Animal Circulation and Gas Exchange Systems Overview

1

Lecture #11 – Animal Circulation

and Gas Exchange Systems

2

Key Concepts:

•

Circulation and gas exchange – why?

•

Circulation – spanning diversity

•

Hearts – the evolution of double circulation

•

Blood circulation and capillary exchange

•

Blood structure and function

•

Gas exchange – spanning diversity

•

Breathing – spanning diversity

•

Respiratory pigments

3

Animals use O

2

 and produce CO

2

•

All animals are aerobic



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

Some animals use lots of oxygen to maintain

body temperature

•

All animals produce CO

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 as  a byproduct of

aerobic respiration

•

Gasses must be exchanged



Oxygen must be acquired from the environment



Carbon dioxide must be released to the

environment

4

Except……breaking news!

http://www.biomedcentral.com/1741-7007/8/30

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This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments.

Our findings allow us also to conclude that these metazoans live under anoxic conditions through an

obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes.

The discovery of these life forms opens new perspectives for the study of metazoan life in habitats

lacking molecular oxygen.

5

Animals use O

2

 and produce CO

2

•

Circulation systems move gasses (and other

essential resources such as nutrients,

hormones, etc) throughout the animal’s

body

•

Respiratory systems exchange gasses with

the environment

6

Circulation systems have evolved

over time

•

The most primitive animals exchange

gasses and circulate resources entirely by

diffusion



Process is slow and cannot support 3-D large

bodies

•

Sponges, jellies and flatworms use diffusion

alone

7

Critical Thinking

•

Why isn’t diffusion adequate for exchange

in a 3D large animal???

8

Critical Thinking

•

Why isn’t diffusion adequate for exchange

in a 3D large animal???

9

Critical Thinking

•

But…..plants rely on

diffusion for gas

exchange…..how do

they get so big???

10

Critical Thinking

•

But…..plants rely on

diffusion for gas

exchange…..how do

they get so big???

11

Circulation systems have evolved

over time

•

The most primitive animals exchange

gasses and circulate resources entirely by

diffusion



Process is slow and cannot support 3-D large

bodies



Surface area / volume ratio becomes too small

•

Sponges, jellies and flatworms use diffusion

alone

12

Diagram of sponge structure

Virtually every cell in a sponge is in direct

contact with the water – little circulation is

required

13

Diagram of jellyfish structure, and photos

•

Jellies and flatworms have thin bodies and

elaborately branched gastrovascular cavities



Again, all cells are very close to the external

environment



This facilitates diffusion



Some contractions help circulate (contractile

fibers in jellies, muscles in flatworms)

14

Diagram of open

circulatory system in a

grasshopper

Circulation systems have evolved

over time



Metabolic energy is

used to pump

hemolymph through

blood vessels into the

body cavity



Hemolymph is returned

to vessels via ostia –

pores that draw in the

fluid as the heart

relaxes

•

Most invertebrates (esp. insects) have an

open circulatory system

15

Diagram of a closed

circulatory system, plus

a diagram showing an

earthworm circulatory

system

Circulation systems have evolved

over time



Metabolic energy is

used to pump blood

through blood vessels



Blood is contained

within the vessels



Exchange occurs by

diffusion in capillary

beds

•

Closed circulatory systems separate blood

from interstitial fluid

16

Open vs. Closed…both systems

are common

Open systems….

•

Use less metabolic

energy to run

•

Use less metabolic

energy to build

•

Can function as a

hydrostatic skeleton

•

Most invertebrates

(except earthworms

and larger mollusks)

have open systems

Closed systems….

•

Maintain higher

pressure

•

Are more effective at

transport

•

Supply more oxygen

to support larger and

more active animals

•

All vertebrates have

closed systems

17

All vertebrates have a closed

circulatory system

•

Chambered heart pumps blood



Atria receive blood



Ventricles pump blood

•

Vessels contain the blood



Veins carry blood to atria



Arteries carry blood from ventricles

•

Capillary beds facilitate exchange



Capillary beds separate arteries from veins



Highly branched and very tiny



Infiltrate all tissues in the body

We’ll go over these

step by step

18

Diagram of a chambered heart

Chambered heart pumps blood

•

Atria receive blood

•

Ventricles pump

blood

•

One-way valves

direct blood flow

19

Critical Thinking

•

Atria receive blood; ventricles pump

•

Given that function, what structure would

you predict???

20

Critical Thinking

•

Atria receive blood; ventricles pump

•

Given that function, what structure would

you predict???

21

Diagram of a chambered heart

Chambered heart pumps blood

•

Atria receive blood



Soft walled, flexible

•

Ventricles pump

blood



Thick, muscular

walls

•

One-way valves

direct blood flow

22

Diagram showing

artery, vein and

capillary bed

Vessels contain the blood

•

Arteries carry blood

from

 ventricles



Always under pressure

•

Veins carry blood 

to

atria



One-way valves

prevent back flow



Body movements

increase circulation



Pressure is always low

23

Diagram of blood

circulation pattern

in humans

Note that blood vessel names reflect the

direction of flow, NOT the amount of

oxygen in the blood

•

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

Arterial blood is always

under pressure



It is NOT always

oxygenated

•

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24

Diagram showing

artery, vein and

capillary bed

Capillary beds facilitate exchange

•

Capillary beds separate arteries from veins

•

Highly branched and very tiny

•

Infiltrate all tissues in the body

•

More later

25

All vertebrates have a closed

circulatory system – REVIEW

•

Chambered heart pumps blood



Atria receive blood



Ventricles pump blood

•

Vessels contain the blood



Veins carry blood to atria



Arteries carry blood from ventricles

•

Capillary beds facilitate exchange



Capillary beds separate arteries from veins



Highly branched and very tiny



Infiltrate all tissues in the body

26

Diagram showing progression from a 1-

chambered heart to a 4-chambered heart.

This diagram is used in the next 12 slides.

Evolution of double circulation –

not all animals have a 4-chambered heart

27

Fishes have a 2-chambered heart

•

One atrium, one ventricle

•

A single pump of the heart

circulates blood through 2

capillary beds in a single circuit



Blood pressure drops as blood

enters the capillaries (increase in

cross-sectional area of vessels)



Blood flow to systemic capillaries

and back to the heart is very slow



Flow is increased by swimming

movements

28

Two circuits increases the efficiency of

gas exchange = double circulation

•

One circuit goes to exchange surface

•

One circuit goes to body systems

•

Both under high pressure – increases flow rate

29

Amphibians have a 3-chambered heart

•

Two atria, one ventricle

•

Ventricle pumps to 2 circuits



One circuit goes to lungs and skin

to release CO

2

 and acquire O

2



The other circulates through body

tissues

•

Oxygen rich and oxygen poor

blood mix in the ventricle



A ridge helps to direct flow

•

Second pump increases the

speed of O

2

 delivery to the body

30

Most reptiles also have a 3-chambered

heart

•

A partial septum further

separates the blood flow and

decreases mixing



Crocodilians have a complete

septum

•

Point of interest: reptiles have

two arteries that lead to the

systemic circuits



Arterial valves help direct blood

flow away from pulmonary circuit

when animal is submerged

31

Critical Thinking

•

What is a disadvantage of a 3 chambered

heart???

32

Critical Thinking

•

What is a disadvantage of a 3 chambered

heart???

33

Mammals and birds have

4-chambered hearts

•

Two atria and two ventricles

•

Oxygen rich blood is completely

separated from oxygen poor blood



No mixing 



 much more efficient

gas transport



Efficient gas transport is essential

for both movement and support of

endothermy



Endotherms use 10-30x more

energy to maintain body

temperatures

34

Mammals and birds have

4-chambered hearts

•

Mammals and birds are NOT

monophyletic

•

What does this mean???

35

Phylogenetic tree showing

the diversification of

vertebrates

Mammals and birds have

4-chambered hearts

•

Mammals and birds are NOT monophyletic

36

Mammals and birds have

4-chambered hearts

•

Mammals and birds are NOT

monophyletic

•

Four-chambered hearts evolved

independently

•

What’s this called???

37

Mammals and birds have

4-chambered hearts

•

Mammals and birds are NOT

monophyletic

•

Four-chambered hearts evolved

independently

38

Review: evolution of double circulation

39

Blood Circulation

•

Blood vessels are organs



Outer layer is elastic connective tissue



Middle layer is smooth muscle and elastic

fibers



Inner layer is endothelial tissue

•

Arteries have thicker walls

•

Capillaries have only an endothelium and

basement membrane

40

Critical Thinking

•

Arteries have thicker walls than veins

•

Capillaries have only an endothelium and

basement membrane

•

What is the functional significance of this

structural difference???

41

Critical Thinking

•

Arteries have thicker walls than veins

•

Capillaries have only an endothelium and

basement membrane

•

What is the functional significance of this

structural difference???

42

Diagram showing

artery, vein and

capillary bed

Form reflects function…

•

Arteries are

under more

pressure than

veins

•

Capillaries are

the exchange

surface

43

Graph showing relationships

between blood pressure,

blood velocity, and the cross-

sectional area of different

kinds of blood vessels –

arteries to capillaries to

veins.  This same graph is

on the next 3 slides.

Blood

pressure

and velocity

drop as

blood moves

through

capillaries

44

Total cross-

sectional area

in capillary

beds is much

higher than in

arteries or

veins; slows

flow

45

Velocity

increases as

blood passes

into veins

(smaller cross-

sectional

area);

pressure

remains

dissipated

46

One-way

valves and

body

movements

force blood

back to right

heart atrium

47

Critical Thinking

•

What makes rivers curl on the Coastal

Plain???

48

Critical Thinking

•

What makes rivers curl on the Coastal

Plain???

49

Emphasize the

difference

between velocity

and pressure!!!

Velocity

increases in the

venous system;

pressure does

NOT

50

Capillary Exchange

•

Gas exchange and other transfers occur in

the capillary beds

•

Muscle contractions determine which beds

are “open”



Brain, heart, kidneys and liver are generally

always fully open



Digestive system capillaries open after a meal



Skeletal muscle capillaries open during

exercise



etc…

51

Diagram showing

sphincter muscle

control over

capillary flow.

Micrograph of a

capillary bed.

Bed fully open

Bed closed, through-

flow only

Note scale – capillaries

are very tiny!!

52

Capillary Transport Processes:

•

Endocytosis 



exocytosis across membrane

•

Diffusion based on electrochemical gradients

•

Bulk flow between endothelial cells



Water potential gradient forces solution out at

arterial end



Reduction in pressure draws most (85%) fluid

back in at venous end



Remaining fluid is absorbed into lymph, returned

at shoulder ducts

53

Capillary Transport Processes:

•

Endocytosis 



exocytosis across membrane

•

Diffusion based on concentration gradients

•

Bulk flow between endothelial cells



Water potential gradient forces solution out at

arterial end



Reduction in pressure draws most (85%) fluid

back in at venous end



Remaining fluid is absorbed into lymph, returned

at shoulder ducts

54

Bulk Flow in Capillary Beds

•

Remember water potential: 

Ψ

 = P – s

•

Remember that in bulk flow P is dominant



No membrane



Plus, in the capillaries, s is ~stable (blood

proteins too big to pass)

•

P changes due to the interaction between

arterial pressure and the increase in cross-

sectional area

55

Diagram showing osmotic changes across a capillary bed

Bulk Flow in Capillary Beds

Remember: 

Ψ

 = P – s

56

Capillary Transport Processes:

•

Endocytosis 



exocytosis across membrane

•

Diffusion based on concentration gradients

•

Bulk flow between endothelial cells



Water potential gradient forces solution out at

arterial end



Reduction in pressure draws most (85%) fluid

back in at venous end



Remaining fluid is absorbed into lymph, returned

at shoulder ducts

57

Blood structure and function

•

Blood is ~55% plasma and ~45% cellular

elements



Plasma is ~90% water



Cellular elements include red blood cells, white

blood cells and platelets

58

Chart listing all blood components – both liquid and cellular

Blood Components

59

Plasma Solutes 

– 10% of plasma volume

•

Solutes



Inorganic salts that maintain osmotic balance, buffer pH

to 7.4, contribute to nerve and muscle function



Concentration is maintained by kidneys

•

Proteins



Also help maintain osmotic balance and pH



Escort lipids (remember, lipids are insoluble in water)



Defend against pathogens (antibodies)



Assist with blood clotting

•

Materials being transported



Nutrients



Hormones



Respiratory gasses



Waste products from metabolism

60

Cellular Elements

•

Red blood cells, white blood cells and

platelets



Red blood cells carry O

2

 and some CO

2



White blood cells defend against pathogens



Platelets promote clotting

61

Red Blood Cells

•

Most numerous of all blood cells

•

5-6 million per mm

3

 of blood!

•

25 trillion in the human body

•

Biconcave shape

•

No nucleus, no mitochondria



They don’t use up any of the oxygen they carry!

•

250 million molecules of hemoglobin per cell



Each hemoglobin can carry 4 oxygen molecules



More on hemoglobin later…

62

Critical Thinking

•

Tiny size and biconcave shape do what???

63

Critical Thinking

•

Tiny size and biconcave shape do what???

64

White Blood Cells

•

All function in defense against pathogens

•

We will cover extensively in the chapter on

immune systems

65

Platelets

•

Small fragments of cells

•

Formed in bone marrow

•

Function in blood clotting at wound sites

66

Diagram showing the clotting process

The Clotting Process

67

Diagram showing blood

cell production from stem

cells in bone marrow

Blood Cell Production

•

Blood cells are

constantly digested by

the liver and spleen



Components are re-

used

•

Pluripotent stem cells

produce all blood cells

•

Feedback loops that

sense tissue oxygen

levels control red blood

cell production

Fig 42.16, 7

th

 ed

68

Key Concepts:

•

Circulation and gas exchange – why?

•

Circulation – spanning diversity

•

Hearts – the evolution of double circulation

•

Blood circulation and capillary exchange

•

Blood structure and function

•

Gas exchange – spanning diversity

•

Breathing – spanning diversity

•

Respiratory pigments

Hands On

•

Dissect out the circulatory system of your

rat

•

Start by clearing the tissues around the

heart

•

Be especially careful at the anterior end of

the heart – this is where the major blood

vessels emerge

•

Trace the aorta, the vena cava, and as

many additional vessels as possible – use

your manual and lab handout for direction!

69

Hands On

•

Feel and describe the texture of the atria

vs. the ventricles

•

Take cross sections of the heart through

both the atria and the ventricles

•

Examine under the dissecting microscope

•

Do the same with aorta and vena cava

•

Try for a thin enough section to look at

under the compound microscope too

70

71

Gas Exchange

•

Gas Exchange 

≠ Respiration ≠ Breathing



Gas exchange = delivery of O

2

; removal of

CO

2



Respiration = the metabolic process that

occurs in mitochondria and produces ATP



Breathing = ventilation to supply the exchange

surface with O

2

 and allow exhalation of CO

2

72

Diagram showing indirect links between external environment,

respiratory system, circulatory system and tissues.

73

Gas Exchange Occurs at the

Respiratory Surface

•

Respiratory medium = the source of the O

2



 Air for terrestrial animals – air is 21% O

2

 by

volume



Water for aquatic animals – dissolved O

2

varies base on environmental conditions,

especially salinity and temperature; always

lower than in air

74

Gas Exchange Occurs at the

Respiratory Surface

•

Respiratory surface = the site of gas

exchange



Gasses move by diffusion across membranes



Gasses are always dissolved in the interstitial

fluid

•

Surface area is important!

75

Evolution of Gas Exchange Surfaces

•

Skin



Must remain moist – limits environments



Must maintain functional SA / V ratio – limits

3D size

•

Gills



Large SA suspended in water

•

Tracheal systems



Large SA spread diffusely throughout body

•

Lungs



Large SA contained within small space

76

Skin Limits

•

Sponges, jellies and flatworms rely on the

skin as their only respiratory surface

77

Evolution of Gas Exchange Surfaces

•

Skin



Must remain moist – limits environments



Must maintain functional SA / V ratio – limits

3D size

•

Gills



Large SA suspended in water

•

Tracheal systems



Large SA spread diffusely throughout body

•

Lungs



Large SA contained within small space

78

Diagrams and photos of gills

in different animals.

Invertebrate Gills

•

Dissolved oxygen

is limited

•

Behaviors and

structures

increase water

flow past gills to

maximize gas

exchange

Fig 42.20, 7

th

 ed

79

Diagram of countercurrent exchange in fish gills

Countercurrent Exchange in Fish Gills

•

Direction of blood flow allows for maximum

gas exchange – maintains high gradient

Fig 42.21, 7

th

 ed

80

Figure showing countercurrent vs co-current

flow effects on diffusion

How countercurrent flow maximizes diffusion

81

Evolution of Gas Exchange Surfaces

•

Skin



Must remain moist – limits environments



Must maintain functional SA / V ratio – limits

3D size

•

Gills



Large SA suspended in water

•

Tracheal systems



Large SA spread diffusely throughout body

•

Lungs



Large SA contained within small space

82

Diagram and micrograph of insect tracheal system.

Tracheal Systems in Insects

•

Air tubes diffusely penetrate entire body

•

Small openings to the outside limit

evaporation

•

Open circulatory system does not transport

gasses from the exchange surface

•

Body movements ventilate

83

Tracheal Systems in Insects

Rings of chitin

Look familiar???

84

Critical Thinking

•

Name 2 other structures that are held

open by rings

•

Name 2 other structures that are held

open by rings

85

Critical Thinking

86

Evolution of Gas Exchange Surfaces

•

Skin



Must remain moist – limits environments



Must maintain functional SA / V ratio – limits

3D size

•

Gills



Large SA suspended in water

•

Tracheal systems



Large SA spread diffusely throughout body

•

Lungs



Large SA contained within small space

87

Lungs in Spiders, Terrestrial

Snails and Vertebrates

•

Large surface area restricted to small part

of the body

•

Single, small opening limits evaporation

•

Connected to all cells and tissues via a

circulatory system



Dense capillary beds lie directly adjacent to

respiratory epithelium

•

In some animals, the skin supplements

gas exchange (amphibians)

88

Mammalian Lungs

•

Highly branched system of tubes – trachea,

bronchi, and bronchioles

•

Each ends in a cluster of “bubbles” – the

alveoli



Alveoli are surrounded by capillaries



This is the actual site of gas exchange



Huge surface area (100m

2

 in humans)

•

Rings of cartilage keep the trachea open

•

Epiglottis directs food to esophagus

89

Figure and micrograph of lung and alveolus structure.

90

Mammalian Lungs

•

Highly branched system of tubes – trachea,

bronchi, and bronchioles

•

Each ends in a cluster of “bubbles” – the

alveoli



Alveoli are surrounded by capillaries



This is the actual site of gas exchange



Huge surface area (100m

2

 in humans)

•

Rings of cartilage keep the trachea open

•

Epiglottis directs food to esophagus

91

Figure of vascularized alveolus

92

Mammalian Lungs

•

Highly branched system of tubes – trachea,

bronchi, and bronchioles

•

Each ends in a cluster of “bubbles” – the

alveoli



Alveoli are surrounded by capillaries



This is the actual site of gas exchange



Huge surface area (100m

2

 in humans)

•

Rings of cartilage keep the trachea open

•

Epiglottis directs food to esophagus

93

Breathing Ventilates Lungs

•

Positive pressure breathing – amphibians



Air is forced into trachea under pressure



Mouth and nose close, muscle contractions

force air into lungs



Relaxation of muscles and elastic recoil of lungs

force exhalation

94

Breathing Ventilates Lungs

•

Positive pressure breathing – amphibians



Air is forced into trachea under pressure



Mouth and nose close, muscle contractions

force air into lungs



Relaxation of muscles and elastic recoil of lungs

force exhalation

•

Negative pressure breathing – mammals



Air is sucked into trachea under suction

•

Circuit flow breathing – birds



Air flows through entire circuit with every breath

95

Diagram of negative pressure breathing

Negative Pressure Breathing

96

Breathing Ventilates Lungs

•

Positive pressure breathing – amphibians



Air is forced into trachea under pressure



Mouth and nose close, muscle contractions

force air into lungs



Relaxation of muscles and elastic recoil of lungs

forces exhalation

•

Negative pressure breathing – mammals



Air is sucked into trachea under suction

•

Circuit flow breathing – birds



Air flows through entire circuit with every breath

97

Diagram of circuit flow breathing in birds

Flow Through Breathing

•

No residual air left in lungs

•

Every breath brings fresh O

2

 past the exchange

surface

•

Higher lung O

2

 concentration than in mammals

98

Critical Thinking

•

What is the functional advantage of flow-

through breathing for birds???

99

Critical Thinking

•

What is the functional advantage of flow-

through breathing for birds???

100

Respiratory pigments – tying the

two systems together

•

Respiratory pigments are proteins that

reversibly bind O

2

 and CO

2

•

Circulatory systems transport the pigments

to sites of gas exchange

•

O

2

 and CO

2

 molecules bind or are

released depending on gradients of partial

pressure

101

Partial Pressure Gradients Drive

Gas Transport

•

Atmospheric pressure at sea level is

equivalent to the pressure exerted by a

column of mercury 760 mm high = 760 mm

Hg



This represents the total pressure that the

atmosphere exerts on the surface of the earth

•

Partial pressure is the percentage of total

atmospheric pressure that can be assigned

to each component of the atmosphere

102

Atmospheric pressure at

sea level is equivalent to

the pressure exerted by

a column of mercury 760

mm high = 760 mm Hg

(29.92” of mercury)

103

Partial Pressure Gradients Drive

Gas Transport

•

Atmospheric pressure at sea level is

equivalent to the pressure exerted by a

column of mercury 760 mm high = 760 mm

Hg



This represents the total pressure that the

atmosphere exerts on the surface of the earth

•

Partial pressure is the percentage of total

atmospheric pressure that can be assigned

to each component of the atmosphere

104

Partial Pressure Gradients Drive

Gas Transport

•

Each gas contributes to total atmospheric

pressure in proportion to its volume % in

the atmosphere



Each gas contributes a part of total pressure



That part = the partial pressure for that gas

•

The atmosphere is 21% O

2

 and 0.03%

CO

2



Partial pressure of O

2

 is 0.21x760 = 160 mm

Hg



Partial pressure of CO

2

 is 0.0003x760 = 0.23

mm Hg

105

Partial Pressure Gradients Drive

Gas Transport

•

Each gas contributes to total atmospheric

pressure in proportion to its volume % in

the atmosphere



Each gas contributes a part of total pressure



That part = the partial pressure for that gas

•

The atmosphere is 21% O

2

 and 0.03%

CO

2



Partial pressure of O

2

 is 0.21x760 = 160 mm

Hg



Partial pressure of CO

2

 is 0.0003x760 = 0.23

mm Hg

106

Partial Pressure Gradients Drive

Gas Transport

•

Atmospheric gasses dissolve into water in

proportion to their partial pressure and

solubility in water



Dynamic equilibriums can eventually develop

such that the PP in solution is the same as the

PP in the atmosphere



This occurs in the fluid lining the alveoli

107

Critical Thinking

•

If a dynamic equilibrium exists in the

alveoli, will the partial pressures be the

same as in the outside atmosphere???

108

Critical Thinking

•

If a dynamic equilibrium exists in the

alveoli, will the partial pressures be the

same as in the outside atmosphere???

109

Diagram showing

partial pressures of

gasses in various

parts of the body.

This diagram is used

in the next 3 slides.

•

Inhaled air PP’s =

atmospheric PP’s

•

Alveolar PP’s reflect

mixing of inhaled and

exhaled air



Lower PP of O

2

 and

higher PP of CO

2

 than in

atmosphere

110

•

O

2

 and CO

2

 diffuse

based on gradients of

partial pressure



Blood PP’s reflect supply

and usage



Blood leaves the lungs

with high PP of O

2



Body tissues have lower

PP of O

2

 because of

mitochondrial usage



O

2

 moves from blood to

tissues

111

•

Same principles with

CO

2



Blood leaves the lungs

with low PP of CO

2



Body tissues have

higher PP of CO

2

because of

mitochondrial production



CO

2

 moves from tissues

to blood

112

•

When blood reaches

the lungs the gradients

favor diffusion of O

2

into the blood and CO

2

into the alveoli

113

Diagram of hemoglobin structure and how it

changes with oxygen loading.  This diagram

is used in the next 3 slides.

Oxygen Transport

•

Oxygen is not very soluble in water (blood)

•

Oxygen transport and delivery are enhanced

by binding of O

2

 to respiratory pigments

Fig 42.28, 7

th

 ed

114

Oxygen Transport

•

Increase is 2 orders of magnitude!

•

Almost 50 times more O

2 

can be carried this

way, as opposed to simply dissolved in the

blood

115

Oxygen Transport

•

Most vertebrates and some inverts use

hemoglobin for O

2

 transport

•

Iron (in heme group) is the binding element

116

Oxygen Transport

•

Four heme groups per hemoglobin, each

with one iron atom

•

Binding is reversible and cooperative

117

Critical Thinking

•

Binding is reversible and cooperative

•

What does that mean???

118

Critical Thinking

•

Binding is reversible and cooperative

•

What does that mean???

119

Oxygen Transport

•

Reverse occurs during unloading

•

Release of one O

2

 induces shape change

that speeds up the release of the next 3

120

Graph showing how

hemoglobin oxygen saturation

changes with activity.

Oxygen Transport

•

More active

metabolism (ie:

during muscle

use) increases

unloading

•

Note steepness

of curve



O

2

 is unloaded

quickly when

metabolic use

increases

121

Graph showing the

Bohr Shift

Oxygen Transport –

the Bohr Shift

•

More active metabolism

also increases the

release of CO

2



Converts to carbonic

acid, acidifying blood



pH change stimulates

release of additional O

2

Fig 42.29, 7

th

 ed

122

Figure showing

how carbon

dioxide is

transported from

tissues to lungs.

This figure is used

in the next 3

slides.

Carbon Dioxide

Transport

•

Red blood cells also assist in

CO

2

 transport



7% of CO

2

 is transported

dissolved in plasma



23% is bound to amino groups of

hemoglobin in the RBC’s



70% is converted to bicarbonate

ions inside the RBC’s

123

Carbon Dioxide

Transport

•

CO

2

 in RBC’s

reacts with water

to form carbonic

acid (H

2

CO

3

)

•

H

2

CO

3

 dissociates

to bicarbonate

(HCO

3

-

) and H

+

124

Carbon Dioxide

Transport

•

Most H

+

 binds to

hemoglobin



This limits blood

acidification

•

HCO

3

-

 diffuses

back into plasma

for transport

125

Carbon Dioxide

Transport

•

Reverse occurs

when blood

reaches the lungs



Conversion back to

CO

2

 is driven by

diffusion gradients

as CO

2

 moves into

the lungs

126

REVIEW 

– Key Concepts:

•

Circulation and gas exchange – why?

•

Circulation – spanning diversity

•

Hearts – the evolution of double circulation

•

Blood circulation and capillary exchange

•

Blood structure and function

•

Gas exchange – spanning diversity

•

Breathing – spanning diversity

•

Respiratory pigments

Hands On

•

Dissect out the respiratory system of your

rat

•

Trace the trachea into the lungs

•

Examine trachea and lungs under the

dissecting microscope

•

Try for thin enough sections to also

examine with the compound microscope

127