Transcript 42gas exchange

Chap 42
Circulation and Gas Exchange
Gastrovascular
cavities and
body walls only
two layers thick
allow for easy
distribution of
nutrients and
gas exchange
• In insects, other arthropods, and most mollusks,
blood bathes organs directly in an open
circulatory system.
• There is no distinction
between blood and
interstitial fluid, collectively
called hemolymph.
• One or more hearts pump
the hemolymph into
interconnected sinuses
surrounding the organs,
allowing exchange
between hemolymph
and body cells.
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Fig. 42.2a
Blood empties
into sinus
Blood always stays in a blood vessel more efficient
• Arteries carry blood to capillaries
– The sites of chemical exchange between the
blood and interstitial fluid
• Veins
– Return blood from capillaries to the heart
Blood going
through body
under low
pressure
The pulmonary
and systemic
circuits are not
completely
separated
Completely separation
ensures oxygenated
blood going to systemic
circuit under high
pressure
• Vertebrate circulatory systems
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
Lung and skin capillaries
Lung capillaries
Lung capillaries
FISHES
Gill capillaries
Artery
Pulmocutaneous
circuit
Gill
circulation
Heart:
ventricle (V)
A
Atrium (A)
Systemic
Vein circulation
Systemic capillaries
Right
systemic
aorta
Pulmonary
circuit
A
A
V
Right
V
Left
Right
Systemic
circuit
Systemic capillaries
Figure 42.4
Pulmonary
circuit
Left
Systemic
V aorta
Left
A
Systemic capillaries
A
V
Right
A
V
Left
Systemic
circuit
Systemic capillaries
• A powerful four-chambered heart
– Was an essential adaptation of the endothermic
way of life characteristic of mammals and birds
Mammalian Circulation: The
Pathway
• Heart valves
– Dictate a one-way flow of blood through the
heart
Circulation movie
1. Pearson circulatory Lab
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2. Heart Review
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gy%20Lab%20Simulations/cardio1/intro.html
• A cardiac cycle is one complete sequence of
pumping, as the heart contracts, and filling, as it
relaxes and its chambers fill with blood.
– The contraction phase is called systole, and the
relaxation phase is called diastole.
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ECG Video
• All blood vessels
– Are built of similar tissues
– Have three similar layers
Artery
Vein
Basement
membrane
Endothelium
100 µm
Valve
Endothelium
Smooth
muscle
Connective
tissue
Endothelium
Capillary
Smooth
muscle
Connective
tissue
Artery
Vein
Venule
Figure 42.9
Arteriole
Single wall capillaries ideal for
allowing diffusion through and
between endothelial cells
Thicker and
more elastic
• The apparent
contradiction
between
observations and
the law of
continuity can be
resolved when we
recognize that the
total crosssectional area of
capillaries
determines flow
rate in each. Fig. 42.10
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Speed of blood
decreases in the
capillaries
because ?
What are two
reasons why the
pressure
decreases?
• Fluids exert a force called hydrostatic pressure
against surfaces they contact, and it is that
pressure that drives fluids through pipes.
– Fluids always flow from areas of high pressure to
areas of lower pressure.
– Blood pressure, the hydrostatic force that blood
exerts against vessel walls, is much greater in
arteries than in veins and is highest in arteries when
the heart contracts during ventricular systole,
creating the systolic pressure.
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• When you take your pulse by placing your
fingers on your wrist, you can feel an artery
bulge with each heartbeat.
– The surge of pressure is partly due to the narrow
openings of arterioles impeding the exit of blood
from the arteries, the peripheral resistance.
– Thus, when the heart contracts, blood enters the
arteries faster than it can leave, and the vessels
stretch from the pressure.
– The elastic walls of the arteries snap back during
diastole, but the heart contracts again before enough
blood has flowed into the arterioles to completely
relieve pressure in the arteries, the diastolic
pressure.
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• A sphygmomanometer, an inflatable cuff
attached to a pressure gauge, measures blood
pressure fluctuations in the brachial artery of the
arm over the cardiac cycle.
– The arterial blood pressure of a healthy human
oscillates between about 120 mm Hg at systole and
70 mm Hg at diastole.
Fig. 42.11
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Smooth muscles and
hormones can regulate the
amount of blood in
capillaries
only 5-10% have blood in
them at any one time
The osmotic pressure due to
the proteins in the blood
plasma allow for about 85%
of the fluids to reenter the
capillaries - the remaining
15% that remain in the
interstitual fluid returns via
the lymph system
• The difference between blood pressure and
osmotic pressure
– Drives fluids out of capillaries at the arteriole
end and into capillaries at the venule end
Tissue cell
Capillary
Red
blood
cell
Net fluid
movement out
Net fluid
movement in
15 m
At the arterial end of a
capillary, blood pressure is
greater than osmotic pressure,
and fluid flows out of the
capillary into the interstitial fluid.
At the venule end of a capillary, blood
pressure is less than osmotic pressure,
and fluid flows from the interstitial fluid
into the capillary.
Direction of
blood flow
Blood pressure
Osmotic pressure
Pressure
Capillary
INTERSTITIAL FLUID
Inward flow
Outward flow
Arterial end of capillary
Figure 42.14
Venule end
If the hydrostatic pressure
increases there is an
increases OUTFLOW of
fluids into the cells
If hydrostatic pressure
decreases there will be an Net
INFLOW of material from the
cells
Decreasing the
plasma proteins
lowers the
osmotic
pressure of the
blood causing
more fluid to be
pushed outward
8. The lymphatic system returns fluid
to the blood and aids in body defense
• Fluids and some blood proteins that leak from the
capillaries into the interstitial fluid are returned to
the blood via the lymphatic system.
– Fluid enters this system by diffusing into tiny lymph
capillaries intermingled among capillaries of the
cardiovascular system.
– Once inside the lymphatic system, the fluid is called
lymph, with a composition similar to the interstitial
fluid.
– The lymphatic system drains into the circulatory
system near the junction of the venae cavae with the
right atrium.
• Lymph vessels, like veins, have valves that
prevent the backflow of fluid toward the
capillaries.
– Rhythmic contraction of the vessel walls help draw
fluid into lymphatic capillaries.
– Also like veins, lymph vessels depend mainly on
the movement of skeletal muscle to squeeze fluid
toward the heart.
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• Along a lymph vessels are organs called lymph
nodes.
– The lymph nodes filter the lymph and attack
viruses and bacteria.
– Inside a lymph node is a honeycomb of
connective tissue with spaces filled with white
blood cells specialized for defense.
• When the body is fighting an infection, these cells
multiply, and the lymph nodes become swollen.
• In addition to defending against infection and
maintaining the volume and protein
concentration of the blood, the lymphatic system
transports fats from the digestive tract to the
circulatory system.
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Filarial worms
can block
lymph, causing
a build of up of
fluid Elephantiasis
Blood Composition and Function
• Blood consists of several kinds of cells
– Suspended in a liquid matrix called plasma
• The cellular elements
– Occupy about 45% of the volume of blood
Plasma
• Blood plasma is about 90% water
• Among its many solutes are
– Inorganic salts in the form of dissolved ions,
sometimes referred to as electrolytes
Found in bone
marrow - ribs,
vertebrae,
breastbone,
pelvis
Low O2 triggers
erythropoeitin
At high altitudes
more red blood
cells are
produced
Preadapted for
high altitudes
Ex:
thromboplastin
Cascade effect: each
step as as an enzyme
catalyzing many more
reactions at each step
each level results in
many more molecules
A blood clot or thrombus can
result in a thromboembolus
in the brain it could result in a
stroke
in the heart it could result in a
myocardial infarction or heart
attack
Fatty deposits result in Atherosclerosis -more
likely to catch thrombus
LDL may increase plaque deposits - HDL may
decrease
• Hypertension (high blood pressure) promotes
atherosclerosis and increases the risk of heart
disease and stroke.
– According to one hypothesis, high blood pressure
causes chronic damage to the endothelium that lines
arteries, promoting plaque formation.
– Hypertension is simple to diagnose and can usually
be controlled by diet, exercise, medication, or a
combination of these.
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• To some extent, the tendency to develop
hypertension and atherosclerosis is inherited.
• Nongenetic factors include smoking, lack of
exercise, a diet rich in animal fat, and abnormally
high levels of cholesterol in the blood.
• One measure of an individual’s cardiovascular
health or risk of arterial plaques can be gauged by
the ratio of low-density lipoproteins (LDLs) to
high-density lipoproteins (HDLs) in the blood.
– LDL is associated with depositing of cholesterol
in arterial plaques.
– HDL may reduce cholesterol deposition.
4 Basic Needs of Gas
Exchange
1. A thin, moist respiratory
surface of adequate
dimension
2. A method of transport of
gases to the inner cells
Gas exchange is
needed for cell
respiration
3. A means of protecting the
fragile respiratory surface
4. A way to keep the surface
moist while limiting water
loss
• The part of an animal where gases are exchanged with
the environment is the respiratory surface.
– Movements of CO2 and O2 across the respiratory
surface occurs entirely by diffusion.
– The rate of diffusion is proportional to the surface
area across which diffusion occurs, and inversely
proportional to the square of the distance through
which molecules must move.
– Therefore, respiratory surfaces tend to be thin and
have large areas, maximizing the rate of gas
exchange.
– In addition, the respiratory surface of terrestrial and
aquatic animals are moist to maintain the cell
membranes and thus gases must first dissolve in
water.
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Large SA/Vol ratio
Body surface
used in gas
exchange
Evaginatation
increases
surface area
gills
Lungs-invaginations +
circulatory system
Invaginations
such as trachea
2. Gills are respiratory adaptation
of most aquatic animals
• Gills are outfoldings of the body surface that are
suspended in water.
– The total surface area of gills is often much greater
than that of the rest of the body.
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Polychaete worm
• The feathery gills projecting from a salmon
– Are an example of a specialized exchange
system found in animals
Figure 42.1
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Water is moving
countercurrent
to blood flow
Blood Flow
• This flow pattern is countercurrent exchange.
– As blood moves anteriorly in a gill capillary, it
becomes more and more loaded with oxygen, but it
simultaneously encounters water with even higher
oxygen concentrations because it is just beginning
its passage over the gills.
– All along the gill
capillary, there is a
diffusion gradient
favoring the transfer
of oxygen from
water to blood.
Fig. 42.20
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Tracheal systems and lungs are respiratory
adaptations of terrestrial animals
• As a respiratory medium, air has many
advantages over water.
– Air has a much higher concentration of oxygen.
– Also, since O2 and CO2 diffuse much faster in air than
in water, respiratory surfaces exposed to air do not
have to be ventilated as thoroughly as gills.
– When a terrestrial animal does ventilate, less energy is
needed because air is far lighter and much easier to
pump than water and much less volume needs to be
breathed to obtain an equal amount of O2.
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Tracheal systems in
insects allow for gas to
be transported directly
to most cells -no need
for hemoglobin to
transport oxygen
Spiracles control the
opening the trachea
Fig. 42.22
• The tracheal tubes
– Supply O2 directly to body cells
Body
cell
Air
sac
Tracheole
Trachea
Air
Tracheoles
Mitochondria
Body wall
Myofibrils
(b) This micrograph shows cross
sections of tracheoles in a tiny
piece of insect flight muscle (TEM).
Each of the numerous mitochondria
in the muscle cells lies within about
5 µm of a tracheole.
Figure 42.22b
2.5 µm
• Unlike branching tracheal systems, lungs are
restricted to one location.
– Because the respiratory surface of the lung is not in
direct contact with all other parts of the body, the
circulatory system transports gases between the
lungs and the rest of the body.
– Lungs have a dense net of capillaries just under the
epithelium that forms the respiratory surface.
– Lungs have evolved in spiders, terrestrial snails, and
vertebrates.
Book lung found in spiders
subdivisions increase surface area
Increasing the subdivision of the lungs increases the surface area for gas exchange
Mammalian Respiratory Systems:
A Closer Look
• A system of branching ducts
» Conveys air to theBranch
lungs
Branch
from the
pulmonary
artery
(oxygen-poor
blood)
from the
pulmonary
vein
(oxygen-rich
blood)
Terminal
bronchiole
Nasal
cavity
Pharynx
Left
lung
Alveoli
50 µm
50 µm
Larynx
Esophagus
Trachea
Right lung
Bronchus
Bronchiole
Diaphragm
Heart
SEM
Figure 42.23
Colorized SEM
How an Amphibian Breathes
• An amphibian such as a frog
– Ventilates its lungs by positive pressure
breathing, which forces air down the trachea
How a Mammal Breathes
• Mammals ventilate their lungs
– By negative pressure breathing, which pulls air
into the lungs
Rib cage
expands as
rib muscles
contract
Air inhaled
Rib cage gets
smaller as
rib muscles
relax
Air exhaled
Lung
Diaphragm
INHALATION
Diaphragm contracts
(moves down)
Figure 42.24
EXHALATION
Diaphragm relaxes
(moves up)
Higher air pressure
forces air in
Lower pressure
Negative pressure breathing
Tidal volume is a normal breath
The volume increases by the
diaphragm moving down and the
rib cage moving up and out
Vital capacity is the max volume of a breath
Residual volume is left over after exhalation
- old air that will be mixed in with the new
• The volume of air an animal inhales and
exhales with each breath is called tidal volume.
– It averages about 500 mL in resting humans.
• The maximum tidal volume during forced
breathing is the vital capacity, which is about
3.4 L and 4.8 L for college-age females and
males, respectively.
– The lungs hold more air than the vital capacity, but
some air remains in the lungs, the residual volume,
because the alveoli do not completely collapse.
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How a Bird Breathes
• Besides lungs, bird have eight or nine air sacs
– That function as bellows that keep air flowing through
the lungs
Air
Air
Anterior
air sacs
Trachea
Posterior
air sacs
Lungs
Lungs
Air tubes
(parabronchi)
in lung
INHALATION
Air sacs fill
EXHALATION
Air sacs empty; lungs fill
Figure 42.25
Parabronchi
allow for one
way flow of air
through
lungs
1 mm
• This system completely exchanges the air in the
lungs with every breath.
– Therefore, the maximum lung oxygen
concentrations are higher in birds than in mammals.
– Partly because of this efficiency advantage, birds
perform much better than mammals at high altitude.
• For example, while human mountaineers experience
tremendous difficulty obtaining oxygen when climbing
the Earth’s highest peaks, several species of birds easily
fly over the same mountains during migration.
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High CO2 levels increase
the acidity of blood and
cerebrospinal fluid
triggering the medulla to
increase the depth and
rate of breathing
Low O2 levels trigger
sensors in the Carotid
arteries and the Aorta
to trigger the medulla
• Our breathing control centers are located in
two brain regions, the medulla oblongata and
the pons.
– Aided by the control center in the pons, the
medulla’s center sets basic breathing rhythm,
triggering contraction of the diaphragm and rib
muscles.
– A negative-feedback mechanism via stretch
receptors prevents our lungs from overexpanding by
inhibiting the breathing center in the medulla.
• Concept 42.7: Respiratory pigments bind
and transport gases
• The metabolic demands of many organisms
– Require that the blood transport large quantities
of O2 and CO2
The Role of Partial Pressure
Gradients
• Gases diffuse down pressure gradients
– In the lungs and other organs
• Diffusion of a gas
– Depends on differences in a quantity called
partial pressure
Partial pressure
of O2 is 760 mm
Hg X 21%= 160
Oxygen Transport
• The respiratory pigment of almost all
vertebrates
– Is the protein hemoglobin, contained in the
erythrocytes
• Like all respiratory pigments
– Hemoglobin must reversibly bind O2, loading
O2 in the lungs and unloading it in other parts
of the body
One molecule of hemoglobin
has 4 prosthetic heme groups,
allowing it to bind to 4 O2
molecules
Cooperativity
Heme group
-the binding of one O2 allows the
next O2 to bind easier
Iron atom
O2 loaded
in lungs
O2 unloaded
In tissues
Figure 42.28
Polypeptide chain
O2
O2
• Loading and unloading of O2
– Depend on cooperation between the subunits of
the hemoglobin molecule
• The binding of O2 to one subunit induces
the other subunits to bind O2 with more
affinity
• Cooperative O2 binding and release
– Is evident in the dissociation curve for
hemoglobin
• A drop in pH
– Lowers the affinity of hemoglobin for O2
H+ from carbonic acid can act as a negative
modulator for hemoglobin, causing it to release
more O2
Bohr shifts curve to the right
At 40 mm HG
pH 7.2= 60 mm Hg
pH 7.4= 70 mm Hg
• As with all proteins, hemoglobin’s
conformation is sensitive to a variety of factors.
• For example, a drop in pH
lowers the affinity of hemoglobin for O2, an effect
called the Bohr shift.
• Because CO2 reacts with
water to form carbonic acid,
an active tissue will lower
the pH of its surroundings
and induce hemoglobin
to release more oxygen.
Fig. 42.28b
Higher temps
right shift curve
making it easier
to dump Oxygen
Animals with a
high metabolic
rate have a right
shifted curve
Hb acts as a
buffer in picking
up H+
Most CO2 travels
in the plasma as
a bicarbonate
ion
Bet You Didn't Know They Treat Meat With
Carbon Monoxide To Fool You. Hemoglobin
has a great affinity to CO – it binds and turns
red, giving even old meat the appearance of
freshness.
If you breath in CO,
hemoglobin will not
release it and not be able
to transport O2.
Deep-diving air-breathers stockpile
oxygen and deplete it slowly
• When an air-breathing animal swims underwater,
it lacks access to the normal respiratory medium.
– Most humans can only hold their breath for 2 to 3 minutes and swim to depths of 20 m or so.
In comparison with diving mammals, humans are poorly adapted to life in the water. In 2002,
free-diving champion Mandy-Rae Cruikshank set a women’s world record for static apnea of 6
minutes 13 seconds (the men’s record, set in 2001 by Scott Campbell, is 6 minutes 45 seconds)
– However, a variety of seals,
sea turtles, and whales can
stay submerged for much
longer times and reach
much greater depths.
Weddell Seal Dive Adaptations
• Stores more O2 in its blood
• Has more blood, has larger
spleen for storage of blood
• Has higher amount of O2
storing protein called
myoglobin in muscles
• Heart rate(125>10) and O2
consumption rate decrease
• Blood to muscles restricted
• Blood routed to vital organs brain, eyes /peripheral
vasoconstriction.
A school of salema attempts to outmaneuver a hungry sea lion near the Galápagos Islands by
circling to confuse the predator. Galápagos sea lions dive down some 120 feet (37 meters) on
average to feed, returning to the surface after a minute or two to breathe.
Pearson Daphnia Temp Lab
Turn in Lab Quiz 2 tomorrow