4 - Circulation and Gas Exchange

8/18/2019 4 - Circulation and Gas Exchange

1/87

Circulation and Gas Exchange


2/87

Problem: How totransport O2 and nutrients

efectively in multicellularorganisms


3/87

• Every organism must exchangematerials with its environment

• Exchanges ultimately occur at thecellular level by crossing the plasmamembrane

ns: 1. The delivery of O2 and nutrientsneeded

2. Removal of CO2 and wastes


4/87

In unicellular organisms, theseexchanges occur directly with the

environment


5/87

• mall molecules can move between

cells andtheir surroundings by diusion

• !ifusion is only e"cient over smalldistances because the time it ta#es todifuse is proportional to the s$uare o%the distance

Tissue thickness

Rate of !iusion&nimals have developed cavities and

circulatory systems to transport gasses

and nutrients and to reduces the' (


6/87

The increase in animal

size through evolution

led to many steps in

delivering O2 and

nutrients to where theyare needed


7/87

Figure 42.1

Gills are an example of a specialized exchange

system in animals

O2 diffuses from the water into blood essels

!O2 diffuses from blood into the water


8/87

Figure 42.2b

(b) The planarian Dugesia, a flatworm

Mouth

Pharyn!astrovascular

cavity

" mm

)latworms have a gastrovascularcavity and a *at body that minimi+es

difusion distances

& "astrovascular cavity %unctions in both digestion

and distribution o% substances throughout the body


9/87

The #irculatory $ystem

-"ump # heart$s%

-Fluid # blood or

hemolymph

-&essels # interconnecting ascular

components

he Circulatory ystem

&ll circulatorysystems, -open orclosed. have/


10/87

Figure 42.'a

(a) %n open circulatory system

&eart

&emolymph in sinuses

Pores

Tubular heart

Hemolymph baths the organs directly

(b) % l d i l t t


11/87

(b) % closed circulatory system

'orsalvessel(main

heart)

%uiliaryhearts

$mall

branch vesselsin each organ

&eart

nterstitial fluid

lood

*entral vessels

blood is con0ned to vessels and is distinct %rom

the interstitial *uid


12/87

Organi+ation o% 1ertebrate

Circulatory ystems

• Humans and other vertebrates havea closed circulatory system calledthe cardiovascular system

• ypes o% blood vessels/ arteriesarterioles veins venules and ca#illaries

• lood *ow is one way in thesevessels3 &rteries and veins aredistinguished by the direction o%

blood *ow, not by O2 content


13/87

• $eins carry blood to theheart

• %rteries carry blood away

%rom the heart

&rteries and 1eins

Copyright 4 2567 8ohn 9iley : ons, Inc3 &ll rights reserved3


14/87

$ingle circulation+ fish

%rtery

&eart+%trium (%)

*entricle (*)

*ein

!illcapillaries

odycapillaries

ey Oygen-rich blood

Oygen-poor blood

; ony 0shes, rays, andshar#s have sin"lecirculation with a two&chambered heart

- In sin"le circulation,blood leaving the heartpasses through twocapillary beds be%ore

returning

- lood enters through anatrium and is pumpedout through a ventricle


15/87

$ystemic circuit

$ystemiccapillaries

%trium

(%)

.ungand s/incapillaries

%trium

(%)

0ight .eft

*entricle (*)

Pulmocutaneous circuit

ey Oygen-rich blood

Oygen-poor blood

(mphibians and reptiles)

)rogs and amphibians havea three&chambered

heart/ two atria and oneventricle

ouble circulation

Figure 42 4c


16/87

Figure 42.4c

ey Oygen-rich blood

Oygen-poor blood

'ouble circulation+mammal

Pulmonary circuit

.ungcapillaries

$ystemiccapillaries

$ystemic circuit

0ight .eft

% %

**

!ouble circulation maintainshigher blood pressure in theorgans than does singlecirculation

'ammals -and birds. alsohave a double circulation


17/87

Mammals and birds have a four-chambered

heart with two atria and two ventricles

*he left side of the heart pumps and receies onlyoxygen+rich blood) while the right side receies and

pumps only oxygen+poor blood


18/87


19/87

• lood begins its *ow with the ri"htventricle pumping blood to the lungsvia the #ulmonary arteries

• In the lungs, the blood loads O2 andunloads CO2

• Oxygen;rich blood %rom the lungsenters the heart at the left atriumvia the #ulmonary veins

he >ulmonary Circuit

Figure 42 ,


20/87

""

1Figure 42.,

$uperior

vena cava

Pulmonary

artery

#apillaries

of right lung

Pulmonary

vein

0ight atrium

0ight ventricle

nferior

vena cava

#apillaries of

abdominal organs

and hind limbs

%orta

%orta

.eft ventricle

.eft atrium

Pulmonary

vein

#apillaries

of left lung

Pulmonary

artery

#apillaries of

head and

forelimbs

3

4

5

2

6

"7

"8


21/87

• lood is pumped through the aorta to thebody tissues by the left ventricle

(strongest muscle of the heart)

• lood returns to the heart through the

su#erior vena cava -blood %rom head,

nec#, and %orelimbs. and inferior venacava -blood %rom trun# and hind limbs.

• he superior vena cava and in%erior venacava *ow into the ri"ht atrium

he ystemic Circuit


22/87

*he mammalian heart has a double circulation-

heart lungs heart systemic

*he two atria hae relatiely thin walls and sere as

collection chambers for blood returning to

the heart

*he entricles hae thicer walls $ left is the thicest%

and contract much more forcefully

n"s to Remember about a 'ammalian


23/87

he aorta provides blood to theheart through the coronary arteries


24/87

he heart is enclosed and held in placeby the pericardium

>ericardium



25/87

Pulmonaryartery

Pulmonary artery

0ight

atrium .eft

atrium

%orta

$emilunar

(pulmonary) valve

$emilunar (aortic)

*alve

%trioventricular

(%*) valve

(bicuspid or mitral)

%trioventricular

(%*) valve

(tricuspid)

0ight

ventricle

.eft

ventricle

$alves o#en and close to allowblood *ow between chambers


26/87

+i". ,&1, #.-

t $alves O#en and Close in Res#onse to Pres !ierences


27/87

1alves are One;way



28/87

-c. ricuspid valve open

C?> O) @IC?>I!1&A1E

CHO@!&E EB!IBE&E

>&>IAA&@


29/87

he heart contracts and relaxes in a rhythmic cyclecalled the cardiac cycle

• (ystole ; he contraction, or

pumping, phase• !iastole ; he relaxation, or 0lling,

phase

-In re%erence to ventricles.

DOne complete cycle o% pumping and 0lling

is called the Cardiac Cycle


30/87

%trial and

ventricular diastole"

79"

sec

796

sec

79 sec

%trial systole and

ventricular diastole

2

*entricular systole

and atrial diastole

/0ub /!ub

Aub onset o% systole-&1 valve closes.

!ub onset o% diastole

-&ortic valve closes.

he Cardiac Cycle

ne cardiac cycle 3.4 sec.

h bl d th h th h


31/87

• heart rate, ;the number o% beats per minute/

2 beats5min• stroke volume& the amount o% blood

pumped in a single contraction/

3 m0

• cardiac out#ut ; the volume o% bloodpumped into the systemic circulation #erminute

6 05min 2 beats5min 7 3 m05beat

ow much blood moves through the hea

iac out#ut heart rate 7 stroke v


32/87

9hat determines Cardiac OutputFCO-mAmin.

• Stroke Volume and HeartRate

-

9hen the heart beats %aster,more blood is pumped into thecirculation per minute

; 9hen the heart musclescontract harder, more blood is

emptied into system


33/87

Cardiac muscle cells are sel%;excitable,and there%ore, autorhythmic

# Cardiac muscle cells repeatedlygenerate spontaneous action potentialsthat then trigger heart contractions

he Conduction ystem



34/87


35/87

%ction potentials

travels through

gap :unctions

%tria and ventricles

have separate

conductive muscles

- no gap :unctions

between them

< i t i i th H t @h th i


36/87

$ignals (yellow)from $% nodespread throughatria9

$% node(pacema/er)

;#!

he sinoatrial 8(%9

node, or pacema#er,sets the rate and timingat which cardiac musclecells contract


37/87


" $ignals aredelayed at %*node9

%*node

$% node(pacema/er)

;#!

Impulses %rom the & node travel to theatrioventricular 8%$9 node wherethey are delayed


38/87



2 undle branchespass signals toheart ape9

&eartape

undlebranches

%*node$% node

(pacema/er)

;#!

Bext, the impulses travel through thebundle branches -undle o% His. to the

heart apex, whereJ


39/87



2 undle branchespass signals toheart ape9

$ignalsspreadthroughoutventricles9

6

Pur/in:efibers&eart

ape

undlebranches

%*node$% node

(pacema/er)

;#!

J they travel to the Purkine ;bers whicma#e the ventricles contract3


40/87

The


41/87

• he sym#athetic division speeds

up the pacema#er = norepinephrineand epinephrine

• he #arasym#athetic divisionslows down the pacema#er ;acetylcholine

Bervous system regulation

o% the pacema#er

1 l i h i l


42/87

1essels in the circulatorysystem

1eins

&rteries

venules

Capillaries

&rterioles

ac# to the heart

&rteries have thic#er walls than veins to


43/87

%rtery *ein

0ed blood cells

&rteries have thic#er walls than veins toaccommodate the high pressure o% blood

pumped %rom the heart

Figure 42.c


44/87

0ed blood cell

#apillary

Capillaries have thin walls, the endothelium plus itsbasal lamina, to %acilitate the exchange o% materials

Capillaries are only slightly wider than ared

blood cell

he epithelial layer that lines blood vessels is


45/87

asal lamina

;ndothelium

$moothmuscle

#onnectivetissue

*ein

#onnectivetissue

$moothmuscle

;ndothelium

#apillary

%rtery

%rteriole*enule

*alve

he epithelial layer that lines blood vessels iscalled the endothelium. It is smooth and

minimi+es resistance3

1elocity o% blood is lower in veins than in


46/87

'irection of blood flowin vein (toward heart)

*alve (open)

$/eletal muscle

*alve (closed)

1elocity o% blood is lower in veins than inarteries3 o, why does blood continue to

*ow towards heartF

One;way valvesprevent bac#*ow

#eletal muscle

contraction alsomoves blood along


47/87

lood )low 1elocity

• peed in which blood *ows isinversely #ro#ortional the totalcross;sectional area o% the vessels

• Ca#illaries have the hi"hest cumulative cross;sectional area,

there%ore blood moves slowestthrough the capillaries3

8 777 Collectively


48/87

$ystolicpressure

'iastolicpressure

% o r t a

% r t e r i e s

% r t e r i o

l e s

#

a p

i l l a r i e s

* e n u

l e s

* e

i n s

* e n a e

c a v a e

P r e s s u r e

( m

m &

g )

"27"77

5747

67277

* e

l o c

i t y

( c m

ressure isgreatest inthe &orta

Collectively,capillarieshave thegreatest area

he thecross;sectional

area, thethe velocity o%blood

&elocity of blood flow is slowest in the capillary


49/87

&elocity of blood flow is slowest in the capillary

beds) as a result of the high resistance and large

total cross+sectional area

3lood flow in capillaries is necessarily slow for

exchange of materials


50/87

• wo mechanisms regulatedistribution o% blood in capillary beds

# Constriction or dilation of arteriolesthat supplycapillary beds -regulated by nerveimpulses , hormones, or other

chemicals. # Preca#illary s#hincters that control*ow o% bloodbetween arterioles and venules

Ca#illary +unction

Figure 42.1'Precapillary sphincters Thoroughfare


51/87

channel

%rteriole

#apillaries

*enule

(a) $phincters relaed

%rteriole *enule

(b) $phincters contracted


52/87

8a9

do e acell

Pores

Ca#illary

;ndothelial cells of capillaries fit together li/e a

:igsaw puzzle

%llows passage

of water soluble

substances

.ipid soluble substances

do not need the pores,

but pass through the cells

directly

The e7chan"e of substances across


53/87

%rterial end

of capillary 'irection of blood flow*enous end

of capillary

Osmotic

pressure

lood

pressure

=et fluid movement out=T;0$TT%.>.?' ody cell

"ca#illary walls.

-

@egulated by blood pressure and osmoticpressure-lood proteins rarely pass through endotheliumand help maintain osmotic pressure

lood


54/87

+i". ,&- #.-?1

Plasma 66@ of whole blood

Packed cellvolume orhematocrit

Red blood cells A6@ of whole blood

Bhite blood cells

/uy coatD1@

Platelets

@ hematocrit varies with species and with

stress levels9

loodComposition and

)unction


55/87

What is Plasma?

• >lasma contains inorganic salts, sometimescalled electrolytes

• Plasma #roteins in*uence blood pH andhelp maintain osmotic balance between

blood and interstitial *uid• >articular plasma proteins %unction in lipid

transport, immunity, and blood clotting

• >lasma is similar in composition tointerstitial*uid, but plasma has a much higher proteinconcentration


56/87

Cellular Elements of Blood

• uspended in blood plasma are two typeso% cells

# Red blood cells -erythrocytes. transport O23

he hormone erythro#oietin 8


57/87

>l i t t t C ll i i t


58/87

>luripotent tem Cells give rise toAymphoid and


59/87

;rythrocytes

• @ed blood cells, or erythrocytes, are themost numerous blood cells

• hey contain hemo"lobin, the iron;containing protein that transports O2

• Each molecule o% hemoglobin binds up to

%our molecules o% O2• In mammals, mature erythrocytes

lac# nuclei and mitochondria

&emoglobin

&eme

ron

*One erythrocyte contains ~250 billion hemoglobinmolecules


60/87

KLm

ur%ace view

ectioned view

-a. @C shape

@ed lood Cells

Have no nucleus ormembrane boundorganelles

How would the

biconcave shape o% thecells bene0t difusion o%O2F

RCE( 8


61/87

• ac intracellular organelles necessary for cellular repair) growth) diision

• $hort .ife $pan $5126 days%

• 0uptured 0#As are destroyed in spleen) lier or bone marrow

–

"hagocytic 73!8s 9clear the debris:

RCE( 8


62/87

Res#iration• =as e7chan"e supplies O2 %or cellular

respiration and disposes o% CO2

• Gas exchange occurs across speciali+edrespiratory sur%aces

$ til ti th i t


63/87

(a) Marine worm

Parapodium

(functions as gill)

(b) #rayfish

!ills

(c) $ea star

Tube foot

!ills

#oelom

$entilation moves the respiratorymedium over the respiratory sur%ace

Figure 42.22a


64/87

!ill filaments

!ill arch

loodvessels

!ill

arch

Bater

flow

Operculum

In 0sh gills, more than

K5M o% the O2 dissolved in the wateris removed as waterpasses over the

Figure 42.2'Tracheoles Mitochondria Muscle fiber


65/87

2 9 8

C m

Tracheae

%ir sacs

;ternal opening (spiracles)

Trachea

%ir

%ir

sac Tracheole

ody

cell

oo# lungs o%


66/87

oo# lungs o%the pider

ammalian @espiratory ystem


67/87

.eft lung

=asal

cavity

(&eart)

Pharyn

.aryn

(;sophagus)

Trachea

0ight lung

ronchus

ronchiole

'iaphragm

ammalian @espiratory ystem

.ungs are encased in a membraneous

pleural sac


68/87

+i". 11&1A #.A

8a9

Bater&;lledballoon

!ia#hra"m

Thoracic wall

i"ht #leural sac

0eft

lun"

Ri"ht

lun"

Pleural cavity ;lledwith intra#leural *uid

$isceral #leura

Parietal #leura

0eft #leural sac

/0un"

/Pleural sac

8b9

0olli#o#

pleural sac

that is filled

with fluid

between its cavity

he right lung has three lobes, the


69/87

-b. Aateral view o% rightlung

&pex

uperior lobe

&BE@IO@

OE@IO@

-c. Aateral view o% le%tlung

Obli$ue 0ssur

In%erior lobe

>OE@IO@

he right lung has three lobes, thele%t lung has two lobes

Trachea


70/87

(&eart)

ronchus

ronchiole

'iaphragm

&natomy o% &lveoli


71/87

%lveoli

#apillaries

Terminal

bronchiole

ranch of

pulmonary vein(oygen-rich

blood)

ranch of

pulmonary artery

(oygen-poor

blood)

255 = N55 million alveoli in a human lung

y

e7chan"e occurs in the alveoli

• &lveoli lac# cilia and are susceptible


72/87

• &lveoli lac# cilia and are susceptible

to contamination

• ecretions called surfactants coatthe sur%ace o% the alveoli

• >reterm babies lac# sur%actant and

are vulnerable to respiratory distresssyndrome treatment is provided byarti0cial sur%actants

ow much air can the lun"s holdF


73/87

• he the volume o% air inhaled witheach breath ; P Q55ml -idal 1olume.

• )orced inhalationexhalation P 7 A-1ital capacity.

• here is always air le%t behind in thelungs P632A -residual volume.

ow much air can the lun"s holdF

Q = R A


74/87

2 ;D&%.%TO=+ 'iaphragmrelaes (moves up)9

" =&%.%TO=+ 'iaphragmcontracts (moves down)9

'iaphragm

.ung

0ib cageepands asrib musclescontract9

0ib cagegets smaller

as rib musclesrela9

Aung volume increases as the rib muscles

and dia#hra"m contract

#ressure breathin", which pulls air into thelungs

>artial >ressure Gradients in Gas


75/87

>artial >ressure Gradients in Gas

Exchange

• Partial #ressure is the pressureexerted by a particular gas in amixture o% gases

• Gases undergo net difusion %rom aregion o% higher partial pressure to aregion o% lowerpartial pressure

Bhen the chest e7#ands the volume


76/87

of the lun"s increases. The #ressuree7erted by o7y"en within the lun"s

decreases therefore o7y"en diusesinto the lun"s

Ri"ht #leural sac

!ia#hra"m

O2>52 6R5 mmHg

>52 S 6R5 mmHg

Figure 42.2

"27"47


77/87

"

Pulmonary

veins and

systemic

arteries

2

8

4

6

$ystemic

capillaries

%lveolar

capillaries

%lveolar spaces

nhaled air

O2#O2

#O2 O2ody

tissue

Pulmonary

arteries

and systemic

veins

lood

entering

alveolar

capillaries

%lveolar

epithelial

cells

;haled air 21

P#O 2PO 2

67 68

P#O 2PO 2

P#O 2PO 2

E67F68

792

P#O 2PO 2

"76

67

P#O 2PO 2

"76

67

P#O 2PO 2

i i


78/87

@espiratory >igments

• Res#iratory #i"ments, proteins thattransport oxygen, greatly increase theamount o% oxygen that blood can

carry• &rthropods and many molluscs have

hemocyanin with copper as the

oxygen;binding component• In vertebrates, hemoglobin is

contained within erythrocytes

Poly#e#tide chain&emoglobin (&b)


79/87

y# #

Gronatomwithinheme"rou#

Poly#e#tide chain

Poly#e#tide chai)eme "rou#s

&emoglobin (&b)

$tructure+•>our polypeptide

chains•>our iron-containing

heme groups

;ach hemoglobin

molecule binds to

four O2 molecules

P P T P P P


80/87

OO

O

O

O

OO

OOO

O

OO

O

O

O

O

OO

OO

O

O

O

O

O

OO

O

OO

O

OO

O

O

O O2 Hb

PO2

PO2

PO2 T PO2 PO2 PO2

Only unbound O2 contributes to PO2 Figure 42.'6a

O l d d"77

@ )


81/87

O2 unloaded

to tissues

at rest

O2 unloadedto tissues

during

eercise

57

47

67

27

7"77574767277

O 2

s a t u

r a t i o n o f h e m o

g l o b i n ( @

Tissues during

eercise

Tissues

at rest

.ungs

PO (mm &g)2

(a) PO and hemoglobin dissociation at p& 1962

ohr (hift


82/87

(b) p& and hemoglobin dissociation

p& 196

p& 192

&emoglobin

retains less

O2 at lower p&(higher #O2concentration)

"77

57

47

67

27

7"77574767277

O

2 s a t u r a t i o n o f h e m o g l o b i n ( @ )

PO (mm &g)2

ohr (hift

C b i id " t


83/87

Carbon io!ide "rans#ort

• ome CO2 %rom respiring cells difuses intothe blood and is transported in bloodplasma, bound to hemoglobin

• he remainder difuses into erythrocytesand reacts with water to %orm H2CON, which

dissociates into HU and bicarbonate ions-HCONV.

• In the lungs the relative partial pressures o%CO2 %avor the net difusion o% CO2 out o% the

blood

Control o% reathing in


84/87

Control o% reathing inHumans

• In humans, breathing is usuallyregulated by involuntary mechanisms

• he breathing control centers are %oundin the medulla oblongata o% the brain

• he medulla regulates the rate anddepth o% breathing in response to pHchanges in the cerebrospinal *uid

Figure 42.2;


85/87

=O0M%. .OO' p&

(about 196)

lood #O2 level falls

and p& rises9 lood p& fallsdue to rising levels of

#O2 in tissues (such as

when eercising)9Medulla detects

decrease in p& of

cerebrospinal fluid9

#erebrospinal

fluid #arotid

arteries

%orta

Medulla

oblongata Medulla receives

signals from ma:or

blood vessels9

$ensors in ma:or blood vessels

detect decreasein blood p&9

$ignals frommedulla to ribmuscles anddiaphragmincrease rateand depth of ventilation9


86/87

• ensors in the aorta and carotid arteries

monitor O2 and CO2 concentrations in the

blood

• hese signal the breathing control centers,

which respond as needed• &dditional modulation o% breathing ta#es

place in the pons, next to the medulla

CO2 is the main determinant o% pH in


87/87

CO2 is the main determinant o% pH in

the blood

How is pH regulatedF

4 - Circulation and Gas Exchange

Documents

Transcript of 4 - Circulation and Gas Exchange