circulation and gas exchange chapter 42. trading with the environment every organism must exchange...
TRANSCRIPT
Circulation and Gas Exchange
Chapter 42
Trading with the Environment Every organism must exchange materials
with its environment And this exchange ultimately occurs at the
cellular level In unicellular organisms
These exchanges occur directly with the environment
For most of the cells making up multicellular organisms Direct exchange with the environment is not
possible
The feathery gills projecting from a salmon Are an example of a specialized
exchange system found in animals
Figure 42.1
Circulatory System
Internal transport systemDistributes nutrientsRemoves wastesRepairs tissuesHelps fight infections
In circulation… What needs to be transported
nutritive nutrients fuels from digestive system
respiratory O2 & CO2 from & to gas exchange systems: lungs, gills
excretory waste products from cells
water, salts, nitrogenous wastes (urea) protection
blood clotting immune defenses
white blood cells & others patrolling body regulation
hormones
Invertebrate Circulation Simple Diffusion
Body cavity 2-cell layers think all cells within easy reach of fluid use gastrovascular cavity for exchange
Cnidarians
Hydra
Circulatory systemsAll animals have:
circulatory fluid = bloodtubes = blood vesselsmuscular pump = heart
Open or Closed Systems
Open circulatory system Taxonomy
invertebrates insects,
arthropods, mollusks
Structure no distinction
between blood & extracellular (interstitial) fluid hemolymph
Closed circulatory system Taxonomy
invertebrates earthworms, squid,
octopusesvertebrates
Structureblood confined to vessels
& separate from interstitial fluid
1 or more hearts large vessels to smaller
vessels material diffuses
between vessels & interstitial fluid
Vertebrate Circulatory System Closed system
number of heart chambers differs
What’s the adaptive value of a 4 chamber heart?4 chamber heart is double pump =
separates oxygen-rich & oxygen-poor blood
Survey of Vertebrate Circulation
Humans and other vertebrates have a closed circulatory system Often called the cardiovascular system
Blood flows in a closed cardiovascular system Consisting of blood vessels and a two- to four-
chambered heart A powerful four-chambered heart
Was an essential adaptation of the endothermic way of life characteristic of mammals and birds
Fishes
A fish heart has two main chambers One ventricle and one atrium
Blood pumped from the ventricle Travels to the gills, where it picks up O2
and disposes of CO2
Amphibians
Frogs and other amphibians Have a three-chambered heart, with
two atria and one ventricle The ventricle pumps blood into a
forked artery That splits the ventricle’s output into
the pulmocutaneous circuit and the systemic circuit
Reptiles (Except Birds)
Reptiles have double circulation With a pulmonary circuit (lungs) and a
systemic circuit Turtles, snakes, and lizards
Have a three-chambered heart
Mammals and Birds
In all mammals and birds The ventricle is completely divided into
separate right and left chambers The left side of the heart pumps and
receives only oxygen-rich blood While the right side receives and
pumps only oxygen-poor blood
Evolution of vertebrate circulatory system
fish amphibian reptiles birds & mammals
A A
VV V VV
A AAAA
V
2 chamber 3 chamber 3 chamber 4 chamber
heart structure & increasing body size
Driving evolution of CV systems
Metabolic rateendothermy = higher
metabolic rate greater need for energy,
fuels, O2, waste removal more complex circulatory
system more powerful hearts
The Cardiac Cycle
A rhythmic cycle the heart contracts and relaxes
Systole contraction, or pumping, phase of the cycle
Diastole relaxation, or filling, phase of the cycle
Figure 42.7
Semilunarvalvesclosed
AV valvesopen
AV valvesclosed
Semilunarvalvesopen
Atrial and ventricular diastole
1
Atrial systole; ventricular diastole
2
Ventricular systole; atrial diastole
3
0.1 sec
0.3 sec0.4 sec
Pulse and Cardiac Output
The heart rate, also called the pulse Is the number of beats per minute
The cardiac output Is the volume of blood pumped into the
systemic circulation per minute
Maintaining the Heart’s Rhythmic Beat
Some cardiac muscle cells are self-excitable they contract without any signal from the nervous system
A region of the heart called the sinoatrial (SA) node, or pacemaker Sets the rate and timing at which all cardiac
muscle cells contract Impulses from the SA node
Travel to the atrioventricular (AV) node At the AV node, the impulses are delayed
And then travel to the Purkinje fibers that make the ventricles contract
Electrocardiograms(ECG or EKG) Recorded impulses that travel during
the cardiac cycle
Figure 42.8
SA node(pacemaker)
AV node Bundlebranches
Heartapex
Purkinjefibers
2 Signals are delayedat AV node.
1 Pacemaker generates wave of signals to contract.
3 Signals passto heart apex.
4 Signals spreadThroughoutventricles.
ECG
The control of heart rhythm
Blood Vessel Structure and Function
The “infrastructure” of the circulatory system Is its network of blood vessels
Blood Vessels The “infrastructure” of the circulatory
system Is its network of blood vessels
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 Vessels
Structural differences in arteries, veins, and capillaries Correlate with their different functions Arteries have thicker walls
To accommodate the high pressure of blood pumped from the heart
In the thinner-walled veins Blood flows back to the heart mainly as a result
of muscle action
Blood Pressure The hydrostatic pressure that blood exerts
against the wall of a vessel Systolic pressure
Is the pressure in the arteries during ventricular systole
Is the highest pressure in the arteries Diastolic pressure
Is the pressure in the arteries during diastole Is lower than systolic pressure
Blood Pressure
Figure 42.13 The movement of fluid between capillaries and the interstitial fluid
Figure 43.4 The human lymphatic system
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
Another important class of solutes is the plasma proteins Which influence blood pH, osmotic pressure,
and viscosity Various types of plasma proteins
Function in lipid transport, immunity, and blood clotting
Cellular Elements
Suspended in blood plasma are two classes of cells Red blood cells, which transport oxygen,
most numerous White blood cells, which function in defense
A third cellular element, platelets Are fragments of cells that are involved in
clotting
Figure 42.14 The composition of mammalian blood
Figure 42.15 Differentiation of blood cells
Leukocytes
The blood contains five major types of white blood cells, or leukocytes Monocytes, neutrophils, basophils,
eosinophils, and lymphocytes, which function in defense by phagocytizing bacteria and debris or by producing antibodies
Stem Cells and the Replacement of Cellular Elements
The cellular elements of blood wear out And are replaced constantly throughout
a person’s life
Erythrocytes, leukocytes, and platelets all develop from a common source
A single population of cells called pluripotent stem cells in the red marrow of bones
B cells T cells
Lymphoidstem cells
Pluripotent stem cells(in bone marrow)
Myeloidstem cells
Erythrocytes
Platelets Monocytes
Neutrophils
Eosinophils
Basophils
Lymphocytes
Figure 42.16
Blood Clotting When the endothelium of a blood vessel is
damaged The clotting mechanism begins
Plateletplug
Collagen fibers
Platelet releases chemicalsthat make nearby platelets sticky
Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)
Prothrombin Thrombin
Fibrinogen Fibrin5 µm
Fibrin clot Red blood cell
The clotting process begins when the endothelium of a vessel is damaged, exposing connective tissue in the vessel wall to blood. Plateletsadhere to collagen fibers in the connective tissue and release a substance thatmakes nearby platelets sticky.
1 The platelets form a plug that providesemergency protectionagainst blood loss.
2This seal is reinforced by a clot of fibrin when vessel damage is severe. Fibrin is formed via amultistep process: Clotting factors released fromthe clumped platelets or damaged cells mix withclotting factors in the plasma, forming an activation cascade that converts a plasma proteincalled prothrombin to its active form, thrombin.Thrombin itself is an enzyme that catalyzes the final step of the clotting process, the conversion of fibrinogen to fibrin. The threads of fibrin become interwoven into a patch (see colorized SEM).
3
Figure 42.17
Cardiovascular Disease
Cardiovascular diseases Are disorders of the heart and the
blood vessels Account for more than half the deaths
in the United States
One type of cardiovascular disease, atherosclerosis Is caused by the buildup of cholesterol within arteries
Figure 42.18a, b
(a) Normal artery (b) Partly clogged artery50 µm 250 µm
Smooth muscleConnective tissue Endothelium Plaque
Hypertension, or high blood pressure Promotes atherosclerosis and increases
the risk of heart attack and stroke A heart attack
Is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries
A stroke Is the death of nervous tissue in the
brain, usually resulting from rupture or blockage of arteries in the head
Gas Exchange Supplies oxygen for cellular respiration
and disposes of carbon dioxide
Figure 42.19
Organismal level
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO2
Gills in Aquatic Animals
Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases Between their cells and the respiratory
medium, either air or water
Gills in Aquatic Animals
Gills are outfoldings of the body surface Specialized for gas exchange
In some Invertebrates
The gills have a simple shape and are distributed over much of the body (a) Sea star. The gills of a sea
star are simple tubular projections of the skin. The hollow core of each gillis an extension of the coelom(body cavity). Gas exchangeoccurs by diffusion across thegill surfaces, and fluid in thecoelom circulates in and out ofthe gills, aiding gas transport. The surfaces of a sea star’s tube feet also function in gas exchange.
Gills
Tube foot
Coelom
Figure 42.20a
Segmented Worms Have flaplike gills extend from
each segment of their body
Figure 42.20b
(b) Marine worm. Many polychaetes (marine worms of the phylum Annelida) have a pair of flattened appendages called parapodia on each body segment. The parapodia serve as gillsand also function incrawling and swimming.
Gill
Parapodia
Gills of clams, crayfish, and many other animals
Are restricted to a local body region
Figure 42.20c, d
(d) Crayfish. Crayfish and other crustaceanshave long, feathery gills covered by the exoskeleton. Specialized body appendagesdrive water over the gill surfaces.
(c) Scallop. The gills of a scallop are long, flattened plates that project from themain body mass inside the hard shell.Cilia on the gills circulate water around the gill surfaces.
Gills
Gills
Fish Gills
Countercurrent exchange
Figure 42.21
Gill arch
Water flow Operculum
Gill arch
Blood vessel
Gillfilaments
Oxygen-poorblood
Oxygen-richblood
Water flowover lamellaeshowing % O2
Blood flowthrough capillariesin lamellaeshowing % O2
Lamella
100%
40%
70%
15%
90%
60%
30% 5%
O2
Figure 42.22a
Tracheae
Air sacs
Spiracle
(a) The respiratory system of an insect consists of branched internaltubes that deliver air directly to body cells. Rings of chitin reinforcethe largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid(blue-gray). When the animal is active and is using more O2, most ofthe fluid is withdrawn into the body. This increases the surface area of air in contact with cells.
Tracheal Systems in Insects Consists of tiny branching tubes that
penetrate the body
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
Lungs Restricted to one location
Human Anatomy
Nares Pharynx Larynx/Epiglottis Glottis Trachea Bronchi Bronchioles Alveoli Lungs Diaphragm
Microscopic Anatomy Bronchioles Alveoli Blood Supply
Pulmonary A/VBronchial A/V
Mechanism of Breathing
When you breathe in . . .
Vagus Nerve
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 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
Autonomic Breathing Control
Vagus Nerve Medulla sets
rhythm
Pons moderates rhythm
Chemoreceptors Baroreceptors
Carotid, aorta
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
A gas always diffuses from a region of higher partial pressure To a region of lower partial pressure
In the lungs and in the tissues O2 and CO2 diffuse from where their
partial pressures are higher to where they are lower
Inhaled air Exhaled air
160 0.2O2 CO2
O2 CO2
O2 CO2
O2 CO2 O2 CO2
O2 CO2 O2 CO2
O2 CO2
40 45
40 45
100 40
104 40
104 40
120 27
CO2O2
Alveolarepithelialcells
Pulmonaryarteries
Blood enteringalveolar
capillaries
Blood leavingtissue
capillaries
Blood enteringtissue
capillaries
Blood leaving
alveolar capillaries
CO2O2
Tissue capillaries
Heart
Alveolar capillaries
of lung
<40 >45
Tissue cells
Pulmonaryveins
Systemic arteriesSystemic
veinsO2
CO2
O2
CO 2
Alveolar spaces
12
43
Figure 42.27
Respiratory Pigments
Respiratory pigments Are proteins that transport oxygen Greatly increase the amount of oxygen
that blood can carry
Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body
Transport of Oxygen98.5% bound to hemoglobin
1.5% dissolved in plasma
Carbon Dioxide Transport
Hemoglobin also helps transport CO2
And assists in buffering Carbon from respiring cells
Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs
Figure 42.30
Tissue cell
CO2Interstitialfluid
CO2 producedCO2 transportfrom tissues
CO2
CO2
Blood plasmawithin capillary Capillary
wall
H2O
Redbloodcell
HbCarbonic acidH2CO3
HCO3–
H++Bicarbonate
HCO3–
Hemoglobinpicks up
CO2 and H+
HCO3–
HCO3– H++
H2CO3Hb
Hemoglobinreleases
CO2 and H+
CO2 transportto lungs
H2O
CO2
CO2
CO2
CO2
Alveolar space in lung
2
1
34
5 6
7
8
9
10
11
To lungs
Carbon dioxide produced bybody tissues diffuses into the interstitial fluid and the plasma.
Over 90% of the CO2 diffuses into red blood cells, leaving only 7%in the plasma as dissolved CO2.
Some CO2 is picked up and transported by hemoglobin.
However, most CO2 reacts with water in red blood cells, forming carbonic acid (H2CO3), a reaction catalyzed bycarbonic anhydrase contained. Withinred blood cells.
Carbonic acid dissociates into a biocarbonate ion (HCO3
–) and a hydrogen ion (H+).
Hemoglobin binds most of the H+ from H2CO3 preventing the H+ from acidifying the blood and thuspreventing the Bohr shift.
CO2 diffuses into the alveolarspace, from which it is expelledduring exhalation. The reductionof CO2 concentration in the plasmadrives the breakdown of H2CO3 Into CO2 and water in the red bloodcells (see step 9), a reversal of the reaction that occurs in the tissues (see step 4).
Most of the HCO3– diffuse
into the plasma where it is carried in the bloodstream to the lungs.
In the HCO3– diffuse
from the plasma red blood cells, combining with H+ released from hemoglobin and forming H2CO3.
Carbonic acid is converted back into CO2 and water.
CO2 formed from H2CO3 is unloadedfrom hemoglobin and diffuses into the interstitial fluid.
1
2
3
4
5
6
7
8
9
10
11
Elite Animal Athletes
Migratory and diving mammals Have evolutionary adaptations that
allow them to perform extraordinary feats
The Ultimate Endurance Runner The extreme O2 consumption of the
antelope-like pronghorn Underlies its ability to run at high speed over
long distances
Figure 42.31
Diving Mammals
Deep-diving air breathers Stockpile O2 and deplete it slowly