Transcript Lecture #11 – Animal Circulation and Gas Exchange Systems

Lecture #10 – Animal Circulation
and Gas Exchange Systems
1
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
2
Animals use O2 and produce CO2
• All animals are aerobic
Lots of oxygen is required to support active
mobility
Some animals use lots of oxygen to maintain
body temperature
• All animals produce CO2 as a byproduct of
aerobic respiration
• Gasses must be exchanged
Oxygen must be acquired from the environment
Carbon dioxide must be released to the
3
environment
Animals use O2 and produce CO2
• 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
4
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
5
Critical Thinking
• Why isn’t diffusion adequate for exchange
in a 3D large animal???
6
Critical Thinking
• Why isn’t diffusion adequate for exchange
in a 3D large animal???
• Surface area / volume ratio becomes too
small
• Remember, area is a square function;
volume is a cubic function
7
Critical Thinking
• But…..plants rely on
diffusion for gas
exchange…..how do
they get so big???
8
Critical Thinking
• But…..plants rely on
diffusion for gas
exchange…..how do
they get so big???
• Their living tissue is
close to the surface
and exposed to air –
either in the open
atmosphere or in the
soil atmosphere
9
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
10
Virtually every cell in a sponge is in direct
contact with the water – little circulation is
required
Diagram of sponge structure
11
• 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)
Diagram of jellyfish structure, and photos
12
Circulation systems have evolved
over time
• Most invertebrates (esp. insects) have an
open circulatory system
 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
Diagram of open
circulatory system in a
grasshopper
13
Circulation systems have evolved
over time
• Closed circulatory systems separate blood
from interstitial fluid
 Metabolic energy is
used to pump blood
through blood vessels
 Blood is contained
within the vessels
 Exchange occurs by
diffusion in capillary
beds
Diagram of a closed
circulatory system, plus
a diagram showing an
earthworm circulatory
system
14
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
15
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
We’ll go over these
Infiltrate all tissues in the body
16
step by step
Chambered heart pumps blood
• Atria receive blood
• Ventricles pump
blood
Diagram of a chambered heart
• One-way valves
direct blood flow
17
Critical Thinking
• Atria receive blood; ventricles pump
• Given that function, what structure would
you predict???
18
Critical Thinking
• Atria receive blood; ventricles pump
• Given that function, what structure would
you predict???
• Atria are soft, flexible chambers
• Ventricles have much more muscular walls
19
Chambered heart pumps blood
• Atria receive blood
Soft walled, flexible
• Ventricles pump
blood
Thick, muscular
walls
Diagram of a chambered heart
• One-way valves
direct blood flow
20
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
Diagram showing
artery, vein and
capillary bed
21
Note that blood vessel names reflect the
direction of flow, NOT the amount of
oxygen in the blood
• Arteries carry blood
AWAY from the heart
Arterial blood is always
under pressure
It is NOT always
oxygenated
Diagram of blood
circulation pattern
in humans
• Veins carry blood TO
the heart
22
Capillary beds facilitate exchange
•
•
•
•
Capillary beds separate arteries from veins
Highly branched and very tiny
Infiltrate all tissues in the body
More later
Diagram showing
artery, vein and
capillary bed
23
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
24
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
25
Evolution of double circulation –
not all animals have a 4-chambered heart
Diagram showing progression from a 1chambered heart to a 4-chambered heart.
This diagram is used in the next 12 slides.
26
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
27
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
28
Amphibians have a 3-chambered heart
• Two atria, one ventricle
• Ventricle pumps to 2 circuits
One circuit goes to lungs and skin
to release CO2 and acquire O2
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 O2 delivery to the body
29
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
30
Critical Thinking
• What is a disadvantage of a 3 chambered
heart???
31
Critical Thinking
• What is a disadvantage of a 3 chambered
heart???
• Oxygen rich and oxygen poor blood mix in
the ventricle
• Less than maximum efficiency
32
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
33
Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• What does this mean???
34
Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT monophyletic
• Mammals and birds evolved from separate
reptilian ancestors
Phylogenetic tree showing
the diversification of
vertebrates
35
Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• Four-chambered hearts evolved
independently
• What’s this called???
36
Mammals and birds have
4-chambered hearts
• Mammals and birds are NOT
monophyletic
• Four-chambered hearts evolved
independently
• Convergent evolution
37
Review: evolution of double circulation
38
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
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???
• Arteries are under more pressure than
veins
• Capillaries are the exchange surface
42
Form reflects function…
• Arteries are
under more
pressure than
veins
• Capillaries are
the exchange
surface
Diagram showing
artery, vein and
capillary bed
43
Blood
pressure
and velocity
drop as
blood moves
through
capillaries
Graph showing relationships
between blood pressure,
blood velocity, and the crosssectional area of different
kinds of blood vessels –
arteries to capillaries to
veins. This same graph is
on the next 3 slides.
44
Total crosssectional area
in capillary
beds is much
higher than in
arteries or
veins; slows
flow
45
Velocity
increases as
blood passes
into veins
(smaller crosssectional
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???
• Velocity is controlled by gravity in rivers
• The Coastal Plain is just a few meters
above sea level – little gravity to force
forward momentum
• The water slows; the rivers meander
• The functional equivalent to blood
meandering through a capillary bed
49
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…
50
Bed fully open
Bed closed, throughflow only
Diagram showing
sphincter muscle
control over
capillary flow.
Micrograph of a
capillary bed.
Note scale – capillaries
are very tiny!!
51
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
52
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
53
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 crosssectional area
54
Bulk Flow in Capillary Beds
Remember: Ψ = P – s
Diagram showing osmotic changes across a capillary bed
55
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
56
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
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
Blood Components
Chart listing all blood components – both liquid and cellular
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 O2 and some CO2
White blood cells defend against pathogens
Platelets promote clotting
61
Red Blood Cells
•
•
•
•
•
Most numerous of all blood cells
5-6 million per mm3 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???
• Increase surface area
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
The Clotting Process
Diagram showing the clotting process
67
Blood Cell Production
• Blood cells are
constantly digested by
the liver and spleen
 Components are reused
• Pluripotent stem cells
produce all blood cells
• Feedback loops that
sense tissue oxygen
levels control red blood
cell production
Fig 42.16, 7th ed
Diagram showing blood
cell production from stem
cells in bone marrow
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
69
Gas Exchange
• Gas Exchange ≠ Respiration ≠ Breathing
Gas exchange = delivery of O2; removal of
CO2
Respiration = the metabolic process that
occurs in mitochondria and produces ATP
Breathing = ventilation to supply the exchange
surface with O2 and allow exhalation of CO2
70
Diagram showing indirect links between external environment,
respiratory system, circulatory system and tissues.
71
Gas Exchange Occurs at the
Respiratory Surface
• Respiratory medium = the source of the O2
 Air for terrestrial animals – air is 21% O2 by
volume
Water for aquatic animals – dissolved O2
varies base on environmental conditions,
especially salinity and temperature; always
lower than in air
72
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!
73
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
74
Skin Limits
• Sponges, jellies and flatworms rely on the
skin as their only respiratory surface
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
Invertebrate Gills
• Dissolved oxygen
is limited
• Behaviors and
structures
increase water
flow past gills to
maximize gas
exchange
Diagrams and photos of gills
in different animals.
77
Fig 42.20, 7th ed
Countercurrent Exchange in Fish Gills
• Direction of blood flow allows for maximum
gas exchange – maintains high gradient
Diagram of countercurrent exchange in fish gills
78
Fig 42.21, 7th ed
How countercurrent flow maximizes diffusion
Figure showing countercurrent vs co-current
flow effects on diffusion
79
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
80
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
Diagram and micrograph of insect tracheal system.
81
Tracheal Systems in Insects
Rings of chitin
Look familiar???
82
Critical Thinking
• Name 2 other structures that are held
open by rings
83
Critical Thinking
• Name 2 other structures that are held
open by rings
• Xylem cells by rings of lignin
• Vertebrate trachea by rings of cartilage
Diagrams and micrographs of tracheae, xylem and trachea
84
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
85
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)
86
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 (100m2 in humans)
• Rings of cartilage keep the trachea open
• Epiglottis directs food to esophagus
87
Figure and micrograph of lung and alveolus structure.
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 (100m2 in humans)
• Rings of cartilage keep the trachea open
• Epiglottis directs food to esophagus
89
Figure of vascularized alveolus
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 (100m2 in humans)
• Rings of cartilage keep the trachea open
• Epiglottis directs food to esophagus
91
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
92
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
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
• Negative pressure breathing – mammals
Air is sucked into trachea under suction
• Circuit flow breathing – birds
Air flows through entire circuit with every breath
94
Negative Pressure Breathing
Diagram of negative pressure breathing
95
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
96
Flow Through Breathing
• No residual air left in lungs
• Every breath brings fresh O2 past the exchange
surface
• Higher lung O2 concentration than in mammals
Diagram of circuit flow breathing in birds
97
Critical Thinking
• What is the functional advantage of flowthrough breathing for birds???
98
Critical Thinking
• What is the functional advantage of flowthrough breathing for birds???
• More oxygen = more ATP = more energy
• Flight requires a LOT of energy
99
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
100
Respiratory pigments – tying the
two systems together
• Respiratory pigments are proteins that
reversibly bind O2 and CO2
• Circulatory systems transport the pigments
to sites of gas exchange
• O2 and CO2 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% O2 and 0.03%
CO2
Partial pressure of O2 is 0.21x760 = 160 mm
Hg
Partial pressure of CO2 is 0.0003x760 = 0.23105
mm Hg
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% O2 and 0.03%
CO2
Partial pressure of O2 is 0.21x760 = 160 mm
Hg
Partial pressure of CO2 is 0.0003x760 = 0.23106
mm Hg
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???
• NO!!!
Breathing does not completely replace
alveolar air with fresh air
The PP of O2 is lower and the PP of CO2 is
higher in the alveoli than in the atmosphere
109
• Inhaled air PP’s =
atmospheric PP’s
• Alveolar PP’s reflect
mixing of inhaled and
exhaled air
Diagram showing
partial pressures of
gasses in various
parts of the body.
This diagram is used
in the next 3 slides.
Lower PP of O2 and
higher PP of CO2 than in
atmosphere
110
• O2 and CO2 diffuse
based on gradients of
partial pressure
Blood PP’s reflect supply
and usage
Blood leaves the lungs
with high PP of O2
Body tissues have lower
PP of O2 because of
mitochondrial usage
O2 moves from blood to
tissues
111
• Same principles with
CO2
Blood leaves the lungs
with low PP of CO2
Body tissues have
higher PP of CO2
because of
mitochondrial production
CO2 moves from tissues
to blood
112
• When blood reaches
the lungs the gradients
favor diffusion of O2
into the blood and CO2
into the alveoli
113
Oxygen Transport
• Oxygen is not very soluble in water (blood)
• Oxygen transport and delivery are enhanced
by binding of O2 to respiratory pigments
Diagram of hemoglobin structure and how it
changes with oxygen loading. This diagram
is used in the next 3 slides.
114
Fig 42.28, 7th ed
Oxygen Transport
• Increase is 2 orders of magnitude!
• Almost 50 times more O2 can be carried this
way, as opposed to simply dissolved in the
blood
115
Oxygen Transport
• Most vertebrates and some inverts use
hemoglobin for O2 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???
• Binding one O2 induces shape change that
speeds up the binding of the next 3
• Remember, hemoglobin is a protein!
Binding events are both chemical and
physical
119
Oxygen Transport
• Reverse occurs during unloading
• Release of one O2 induces shape change
that speeds up the release of the next 3
120
Oxygen Transport
• More active
metabolism (ie:
during muscle
use) increases
unloading
• Note steepness
of curve
O2 is unloaded
quickly when
metabolic use
increases
Graph showing how
hemoglobin oxygen saturation
changes with activity.
121
Oxygen Transport –
the Bohr Shift
• More active metabolism
also increases the
release of CO2
Graph showing the
Bohr Shift
Converts to carbonic
acid, acidifying blood
pH change stimulates
release of additional O2
122
Fig 42.29, 7th ed
Carbon Dioxide
Transport
• Red blood cells also assist in
CO2 transport
Figure showing
how carbon
dioxide is
transported from
tissues to lungs.
This figure is used
in the next 3
slides.
7% of CO2 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
• CO2 in RBC’s
reacts with water
to form carbonic
acid (H2CO3)
• H2CO3 dissociates
to bicarbonate
(HCO3-) and H+
124
Carbon Dioxide
Transport
• Most H+ binds to
hemoglobin
This limits blood
acidification
• HCO3- diffuses
back into plasma
for transport
125
Carbon Dioxide
Transport
• Reverse occurs
when blood
reaches the lungs
Conversion back to
CO2 is driven by
diffusion gradients
as CO2 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
127