chap 42 circulation and gas exchange. gastrovascular cavities and body walls only two layers thick...
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Chap 42
Circulation and Gas Exchange
Gastrovascular cavities and body walls only two layers thick allow for easy distribution of nutrients 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 empties into sinus
Blood always stays in a blood vessel - more efficient
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
Blood going through body under low pressure
The pulmonary and systemic circuits are not completely separated
The pulmonary and systemic circuits are not completely separated
Completely separation ensures oxygenated blood going to systemic circuit under high pressure
Completely separation ensures oxygenated blood going to systemic circuit under high pressure
FISHES AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS
Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries
Lung capillaries Lung capillariesLung and skin capillariesGill capillaries
Right Left Right Left Right Left Systemic
circuitSystemic
circuit
Pulmocutaneouscircuit
Pulmonarycircuit
Pulmonarycircuit
SystemiccirculationVein
Atrium (A)
Heart:ventricle (V)
Artery Gillcirculation
A
V VV VV
A A A AALeft Systemicaorta
Right systemicaorta
Figure 42.4
• Vertebrate circulatory systems
• 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
1. Pearson circulatory LabTurn in Lab Quiz tommorrow
2. Heart Review
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http://www.midpac.edu/~biology/Intro%20Biology/PH%20Biology%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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• All blood vessels– Are built of similar tissues– Have three similar layers
Figure 42.9
Artery Vein
100 µm
Artery Vein
ArterioleVenule
Connectivetissue
Smoothmuscle
Endothelium
Connectivetissue
Smoothmuscle
EndotheliumValve
Endothelium
Basementmembrane
Capillary
Thicker and more elastic
Thicker and more elastic
Single wall capillaries ideal for allowing diffusion through and between endothelial cells
Single wall capillaries ideal for allowing diffusion through and between endothelial cells
• The apparent contradiction between observations and the law of continuity can be resolved when we recognize that the total cross-sectional area of capillaries determines flow rate in each.
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Fig. 42.10
Speed of blood decreases in the capillaries because ?
Speed of blood decreases in the capillaries because ?
What are two reasons why the pressure decreases?
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.
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Fig. 42.11
Smooth muscles and hormones can regulate the amount of blood in capillaries
only 5-10% have blood in them at any one time
Smooth muscles and hormones can regulate the amount of blood in capillaries
only 5-10% have blood in them at any one time
blood circulation.mov
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 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
At the arterial end of acapillary, blood pressure is
greater than osmotic pressure,and fluid flows out of the
capillary into the interstitial fluid.
CapillaryRedbloodcell
15 m
Tissue cell INTERSTITIAL FLUID
Capillary
Net fluidmovement out
Net fluidmovement in
Direction of blood flow
Blood pressure
Osmotic pressure
Inward flow
Outward flow
Pre
ssur
e
Arterial end of capillary Venule end
At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary.
Figure 42.14
If the hydrostatic pressure increases there is an increases OUTFLOW of fluids into the cells
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
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
Decreasing the plasma proteins lowers the osmotic pressure of the blood causing more fluid to be pushed outward
• 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.
8. The lymphatic system returns fluid to the blood and aids in body defense
• 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
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
Found in bone marrow - ribs, vertebrae, breastbone, pelvis
Low O2 triggers erythropoeitin
Low O2 triggers erythropoeitin
Preadapted for high altitudes
Preadapted for high altitudes
At high altitudes more red blood cells are produced
At high altitudes more red blood cells are produced
Ex: thromboplastin
Ex: thromboplastin
Cascade effect: each step as as an enzyme catalyzing many more reactions at each step -
each level results in many more molecules
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
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
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.
Gas exchange is needed for cell respiration
Gas exchange is needed for cell respiration
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
3. A means of protecting the fragile respiratory surface
4. A way to keep the surface moist while limiting water loss
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
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 ratioLarge SA/Vol ratioBody surface used in gas exchange
Body surface used in gas exchange
Evaginatation increases surface area
Evaginatation increases surface area
gillsgills
Invaginations such as trachea
Invaginations such as trachea
Lungs-invaginations + circulatory system
Lungs-invaginations + circulatory system
• 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.
2. Gills are respiratory adaptation of most aquatic animals
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Polychaete worm
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• The feathery gills projecting from a salmon
– Are an example of a specialized exchange system found in animals
Figure 42.1
Water is moving countercurrent to blood flow
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.
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Fig. 42.20
• 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.
Tracheal systems and lungs are respiratory adaptations of terrestrial animals
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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
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
Airsac
Body cell
Trachea
Tracheole
TracheolesMitochondria
Myofibrils
Body wall
(b) This micrograph shows crosssections of tracheoles in a tinypiece of insect flight muscle (TEM).Each of the numerous mitochondriain the muscle cells lies within about5 µm of a tracheole.
Figure 42.22b 2.5 µm
Air
• 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
Book lung found in spiders
subdivisions increase surface area
Increasing the subdivision of the lungs increases the surface area for gas exchangeIncreasing 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 the lungs
Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole
Branch from thepulmonaryartery(oxygen-poor blood)
Alveoli
Colorized SEMSEM
50 µ
m
50 µ
m
Heart
Left lung
Nasalcavity
Pharynx
Larynx
Diaphragm
Bronchiole
Bronchus
Right lung
Trachea
Esophagus
Figure 42.23
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
Air inhaled Air exhaled
INHALATIONDiaphragm contracts
(moves down)
EXHALATIONDiaphragm relaxes
(moves up)
Diaphragm
Lung
Rib cage expands asrib muscles contract
Rib cage gets smaller asrib muscles relax
Figure 42.24
Negative pressure breathing
The volume increases by the diaphragm moving down and the rib cage moving up and out
Negative pressure breathing
The volume increases by the diaphragm moving down and the rib cage moving up and out
Higher air pressure forces air in
Higher air pressure forces air in
Lower pressureLower pressure
Tidal volume is a normal breath
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
Tidal volume is a normal breath
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
INHALATIONAir sacs fill
EXHALATIONAir sacs empty; lungs fill
Anteriorair sacs
Trachea
Lungs LungsPosteriorair sacs
Air Air
1 mm
Air tubes(parabronchi)in lung
Figure 42.25
Parabronchi allow for one way flow of air through lungs
Parabronchi allow for one way flow of air through lungs
• 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
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
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
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
Heme group Iron atom
O2 loadedin lungs
O2 unloadedIn tissues
Polypeptide chain
O2
O2
Figure 42.28
One molecule of hemoglobin has 4 prosthetic heme groups, allowing it to bind to 4 O2 molecules
Cooperativity
-the binding of one O2 allows the next O2 to bind easier
One molecule of hemoglobin has 4 prosthetic heme groups, allowing it to bind to 4 O2 molecules
Cooperativity
-the binding of one O2 allows the next O2 to bind easier
• 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
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
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 pHlowers the affinity of hemo-globin for O2, an effectcalled the Bohr shift.
• Because CO2 reacts with water to form carbonic acid, an active tissue will lower the pH of its surroundingsand induce hemoglobinto release more oxygen.
Fig. 42.28b
Higher temps right shift curve making it easier to dump Oxygen
Higher temps right shift curve making it easier to dump Oxygen
Animals with a high metabolic rate have a right shifted curve
Animals with a high metabolic rate have a right shifted curve
Most CO2 travels in the plasma as a bicarbonate ion
Most CO2 travels in the plasma as a bicarbonate ion
Hb acts as a buffer in picking up H+
Hb acts as a buffer in picking up H+
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.
• 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.
Deep-diving air-breathers stockpile oxygen and deplete it slowly
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.
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