Biology "B" / Ch42

LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures byErin Barley

Kathleen Fitzpatrick

Circulation and Gas Exchange

Chapter 42

Overview: Trading Places

• Every organism must exchange materials with its environment

• Exchanges ultimately occur at the cellular level by crossing the plasma membrane

• In unicellular organisms, these exchanges occur directly with the environment


• For most cells making up multicellular organisms, direct exchange with the environment is not possible

• Gills are an example of a specialized exchange system in animals

– O2 diffuses from the water into blood vessels

– CO2 diffuses from blood into the water

• Internal transport and gas exchange are functionally related in most animals


Figure 42.1

Concept 42.1: Circulatory systems link exchange surfaces with cells throughout the body

• Diffusion time is proportional to the square of the distance

• Diffusion is only efficient over small distances• In small and/or thin animals, cells can exchange

materials directly with the surrounding medium• In most animals, cells exchange materials with the

environment via a fluid-filled circulatory system


Gastrovascular Cavities

• Some animals lack a circulatory system• Some cnidarians, such as jellies, have elaborate

gastrovascular cavities• A gastrovascular cavity functions in both digestion

and distribution of substances throughout the body• The body wall that encloses the gastrovascular

cavity is only two cells thick• Flatworms have a gastrovascular cavity and a

large surface area to volume ratio


Figure 42.2

Circularcanal

Mouth

Radial canals 5 cm

(a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm

Gastrovascularcavity

Mouth

Pharynx2 mm

Figure 42.2a

Circularcanal

Mouth

Radial canals 5 cm

(a) The moon jelly Aurelia, a cnidarian

Figure 42.2b

(b) The planarian Dugesia, a flatworm

Gastrovascularcavity

Mouth

Pharynx2 mm

Evolutionary Variation in Circulatory Systems

• A circulatory system minimizes the diffusion distance in animals with many cell layers


General Properties of Circulatory Systems

• A circulatory system has– A circulatory fluid

– A set of interconnecting vessels

– A muscular pump, the heart

• The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes

• Circulatory systems can be open or closed, and vary in the number of circuits in the body


Open and Closed Circulatory Systems

• In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system

• In an open circulatory system, there is no distinction between blood and interstitial fluid, and this general body fluid is called hemolymph


Figure 42.3

(a) An open circulatory system

Heart

Hemolymph in sinusessurrounding organs

Pores

Tubular heart

Dorsalvessel

(main heart)

Auxiliaryhearts

Small branchvessels ineach organ

Ventral vessels

Blood

Interstitial fluid

Heart

(b) A closed circulatory system

Figure 42.3a

(a) An open circulatory system

Heart

Hemolymph in sinusessurrounding organs

Pores

Tubular heart

• In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid

• Closed systems are more efficient at transporting circulatory fluids to tissues and cells

• Annelids, cephalopods, and vertebrates have closed circulatory systems


Figure 42.3b

(b) A closed circulatory system

Dorsalvessel

(main heart)

Auxiliaryhearts

Small branchvessels ineach organ

Ventral vessels

Blood

Interstitial fluid

Heart

Organization of Vertebrate Circulatory Systems

• Humans and other vertebrates have a closed circulatory system called the cardiovascular system

• The three main types of blood vessels are arteries, veins, and capillaries

• Blood flow is one way in these vessels


• Arteries branch into arterioles and carry blood away from the heart to capillaries

• Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid

• Venules converge into veins and return blood from capillaries to the heart

© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.

• Arteries and veins are distinguished by the direction of blood flow, not by O2 content

• Vertebrate hearts contain two or more chambers• Blood enters through an atrium and is pumped

out through a ventricle


Single Circulation

• Bony fishes, rays, and sharks have single circulation with a two-chambered heart

• In single circulation, blood leaving the heart passes through two capillary beds before returning


Figure 42.4

(a) Single circulation (b) Double circulation

Artery

Heart:

Atrium (A)

Ventricle (V)

Vein

Gillcapillaries

Bodycapillaries

Key

Oxygen-rich blood

Oxygen-poor blood

Systemic circuit

Systemiccapillaries

Right Left

A A

VV

Lungcapillaries

Pulmonary circuit

Figure 42.4a (a) Single circulation

Artery

Heart:

Atrium (A)

Ventricle (V)

Vein

Gillcapillaries

Bodycapillaries

Key

Oxygen-rich blood

Oxygen-poor blood

Double Circulation

• Amphibian, reptiles, and mammals have double circulation

• Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart


Figure 42.4b(b) Double circulation

Systemic circuit

Systemiccapillaries

Right Left

A A

VV

Lungcapillaries

Pulmonary circuit

Key

Oxygen-rich blood

Oxygen-poor blood

• In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs

• In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin

• Oxygen-rich blood delivers oxygen through the systemic circuit

• Double circulation maintains higher blood pressure in the organs than does single circulation


Adaptations of Double Circulatory Systems• Hearts vary in different vertebrate groups


Amphibians• Frogs and other amphibians have a three-

chambered heart: 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

• When underwater, blood flow to the lungs is nearly shut off


Amphibians

Pulmocutaneous circuit

Lungand skincapillaries

Atrium(A)

Atrium(A)

LeftRight

Ventricle (V)

Systemiccapillaries

Systemic circuit

Key

Oxygen-rich bloodOxygen-poor blood

Figure 42.5a

Reptiles (Except Birds)• Turtles, snakes, and lizards have a three-

chambered heart: two atria and one ventricle• In alligators, caimans, and other crocodilians a

septum divides the ventricle • Reptiles have double circulation, with a pulmonary

circuit (lungs) and a systemic circuit


Figure 42.5b

Reptiles (Except Birds)

Pulmonary circuit

Systemic circuit

Systemiccapillaries

Incompleteseptum

Leftsystemicaorta

LeftRight

Rightsystemicaorta

A

V

Lungcapillaries

Atrium(A)

Ventricle(V)

Key


Mammals and Birds• Mammals and birds have a four-chambered heart

with two atria and two ventricles• The left side of the heart pumps and receives only

oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood

• Mammals and birds are endotherms and require more O2 than ectotherms


Systemic circuit

Lungcapillaries

Pulmonary circuit

A

VLeftRight

Systemiccapillaries

Mammals and Birds

Atrium(A)

Ventricle(V)

Key


Figure 42.5c

Figure 42.5

Amphibians Reptiles (Except Birds)

Pulmocutaneous circuit Pulmonary circuit

Lungand skincapillaries

Atrium(A)

Atrium(A)

LeftRight

Ventricle (V)

Systemiccapillaries

Systemic circuit Systemic circuit Systemic circuit

Systemiccapillaries

IncompleteseptumIncompleteseptum

Leftsystemicaorta

LeftRight

Rightsystemicaorta

A A

V V

Lungcapillaries

Lungcapillaries

Pulmonary circuit

A AV V

LeftRight

Systemiccapillaries

Key


Mammals and Birds

Concept 42.2: Coordinated cycles of heart contraction drive double circulation in mammals

• The mammalian cardiovascular system meets the body’s continuous demand for O2


Mammalian Circulation

• Blood begins its flow with the right ventricle pumping blood to the lungs

• In the lungs, the blood loads O2 and unloads CO2

• Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped through the aorta to the body tissues by the left ventricle

• The aorta provides blood to the heart through the coronary arteries


• Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs)

• The superior vena cava and inferior vena cava flow into the right atrium


Animation: Path of Blood Flow in Mammals


Animation: Path of Blood Flow in MammalsRight-click slide / select “Play”

Superior vena cava

Pulmonaryartery

Capillariesof right lung

Pulmonaryvein

Aorta

Inferiorvena cava

Right ventricle

Capillaries ofabdominal organsand hind limbs

Right atrium

Aorta

Left ventricle

Left atrium

Pulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Figure 42.6

The Mammalian Heart: A Closer Look

• A closer look at the mammalian heart provides a better understanding of double circulation


Figure 42.7

Pulmonary artery

Rightatrium

Semilunarvalve

Atrioventricularvalve

Rightventricle

Leftventricle

Atrioventricularvalve

Semilunarvalve

Leftatrium

Pulmonaryartery

Aorta

• The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle

• The contraction, or pumping, phase is called systole

• The relaxation, or filling, phase is called diastole


Figure 42.8-1

Atrial andventricular diastole

0.4sec

1

Figure 42.8-2


Atrial systole and ventricular diastole

0.1sec

0.4sec

2

1

Figure 42.8-3


Atrial systole and ventricular diastole

Ventricular systole and atrialdiastole

0.1sec

0.4sec

0.3 sec

2

1

3

• The heart rate, also called the pulse, is the number of beats per minute

• The stroke volume is the amount of blood pumped in a single contraction

• The cardiac output is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume


• Four valves prevent backflow of blood in the heart• The atrioventricular (AV) valves separate each

atrium and ventricle• The semilunar valves control blood flow to the

aorta and the pulmonary artery


• The “lub-dup” sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves

• Backflow of blood through a defective valve causes a heart murmur


Maintaining the Heart’s Rhythmic Beat

• Some cardiac muscle cells are self-excitable, meaning they contract without any signal from the nervous system

• The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which cardiac muscle cells contract

• Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)


Figure 42.9-1

SA node(pacemaker)

ECG

1

Figure 42.9-2

SA node(pacemaker)

AVnode

ECG

1 2

Figure 42.9-3

SA node(pacemaker)

AVnode Bundle

branches Heartapex

ECG

1 2 3

Figure 42.9-4

SA node(pacemaker)

AVnode Bundle

branches Heartapex

Purkinjefibers

ECG

1 2 3 4

• 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


• The pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions

• The sympathetic division speeds up the pacemaker

• The parasympathetic division slows down the pacemaker

• The pacemaker is also regulated by hormones and temperature


Concept 42.3: Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels

• The physical principles that govern movement of water in plumbing systems also influence the functioning of animal circulatory systems


Blood Vessel Structure and Function

• A vessel’s cavity is called the central lumen• The epithelial layer that lines blood vessels is

called the endothelium• The endothelium is smooth and minimizes

resistance


Figure 42.10 Artery

Red blood cells

Endothelium

Artery

Smoothmuscle

Connectivetissue

Capillary

Valve

Vein

Vein

Basal lamina

Endothelium

Smoothmuscle

Connectivetissue

100 µm

LM

Venule

15 µ

mL

M

Arteriole

Red blood cell

Capillary

Figure 42.10a

Endothelium

Artery

Smoothmuscle

Connectivetissue

Capillary

Valve

Vein

Basal lamina

Endothelium

Smoothmuscle

Connectivetissue

VenuleArteriole

Figure 42.10b

Artery

Red blood cells

Vein

100 µm

LM

Figure 42.10c

15

µm

LM

Red blood cell

Capillary

• Capillaries have thin walls, the endothelium plus its basal lamina, to facilitate the exchange of materials

• Arteries and veins have an endothelium, smooth muscle, and connective tissue

• Arteries have thicker walls than veins 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 Flow Velocity

• Physical laws governing movement of fluids through pipes affect blood flow and blood pressure

• Velocity of blood flow is slowest in the capillary beds, as a result of the high resistance and large total cross-sectional area

• Blood flow in capillaries is necessarily slow for exchange of materials


Figure 42.11

Aorta

Arterie

sArte

riole

s

Capill

arie

sVen

ules

Veins

Venae

cava

e

Systolicpressure

Diastolicpressure

020406080

100120

01020304050

Pre

ss

ure

(mm

Hg

)V

elo

cit

y(c

m/s

ec

)A

rea

(c

m2)

01,0002,0003,0004,0005,000

Blood Pressure

• Blood flows from areas of higher pressure to areas of lower pressure

• Blood pressure is the pressure that blood exerts against the wall of a vessel

• In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost


Changes in Blood Pressure During the Cardiac Cycle

• Systolic pressure is the pressure in the arteries during ventricular systole; it is the highest pressure in the arteries

• Diastolic pressure is the pressure in the arteries during diastole; it is lower than systolic pressure

• A pulse is the rhythmic bulging of artery walls with each heartbeat


Regulation of Blood Pressure

• Blood pressure is determined by cardiac output and peripheral resistance due to constriction of arterioles

• Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood pressure

• Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall


• Vasoconstriction and vasodilation help maintain adequate blood flow as the body’s demands change

• Nitric oxide is a major inducer of vasodilation• The peptide endothelin is an important inducer of

vasoconstriction


Blood Pressure and Gravity

• Blood pressure is generally measured for an artery in the arm at the same height as the heart

• Blood pressure for a healthy 20 year old at rest is 120 mm Hg at systole and 70 mm Hg at diastole


Blood pressure reading: 120/70

120

70

Soundsstop

Soundsaudible instethoscope

120

Arteryclosed

1 2 3

Figure 42.12

• Fainting is caused by inadequate blood flow to the head

• Animals with longer necks require a higher systolic pressure to pump blood a greater distance against gravity

• Blood is moved through veins by smooth muscle contraction, skeletal muscle contraction, and expansion of the vena cava with inhalation

• One-way valves in veins prevent backflow of blood


Direction of blood flowin vein (toward heart) Valve (open)

Skeletal muscle

Valve (closed)

Figure 42.13

Capillary Function

• Blood flows through only 5−10% of the body’s capillaries at a time

• Capillaries in major organs are usually filled to capacity

• Blood supply varies in many other sites


• Two mechanisms regulate distribution of blood in capillary beds

– Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel

– Precapillary sphincters control flow of blood between arterioles and venules

• Blood flow is regulated by nerve impulses, hormones, and other chemicals


Figure 42.14Precapillarysphincters

Thoroughfarechannel

Arteriole

CapillariesVenule

(a) Sphincters relaxed

Arteriole Venule

(b) Sphincters contracted

• The exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries

• The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end

• Most blood proteins and all blood cells are too large to pass through the endothelium


Figure 42.15

INTERSTITIALFLUID Net fluid movement out

Bloodpressure

Osmoticpressure

Arterial endof capillary Direction of blood flow

Venous endof capillary

Body cell

Fluid Return by the Lymphatic System

• The lymphatic system returns fluid that leaks out from the capillary beds

• Fluid, called lymph, reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system

• The lymphatic system drains into veins in the neck• Valves in lymph vessels prevent the backflow of

fluid


• Lymph nodes are organs that filter lymph and play an important role in the body’s defense

• Edema is swelling caused by disruptions in the flow of lymph


Figure 42.16

Concept 42.4: Blood components contribute to exchange, transport, and defense

• With open circulation, the fluid that is pumped comes into direct contact with all cells

• The closed circulatory systems of vertebrates contain blood, a specialized connective tissue


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


Figure 42.17

Plasma 55%

Constituent Major functions

Water

Ions (bloodelectrolytes)SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Solvent forcarrying othersubstances

Osmotic balance,pH buffering,and regulationof membranepermeablity

Plasma proteinsOsmotic balance,pH buffering

Albumin

Fibrinogen

Immunoglobulins(antibodies)

Clotting

Defense

Substances transported by blood

NutrientsWaste productsRespiratory gasesHormones

Separatedbloodelements

Basophils

Neutrophils Monocytes

Lymphocytes

Eosinophils

Platelets

Erythrocytes (red blood cells) 5–6 million

250,000–400,000 Bloodclotting

Transportof O2 and

some CO2

Defense andimmunity

FunctionsNumber per µL(mm3) of blood

Cell type

Cellular elements 45%

Leukocytes (white blood cells) 5,000–10,000

Plasma 55%

Constituent Major functions

Water

Ions (bloodelectrolytes)SodiumPotassiumCalciumMagnesiumChlorideBicarbonate

Solvent forcarrying othersubstances

Osmotic balance,pH buffering,and regulationof membranepermeablity

Plasma proteinsOsmotic balance, pH bufferingAlbumin

FibrinogenImmunoglobulins (antibodies)

ClottingDefense

Substances transported by blood

NutrientsWaste products


Respiratory gasesHormones

Figure 42.17a


Basophils

NeutrophilsMonocytes

Lymphocytes

Eosinophils

Platelets

Erythrocytes (red blood cells) 5–6 million

250,000–400,000 Bloodclotting

Transportof O2 andsome CO2

Defense andimmunity

FunctionsNumber per µL(mm3) of blood

Cell type

Cellular elements 45%

Leukocytes (white blood cells) 5,000–10,000

Figure 42.17b

Plasma

• Blood plasma is about 90% water• Among its solutes are inorganic salts in the form of

dissolved ions, sometimes called electrolytes• Another important class of solutes is the plasma

proteins, which influence blood pH, osmotic pressure, and viscosity

• Various plasma proteins function in lipid transport, immunity, and blood clotting


Cellular Elements

• Suspended in blood plasma are two types of cells– Red blood cells (erythrocytes) transport oxygen O2

– White blood cells (leukocytes) function in defense

• Platelets, a third cellular element, are fragments of cells that are involved in clotting


• Red blood cells, or erythrocytes, are by far the most numerous blood cells

• They contain hemoglobin, the iron-containing protein that transports O2

• Each molecule of hemoglobin binds up to four molecules of O2

• In mammals, mature erythrocytes lack nuclei and mitochondria

Erythrocytes


• Sickle-cell disease is caused by abnormal hemoglobin proteins that form aggregates

• The aggregates can deform an erythrocyte into a sickle shape

• Sickled cells can rupture, or block blood vessels


Leukocytes• There are five major types of white blood cells, or

leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes

• They function in defense by phagocytizing bacteria and debris or by producing antibodies

• They are found both in and outside of the circulatory system


Platelets• Platelets are fragments of cells and function in

blood clotting


Blood Clotting

• Coagulation is the formation of a solid clot from liquid blood

• A cascade of complex reactions converts inactive fibrinogen to fibrin, forming a clot

• A blood clot formed within a blood vessel is called a thrombus and can block blood flow


Figure 42.18

Collagen fibers

1 2 3

PlateletPlateletplug

Fibrinclot

Fibrin clot formation

Red blood cell 5 µm

Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)

Enzymatic cascade

Prothrombin Thrombin

Fibrinogen Fibrin

+

Collagen fibers

1

PlateletPlateletplug

Fibrinclot

Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)

Enzymatic cascade

Prothrombin Thrombin

Fibrinogen Fibrin

+

Fibrin clotformation

2 3

Figure 42.18a

Figure 42.18b

Fibrinclot Red blood cell 5 µm

Stem Cells and the Replacement of Cellular Elements

• The cellular elements of blood wear out and are being replaced constantly

• Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis

• The hormone erythropoietin (EPO) stimulates erythrocyte production when O2 delivery is low


Stem cells(in bone marrow)

Myeloidstem cells

Lymphoidstem cells

B cells T cells

Lymphocytes

ErythrocytesNeutrophils

Basophils

EosinophilsPlateletsMonocytes

Figure 42.19

Cardiovascular Disease

• Cardiovascular diseases are disorders of the heart and the blood vessels

• Cardiovascular diseases account for more than half the deaths in the United States

• Cholesterol, a steroid, helps maintain membrane fluidity


• Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production

• High-density lipoprotein (HDL) scavenges cholesterol for return to the liver

• Risk for heart disease increases with a high LDL to HDL ratio

• Inflammation is also a factor in cardiovascular disease


Atherosclerosis, Heart Attacks, and Stroke

• One type of cardiovascular disease, atherosclerosis, is caused by the buildup of plaque deposits within arteries


Lumen of artery

Smoothmuscle

EndotheliumPlaque

Smoothmusclecell

T lymphocyte

Extra-cellularmatrix

Foam cellMacrophage

Plaque rupture

LDL

CholesterolFibrous cap

1 2

43

Figure 42.20

• A heart attack, or myocardial infarction, is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries

• Coronary arteries supply oxygen-rich blood to the heart muscle

• A stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head

• Angina pectoris is caused by partial blockage of the coronary arteries and results in chest pains


Risk Factors and Treatment of Cardiovascular Disease

• A high LDL to HDL ratio increases the risk of cardiovascular disease

• The proportion of LDL relative to HDL can be decreased by exercise, not smoking, and avoiding foods with trans fats

• Drugs called statins reduce LDL levels and risk of heart attacks


Figure 42.21

Individuals with two functional copies ofPCSK9 gene (control group)

Plasma LDL cholesterol (mg/dL)

Individuals with an inactivating mutation inone copy of PCSK9 gene

Plasma LDL cholesterol (mg/dL)

Average = 63 mg/dLAverage = 105 mg/dL30

20

10

00 50 100 150 200 250 300 0

0

10

20

30

50 100 150 200 250 300

Per

cen

t o

f in

div

idu

als

RESULTS

Per

cen

t o

f in

div

idu

als

• Inflammation plays a role in atherosclerosis and thrombus formation

• Aspirin inhibits inflammation and reduces the risk of heart attacks and stroke

• Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke

• Hypertension can be reduced by dietary changes, exercise, and/or medication


Concept 42.5: Gas exchange occurs across specialized respiratory surfaces

• Gas exchange supplies O2 for cellular respiration and disposes of CO2


Partial Pressure Gradients in Gas Exchange

• A gas diffuses from a region of higher partial pressure to a region of lower partial pressure

• Partial pressure is the pressure exerted by a particular gas in a mixture of gases

• Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure


Respiratory Media

• Animals can use air or water as a source of O2, or respiratory medium

• In a given volume, there is less O2 available in water than in air

• Obtaining O2 from water requires greater efficiency than air breathing


Respiratory Surfaces

• Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water

• Gas exchange across respiratory surfaces takes place by diffusion

• Respiratory surfaces vary by animal and can include the outer surface, skin, gills, tracheae, and lungs


Gills in Aquatic Animals

• Gills are outfoldings of the body that create a large surface area for gas exchange


Figure 42.22

Parapodium(functions as gill)

(a) Marine worm (b) Crayfish

GillsGills

Tube foot

(c) Sea star

Coelom

Figure 42.22a

Parapodium (functions as gill)

(a) Marine worm

Figure 42.22b

(b) Crayfish

Gills

Figure 42.22c

Gills

Tube foot

(c) Sea star

Coelom

• Ventilation moves the respiratory medium over the respiratory surface

• Aquatic animals move through water or move water over their gills for ventilation

• Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets


Figure 42.23

Gillarch

O2-poor blood

O2-rich blood

Bloodvessels

Gill arch

OperculumWaterflow

Water flowBlood flow

Countercurrent exchange

PO (mm Hg) in water2

150

PO (mm Hg)

in blood2

120 90 60 30

140 110 80 50 20Net diffu-sion of O2

Lamella

Gill filaments

Gillarch

OperculumWaterflow

Bloodvessels

Gill arch

Gill filaments

Figure 42.23a

O2-poor blood

Water flowBlood flow

Countercurrent exchange

PO (mm Hg) in water2

150

PO (mm Hg)

in blood2

140Net diffu-sion of O2

Lamella

O2-rich blood

120 90 60 30

110 80 50 20

Figure 42.23b

Tracheal Systems in Insects

• The tracheal system of insects consists of tiny branching tubes that penetrate the body

• The tracheal tubes supply O2 directly to body cells

• The respiratory and circulatory systems are separate

• Larger insects must ventilate their tracheal system to meet O2 demands


Tracheoles Mitochondria Muscle fiber

2.5

µm

Tracheae

Air sacs

External opening

Trachea

Airsac Tracheole

Bodycell

Air

Figure 42.24

Figure 42.24a

Tracheoles Mitochondria Muscle fiber

2.5

µm

Lungs

• Lungs are an infolding of the body surface• The circulatory system (open or closed) transports

gases between the lungs and the rest of the body• The size and complexity of lungs correlate with an

animal’s metabolic rate


Mammalian Respiratory Systems: A Closer Look

• A system of branching ducts conveys air to the lungs

• Air inhaled through the nostrils is warmed, humidified, and sampled for odors

• The pharynx directs air to the lungs and food to the stomach

• Swallowing tips the epiglottis over the glottis in the pharynx to prevent food from entering the trachea


Figure 42.25

Pharynx

Larynx(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm(Heart)

Capillaries

Leftlung

Dense capillary bedenveloping alveoli (SEM)

50 µm

Alveoli

Branch ofpulmonary artery(oxygen-poorblood)

Branch ofpulmonary vein(oxygen-richblood)

Terminalbronchiole

Nasalcavity

Pharynx

Larynx(Esophagus)

Trachea

Right lung

Bronchus

Bronchiole

Diaphragm

(Heart)

Leftlung

Nasalcavity

Figure 42.25a

Capillaries

Alveoli

Branch ofpulmonary artery(oxygen-poorblood)

Branch ofpulmonary vein(oxygen-richblood)

Terminalbronchiole

Figure 42.25b

Figure 42.25c

Dense capillary bedenveloping alveoli (SEM)

50 µm

• Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs

• Exhaled air passes over the vocal cords in the larynx to create sounds

• Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx

• This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the esophagus


• Gas exchange takes place in alveoli, air sacs at the tips of bronchioles

• Oxygen diffuses through the moist film of the epithelium and into capillaries

• Carbon dioxide diffuses from the capillaries across the epithelium and into the air space


• Alveoli lack cilia and are susceptible to contamination

• Secretions called surfactants coat the surface of the alveoli

• Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by artificial surfactants


RDS deaths Deaths from other causesRESULTS

40

30

20

10

00 800 1,600 2,400 3,200 4,000

Body mass of infant (g)

Su

rfac

e te

nsi

on

(d

ynes

/cm

)

Figure 42.26

Concept 42.6: Breathing ventilates the lungs

• The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air


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

• Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs

• Air passes through the lungs in one direction only• Every exhalation completely renews the air in the

lungs


Anteriorair sacs

Posteriorair sacs

Lungs

1 mm

Airflow

Air tubes(parabronchi)in lung

Anteriorair sacs

Lungs

Second inhalationFirst inhalation

Posteriorair sacs 3

2 4

1

4

31

2 Second exhalationFirst exhalation

Figure 42.27

Figure 42.27a

1 mm

Airflow

Air tubes(parabronchi)in lung

How a Mammal Breathes

• Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs

• Lung volume increases as the rib muscles and diaphragm contract

• The tidal volume is the volume of air inhaled with each breath


Figure 42.28

Rib cageexpands.

Airinhaled.

Airexhaled.

Rib cage getssmaller.

1 2

Lung

Diaphragm

• The maximum tidal volume is the vital capacity• After exhalation, a residual volume of air remains

in the lungs


Control of Breathing in Humans

• In humans, the main breathing control centers are in two regions of the brain, the medulla oblongata and the pons

• The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid

• The medulla adjusts breathing rate and depth to match metabolic demands

• The pons regulates the tempo


• Sensors in the aorta and carotid arteries monitor O2 and CO2 concentrations in the blood

• These sensors exert secondary control over breathing


Homeostasis:Blood pH of about 7.4

CO2 level

decreases. Stimulus:Rising level ofCO2 in tissues

lowers blood pH.Response:Rib musclesand diaphragmincrease rateand depth ofventilation.

Carotidarteries

AortaSensor/control center:Cerebrospinal fluid

Medullaoblongata

Figure 42.29

Concept 42.7: Adaptations for gas exchange include pigments that bind and transport gases

• The metabolic demands of many organisms require that the blood transport large quantities of O2 and CO2


Coordination of Circulation and Gas Exchange

• Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli

• In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air

• In tissue capillaries, partial pressure gradients favor diffusion of O2 into the interstitial fluids and CO2 into the blood


Exhaled air Inhaled air

Pulmonaryarteries

Systemicveins

Systemicarteries

Pulmonaryveins

Alveolarcapillaries

AlveolarspacesAlveolar

epithelialcells

Inhaledair

160

120

80

40

0Heart

8 1

2

3

46

7

CO2 O2

SystemiccapillariesCO2 O2

Body tissue5

(a) The path of respiratory gases in the circulatory system

(b) Partial pressure of O2 and CO2 at different points in the

circulatory system numbered in (a)

4321 5 6 7

Exhaledair

Pa

rtia

l p

res

su

re (

mm

Hg

)

PO2

PCO 2

8

Figure 42.30

Figure 42.30aExhaled air Inhaled air

Pulmonaryarteries

Systemicveins

Systemicarteries

Pulmonaryveins

Alveolarcapillaries

AlveolarspacesAlveolar

epithelialcells

Heart

SystemiccapillariesCO2 O2

Body tissue

(a) The path of respiratory gases in the circulatory system

CO2 O2

8 1

2

37

6 4

5

Inhaledair

160

(b) Partial pressure of O2 and CO2 at different points in the circulatory system numbered in (a)

1

Exhaledair

Pa

rtia

l pre

ssu

re (

mm

Hg

)PO 2

120

80

40

02 3 4 5 6 7 8

PCO 2

Figure 42.30b

Respiratory Pigments

• Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry

• Arthropods and many molluscs have hemocyanin with copper as the oxygen-binding component

• Most vertebrates and some invertebrates use hemoglobin

• In vertebrates, hemoglobin is contained within erythrocytes


Hemoglobin

• A single hemoglobin molecule can carry four molecules of O2, one molecule for each iron containing heme group

• The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2

• CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2; this is called the Bohr shift


Figure 42.UN01

Iron

Heme

Hemoglobin

Figure 42.31

2(a) PO and hemoglobin dissociation at pH 7.4

Tissues duringexercise

Tissuesat rest

Lungs

PO (mm Hg)2

(b) pH and hemoglobin dissociation

PO (mm Hg)2

0 20 40 60 80 1000

20

40

60

80

100

0 20 40 60 80 1000

20

40

60

80

100

Hemoglobinretains lessO2 at lower pH

(higher CO2

concentration)

pH 7.2pH 7.4

O2 unloaded

to tissuesduring exercise

O2

sa

tura

tio

n o

f h

em

og

lob

in (

%)

O2 unloaded

to tissuesat rest

O2

sa

tura

tio

n o

f h

em

og

lob

in (

%)

Figure 42.31a

2(a) PO and hemoglobin dissociation at pH 7.4

Tissues duringexercise

Tissuesat rest

Lungs

PO (mm Hg)2

0 20 40 60 80 1000

20

40

60

80

100

O2 unloaded

to tissuesduring exercise

O2 unloaded

to tissuesat rest

O2

sat

ura

tio

n o

f h

em

og

lob

in (

%)

(b) pH and hemoglobin dissociation

PO (mm Hg)2

0 20 40 60 80 1000

20

40

60

80

100

Hemoglobinretains lessO2 at lower pH

(higher CO2

concentration)

pH 7.2pH 7.4

O2 s

atu

rati

on

of

he

mo

glo

bin

(%

)

Figure 42.31b

Carbon Dioxide Transport

• Hemoglobin also helps transport CO2 and assists in buffering the blood

• CO2 from respiring cells diffuses into the blood and is transported either in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO3

–)


Animation: O2 from Lungs to Blood

Animation: CO2 from Blood to Lungs

Animation: CO2 from Tissues to Blood

Animation: O2 from Blood to Tissues


Animation: O2 from Blood to Tissues Right-click slide / select “Play”


Animation: CO2 from Tissues to Blood Right-click slide / select “Play”


Animation: CO2 from Blood to Lungs Right-click slide / select “Play”


Animation: O2 from Lungs to Blood Right-click slide / select “Play”

Figure 42.32 Body tissue

Capillarywall

Interstitialfluid

Plasmawithin capillary

CO2 transport

from tissuesCO2 produced

CO2

CO2

CO2

H2O

H2CO3 HbRedbloodcell Carbonic

acid

Hemoglobin (Hb)picks up

CO2 and H+.

H+HCO3−

Bicarbonate

+

HCO3−

HCO3−

To lungs

CO2 transport

to lungs

HCO3−

H2CO3

H2O

CO2

H++

HbHemoglobin

releasesCO2 and H+.

CO2

CO2

CO2

Alveolar space in lung

Figure 42.32aBody tissue

Capillarywall

Interstitialfluid

Plasmawithin capillary

CO2 transport

from tissuesCO2 produced

CO2

H2O

H2CO3 HbRedbloodcell Carbonic

acid

Hemoglobin (Hb)picks up

CO2 and H+.

H+HCO3−

Bicarbonate+

HCO3−

To lungs

CO2

CO2

Figure 42.32b

HCO3− CO2 transport

to lungs

H2CO3

H2O

H++

HbHemoglobin

releasesCO2 and H+.

CO2

Alveolar space in lung

To lungs

HCO3−

CO2

CO2

CO2

Respiratory Adaptations of Diving Mammals

• Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats

– For example, Weddell seals in Antarctica can remain underwater for 20 minutes to an hour

– For example, elephant seals can dive to 1,500 m and remain underwater for 2 hours

• These animals have a high blood to body volume ratio


• Deep-diving air breathers stockpile O2 and deplete it slowly

• Diving mammals can store oxygen in their muscles in myoglobin proteins

• Diving mammals also conserve oxygen by– Changing their buoyancy to glide passively

– Decreasing blood supply to muscles

– Deriving ATP in muscles from fermentation once oxygen is depleted


Figure 42.UN02

Exhaled air

Alveolarepithelialcells

Pulmonaryarteries

Systemicveins

Heart

CO2 O2

Body tissue

Systemiccapillaries

Systemicarteries

Pulmonaryveins

Alveolarcapillaries

Alveolarspaces

Inhaled air

CO2 O2

Figure 42.UN03

Fetus

Mother

PO (mm Hg)2

0 20 40 60 80 100

100

80

60

40

20

0

O2

satu

rati

on

of

hem

og

lob

in (

%)

Figure 42.UN04

Biology "B" / Ch42

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Transcript of Biology "B" / Ch42