute 60 000 cm3 air

Fit female athletes: 12 times per minute 70 000 cm3 air

Fit male athletes: 12 times per minute 100 000 cm3 air

Sustained exercise makes coronary ateries wider

Risks of coronary thrombosis decreases



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Effects of smoking

Inhaled smoke contains:

• CO2 that affects the

CO2 diffusion

gradient.

• Carcinogenic

chemicals that can

trigger tumors.

• Toxic nicotine, which

paralyzes cilia and

creates addiction

Smoking 3


Lung cancer

• Most common cancer in males: 21% of all cancers

• Second common cancer in females: 12% of all cancers

• Cancer caused by carcinogens

• Cancerous tumors usually develop in bronchial tubes

• May spread to invade other tissues (metastases)

• TAR:

– irritates epithelial cells

– stimulates extra cell division

– thickened epithelium

– may develop into cancerous tumor

Smoking 3


Chronic bronchitis

• Tar deposits on lining epithelium of breathing vessels

• Irritation + Production of excess mucus from goblet cells

• Cilia paralyzed

• Bacteria + dirt trapped in mucus: chances of infection

increase (pneumonia)

• Smoker coughs to try and get rid of excess mucus

– Further damages epithelium: inflammation, bronchial tubes narrow

– Can lead to emphysema

Smoking 3


Emphysema • Smoking stimulates

secretion of proteases

• Target = elastin in alveolar

walls

• Air space increases

• GES decreases

• Breathing less efficient

• Consequences: lack of

energy + breathlessness

• Coughing may break some

weakened alveoli

Smoking 3


Coronary heart disease and strokes

Nicotine

• Diffuses into blood

• Increases blood pressure, heart rate

• Narrows blood vessels

• Nicotine and CO2

– Both damage epithelium of blood vessels

– Fat and cholesterol enter blood vessels more easily

– Atherosclerosis

– May lead to heart attack and/or strokes

Smoking 3


you might want to think twice about smoking….

Smoking 3


Links Between Smoking and Disease Two groups of links:

Epidemiological evidence looks for patterns in the diseases, which smokers suffer from. It

only shows an association and not a causal link.

Experimental evidence attempts to prove a causal link.

Chronic obstructive pulmonary disease is very rare in non-smokers and 90% of deaths from it

can be attributed to smoking.

98% of people with emphysema smoke and 20% of smokers suffer from it.

Deaths from pneumonia and influenza are twice as high among smokers.

Lung cancer is eighteen times more likely in smokers and one third of all cancer deaths can be

attributed to smoking.

25% of smokers die from lung cancer and the risks are higher if they inhale, start young,

smoke a large number of cigarettes a day and smoke over a long period of time.

Smoking 3


Links Between Smoking and Disease

The risks of developing lung cancer fall as soon as smoking stops but it takes ten years for the

risks to fall to that of a non-smoker.

Experimental evidence includes the development of tumours in animals exposed to smoke and

the identification of carcinogens in tar.

Both lung cancer and chronic obstructive lung disease have been observed in dogs and tar has

caused cancerous growths in the skin of mice.

Smoking 3


“Two lies and a truth” – which one is true?

1 2 3

33% 33%33%1. Cigarette smoke cures

colds because it kills

bacteria in the lungs.

2. Nicotine is one of the

most potent

neurotoxins on earth.

3. “Passive” smoking is

less harmful than

“regular” smoking.

Smoking 3



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Gas exchange in Plants 4


Gas exchange in Plants 4

Different plants, different habitats, different amounts of water available

Mode of gas exchange depends on habitats

Three main types

Mesophytes Xerophytes Hydrophytes

Land plants

Water not short supply

No special adaptation

to reduce water loss

Land plants

Water in short supply

(soil and air)

Absorption by roots difficut

Transpiration must be minimised

Highly special adaptation


Plants on or in fresh water

Water in high supply

No special adaptation


“moderate”


Gas exchange in Mesophytes 4

Gas exchange needed for Photosynthesis, Respiration and Transpiration

Places of gas exchange = mostly somata and lenticels

Main GES = spongy mesophyll in leaves

Cells coated with layer water

Gas can dissolve in that layer

Gas exchange possible

Cells loosely packed

Surface area for gas exchange increased

Thin cell walls

Diffusion of gases faster



Air enters via stomata

No ventilation process

Night Only respiration (O2 needed, CO2 produced), no Photosynthesis

O2 enters via stomata

O2 transported down gradient by diffusion from spongy mesophyll to all tissues

[O2] in spongy mesophyll stays lower than in leaf air space

Continuous transport (air, leaf air space, spongy mesophyll, tissues)

CO2 transported down gradient by diffusion from all tissues to spongy mesophyll

[CO2] in spongy mesophyll stays higher than in leaf air space

Continuous transport (tissues, spongy mesophyll, leaf air space, air)

CO2 gets out via stomata

All O2 comes from air



Day Respiration (O2 needed, CO2 produced)

+

Photosynthesis (O2 and water produced , CO2 needed)

O2 enters via stomata

O2 transported down gradient by diffusion from spongy mesophyll to all tissues

[O2] in spongy mesophyll stays lower than in leaf air space

Continuous transport (air, leaf air space, spongy mesophyll, tissues)

CO2 transported down gradient by diffusion from all tissues to spongy mesophyll

[CO2] in spongy mesophyll stays higher than in leaf air space

Continuous transport (tissues, spongy mesophyll, leaf air space, air)

CO2 gets out via stomata

Some CO2 is kept for Photosynthesis

Some O2 comes from air,

some from palisade cells

Some CO2 comes from air,

some from palisade cells



Day with bright light Respiration (O2 needed, CO2 produced)

+


CO2 needed more than respiration provides

Palisade cells perform photosynthesis, using CO2

[CO2] in palisade cells lower than leaf air space

[CO2] in leaf air space higher than spongy mesophyl cells

[CO2] concentration gradient: LAS > SMC > PC

CO2 diffuses from LAS to SMC, then to palisade cells

Continuous transport (air, leaf air space, spongy mesophyl, palisade cells)

Not enough

Some CO2 is taken from atmosphere



Day with bright light Respiration (O2 needed, CO2 produced)

+


Palisade cells perform photosynthesis, producing O2

[O2] in palisade cells higher than spongy mesophyl cells

[O2] in spongy mesophyl cells higher than leaf air space

[O2] concentration gradient: PC > SMC > LAF

O2 diffuses from PC to SMC, then to LAF

Continuous transport (palisade cells, spongy mesophyl, leaf air space, air)

More than enough

Extra O2 is released in the atmosphere

Life is possible on earth for breathing organisms


Gas exchange in Xerophytes 4

Xerophytes

Xero = dry phuton = plant

Plants adapted to dry conditions: low rains, dry/salty soils, hot winds

Extensive root system: to take up water

Storing of solutes in roots: to lower the root’s Ψ

Swollen stems: to store water

Thick waxy cuticle: to reduce transpiration

Curled or thorn-like leaves: to reduce transpiration

Sunken stomata: to reduce transpiration

Photosynthesis

and Respiration

less efficient


Gas exchange in Hydrophytes 4

Live in fresh water

Have adapted to this environment

No risk of dehydration

Little or no waxy cuticle

Water provides support + allows constant turgidity

Xylem poorly developed



Hydrophytes with floating leaves Duckweed, water lilies

Most stomata on upper surface of leaves

Air is much richer in O2 and CO2 than water

Spongy mesophyl = GES kept moist

Diffusion of gases fast

No risk of dehydration

Hydrophytes with submerged roots Water lilies, water crowfoot

Not enough O2 in water for aerobic transpiration

Aerenchymas: transport of O2 from

aerial parts to roots

Duckweed

Water lilies

Water crowfoot



What about rice ?



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Gas exchange in Fish 5


Gills


• 3–7 gill arches on each side

of a fish’s head

• Gill arch: two rows of gill filaments

• Gill filament made of lamellae = GES

Thin and large surface Xavier DANIEL, Ph.D. AS


1. Mouth opens: volume increases

pressure decreases

water enters

2. Mouth closes: volume decreases

pressure increases

Water cannot go out through

mouth because of valves

Water forced out through

operculum

To gills and their lamellae


• In lamella, blood flows opposite

to water movement

– Countercurrent flow

– Increases concentration gradients (O2 and CO2)

– Maximizes gas exchanges

• Fish gills are the most efficient

of all respiratory organs




Countercurrent flow • Water has always more available oxygen than the blood

• Oxygen diffusion continuelly takes place

(even after the blood has acquired more than 50% of the water's oxygen)

• The system gives fish an 80-90% efficiency in acquiring oxygen



Countercurrent flow



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Terrestrial arthropods = Insects

Land organisms

Water loss minimised by chitinous exoskeleton

Need moist, internal GES

Gas exchange in Insects



• Respiratory system:

Air ducts = trachea

Rings of chitin

Impermeable to gases

Trachea branch into smaller tracheoles

– Tracheoles: direct contact with muscle cells

– Permeable to gases

– GES – exchange gases with cells

– Heomolymph not used for gas echanges in insects

– Spiracles = openings in the exoskeleton

opened or closed by valves Xavier DANIEL, Ph.D. AS

• air tubes branching throughout body

• gas exchanged by diffusion across

moist cells lining terminal ends, not

through open circulatory system

Tracheae




Ventilation system in locust and grasshoppers

Rhythmic expansion / contraction of thorax + abdomen


Gas exchange in many forms…

one-celled amphibians echinoderms

insects fish mammals


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AS CIE Gas exchange and smoking