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Apago PDF Enhancer
I
Ch
ap
ter 50
The
Cir
cula
tory
Sys
tem
Ch
ap
ter
Ou
tlin
e
50
.1
Th
e C
om
po
nen
ts o
f B
loo
d
50
.2
Inve
rteb
rate
Cir
cula
tory
Sys
tem
s
50
.3
Ver
teb
rate
Cir
cula
tory
Sys
tem
s
50
.4
Th
e F
ou
r-C
ham
ber
ed H
eart
an
d t
he
Blo
od
Ves
sels
50
.5
Ch
arac
teri
stic
s o
f B
loo
d V
esse
ls
50
.6
Reg
ula
tio
n o
f B
loo
d F
low
an
d B
loo
d P
ress
ure
Intr
od
uc
tio
n
In m
ult
ice
llu
lar
org
an
ism
s, o
xyg
en o
bta
ined
by
the
resp
ira
tory
sys
tem
an
d n
utr
ien
ts p
roce
ssed
by
the
dig
esti
ve s
yste
m m
ust
be
tra
nsp
ort
ed t
o c
ells
th
rou
gh
ou
t th
e b
od
y. C
on
vers
ely,
ca
rbo
n d
ioxi
de
an
d o
ther
wa
ste
pro
du
cts
pro
du
ced
wit
hin
th
e ce
lls m
ust
be
retu
rned
to
th
e re
spir
ato
ry, d
iges
tive
, an
d u
rin
ary
sys
tem
s fo
r el
imin
ati
on
fro
m t
he
bo
dy.
Th
ese
task
s a
re t
he
resp
on
sib
ility
of t
he
circ
ula
tory
sys
tem
. All
mu
ltic
ellu
lar
org
an
ism
s h
ave
a h
eart
th
at
pu
mp
s !
uid
s th
rou
gh
th
e b
od
y. M
an
y in
vert
ebra
tes
ha
ve a
n o
pen
syst
em in
wh
ich
! u
ids
mo
ve t
hro
ug
h t
he
bo
dy
cavi
ty. V
erte
bra
tes
als
o h
ave
a s
yste
m li
ke t
his
th
at
mo
ves
lym
ph
th
rou
gh
the
bo
dy;
ho
wev
er, t
he
pri
ma
ry c
ircu
lato
ry !
uid
is b
loo
d, w
hic
h m
ean
s th
rou
gh
a c
lose
d s
yste
m o
f blo
od
ves
sels
.
pla
tele
ts,
alth
ou
gh
in
clu
ded
in
fig
ure
50
.1,
are
no
t co
mp
lete
ce
lls;
rat
her
, th
ey a
re f
rag
men
ts o
f ce
lls
that
are
pro
du
ced
in t
he
bo
ne
mar
row
. (W
e d
escr
ibe
the
acti
on
of
pla
tele
ts i
n b
loo
d
clo
ttin
g l
ater
in
th
is s
ecti
on
.)
Cir
cula
tin
g b
loo
d h
as m
any
fun
ctio
ns:
Tra
nsp
ort
atio
n.
1.
All
of
the
sub
stan
ces
esse
nti
al f
or
cell
ula
r m
etab
oli
sm a
re t
ran
spo
rted
by
blo
od
. Red
blo
od
ce
lls
tran
spo
rt o
xyg
en a
ttac
hed
to
hem
og
lob
in;
nu
trie
nt
mo
lecu
les
are
carr
ied
in
th
e p
lasm
a, s
om
etim
es b
ou
nd
to
ca
rrie
rs;
and
met
abo
lic
was
tes
are
elim
inat
ed a
s b
loo
d
pas
ses
thro
ug
h t
he
live
r an
d k
idn
eys.
Reg
ula
tio
n.
2.
Th
e ca
rdio
vasc
ula
r sy
stem
tra
nsp
ort
s re
gu
lato
ry h
orm
on
es f
rom
th
e en
do
crin
e g
lan
ds
and
als
o
5
0.1
Th
e C
om
po
nen
ts o
f Blo
od
Le
arn
ing
Ou
tco
me
s
De
scri
be
the
fun
ctio
ns
of
circ
ula
tin
g b
loo
d.
1.
Dis
tin
gu
ish
be
twe
en
th
e ty
pe
s o
f fo
rme
d e
lem
en
ts.
2.
De
lin
ea
te t
he
pro
cess
of
blo
od
clo
ttin
g.
3.
Blo
od
is
a co
nn
ecti
ve t
issu
e co
mp
ose
d o
f a
flu
id m
atri
x, c
alle
d
pla
sma,
an
d s
ever
al d
iffe
ren
t ki
nd
s o
f ce
lls
and
oth
er f
orm
ed
ele
men
ts t
hat
cir
cula
te w
ith
in t
hat
flu
id (
fig
ure
50
.1) .
Blo
od
CH
AP
TE
R
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M % N %
L
! % M % %
! O ! % M % % K
K #
M % N %
Fig
ure
50
.2
Ste
m c
ell
s a
nd
th
e p
rod
uc
tio
n o
f fo
rme
d e
lem
en
ts.
10
20
p
art
VII
An
ima
l Fo
rm a
nd
Fu
nct
ion
Apago PDF Enhancer P QN % /
R QS # T% # # /
U QV # W /
X QY Z ## % % # /[ Q #% # /
N N #
Pla
tele
ts
Pla
tele
ts a
re c
ell
frag
men
ts t
hat
pin
ch o
ff f
rom
lar
ger
cel
ls i
n
the
bo
ne
mar
row
. T
hey
are
ap
pro
xim
atel
y 3
m
in
dia
met
er,
and
fo
llo
win
g a
n i
nju
ry t
o a
blo
od
ves
sel,
the
live
r re
leas
es p
ro-
thro
mbi
n i
nto
th
e b
loo
d. I
n t
he
pre
sen
ce o
f th
is c
lott
ing
fac
tor,
fi
bri
no
gen
is
con
vert
ed i
nto
in
solu
ble
th
read
s o
f fi
bri
n.
Fib
rin
th
en a
gg
reg
ates
to
fo
rm t
he
clo
t.
Fo
rme
d e
lem
en
ts a
rise
fro
m s
tem
ce
lls
Th
e fo
rmed
ele
men
ts o
f b
loo
d e
ach
hav
e a
fin
ite
life
sp
an a
nd
th
eref
ore
mu
st b
e co
nst
antl
y re
pla
ced
. M
any
of
the
old
cel
l fr
agm
ents
are
dig
este
d b
y p
hag
ocy
tic
cell
s o
f th
e sp
leen
; h
ow
-ev
er, m
any
pro
du
cts
fro
m t
he
old
cel
ls, s
uch
as
iro
n a
nd
am
ino
ac
ids,
are
in
corp
ora
ted
in
to n
ew f
orm
ed e
lem
ents
. T
he
cre-
atio
n o
f n
ew f
orm
ed e
lem
ents
beg
ins
in t
he
bo
ne
mar
row
(se
e ch
apte
r 4
7).
A
ll o
f th
e fo
rmed
ele
men
ts d
evel
op
fro
m p
luri
po
ten
t st
em
cell
s (s
ee c
hap
ter
19
). T
he
pro
du
ctio
n o
f b
loo
d c
ells
oc-
curs
in
th
e b
on
e m
arro
w a
nd
is
call
ed h
em
ato
po
iesi
s. T
his
p
roce
ss g
ener
ates
tw
o t
ypes
of
stem
cel
ls w
ith
a m
ore
res
tric
ted
fa
te:
a ly
mp
ho
id s
tem
cel
l th
at g
ives
ris
e to
lym
ph
ocy
tes
and
a
mye
loid
ste
m c
ell
that
giv
es r
ise
to t
he
rest
of
the
blo
od
cel
ls
(fig
ure
50
.2) .
W
hen
th
e o
xyg
en a
vail
able
in
th
e b
loo
d d
ecre
ases
, th
e ki
dn
ey c
on
vert
s a
pla
sma
pro
tein
in
to t
he
ho
rmo
ne
ery
thro
-p
oie
tin
. E
ryth
rop
oie
tin
th
en
stim
ula
tes
the
pro
du
ctio
n
of
eryt
hro
cyte
s fr
om
th
e m
yelo
id s
tem
cel
ls t
hro
ug
h a
pro
cess
ca
lled
ery
thro
po
iesi
s .
In m
amm
als,
mat
uri
ng
eryt
hro
cyte
s lo
se t
hei
r n
ucl
ei p
rio
r to
rel
ease
in
to c
ircu
lati
on
. In
co
ntr
ast,
th
e m
atu
re e
ryth
rocy
tes
of
all o
ther
ver
teb
rate
s re
mai
n n
ucl
eate
d. M
egak
aryo
cyte
s are
ex-
amp
les
of
com
mit
ted
cel
ls f
orm
ed i
n b
on
e m
arro
w f
rom
ste
m
cell
s. P
iece
s o
f cy
top
lasm
are
pin
ched
off
th
e m
egak
aryo
cyte
s to
fo
rm t
he
pla
tele
ts.
Inq
uir
y q
ue
stio
n
?
Wh
y d
o y
ou
th
ink
th
e u
se o
f e
ryth
rop
oie
tin
as
a d
rug
is
ba
nn
ed
in t
he
Oly
mp
ics
an
d in
so
me
oth
er
spo
rts?
Blo
od
clo
ttin
g is
an
ex
am
ple
of
an
en
zym
e c
asc
ad
e
Wh
en a
blo
od
ves
sel i
s b
roke
n o
r cu
t, s
mo
oth
mu
scle
in t
he
ves-
sel
wal
ls c
on
trac
ts, c
ausi
ng t
he
vess
el t
o c
on
stri
ct. P
late
lets
th
en
accu
mu
late
at
the
inju
red
sit
e an
d f
orm
a p
lug b
y st
icki
ng t
o o
ne
ano
ther
an
d t
o t
he
surr
ou
nd
ing t
issu
es (
figu
re 5
0.3
) . A
cas
cad
e o
f en
zym
atic
rea
ctio
ns
is t
rigger
ed b
y th
e p
late
lets
, pla
sma
fac-
tors
, an
d m
ole
cule
s re
leas
ed f
rom
th
e d
amag
ed t
issu
e.
On
e o
f th
e re
sult
s o
f th
is c
asca
de
is t
hat
fib
rin
og
en, n
or-
mal
ly d
isso
lved
in
th
e p
lasm
a, c
om
es o
ut
of
solu
tio
n i
n a
rea
c-ti
on
th
at f
orm
s fi
bri
n. T
he
pla
tele
t p
lug
is
then
rei
nfo
rced
by
fib
rin
th
read
s, w
hic
h c
on
trac
t to
fo
rm a
tig
hte
r m
ass.
Th
e ti
gh
t-en
ing
plu
g o
f p
late
lets
, fi
bri
n,
and
oft
en t
rap
ped
ery
thro
cyte
s co
nst
itu
tes
a b
loo
d c
lot.
O
nce
th
e ti
ssu
e d
amag
e is
hea
led
, th
e ca
refu
l p
roce
ss o
f d
isso
lvin
g t
he
blo
t cl
ot
beg
ins.
Th
is p
roce
ss i
s si
gn
ific
ant
be-
cau
se i
f a
clo
t b
reak
s lo
ose
an
d t
rave
ls i
n t
he
circ
ula
tory
sys
-te
m, i
t m
ay e
nd
up
blo
ckin
g a
blo
od
ves
sel i
n t
he
bra
in, c
ausi
ng
a
stro
ke, o
r in
th
e h
eart
, cau
sin
g a
hea
rt a
ttac
k.
Le
arn
ing
Ou
tco
me
s R
ev
iew
50
.1Th
e ci
rcul
ator
y sy
stem
func
tion
s in
tran
spor
t of m
ater
ials
, reg
ulat
ion
of
tem
pera
ture
and
bod
y pr
oces
ses,
and
pro
tect
ion
of th
e bo
dy. F
orm
ed
elem
ents
in b
lood
incl
ude
red
bloo
d ce
lls, w
hite
blo
od c
ells
, and
pla
tele
ts.
Blo
od c
lott
ing
invo
lves
a c
asca
de o
f enz
ymat
ic re
acti
ons
trig
gere
d by
plat
elet
s an
d pl
asm
a fa
ctor
s to
pro
duce
inso
lubl
e fi
brin
from
fi br
inog
en.
H
ow
do
es
a b
loo
d c
lot
form
?
Fig
ure
50
.3 B
loo
d c
lott
ing
. F
ibri
n i
s fo
rmed
fro
m a
so
lub
le p
rote
in,
! b
rin
og
en,
in t
he
pla
sma.
Th
is r
eact
ion
is
cata
lyze
d b
y th
e
enzy
me
thro
mb
in,
wh
ich
is
form
ed f
rom
an
in
acti
ve e
nzy
me
call
ed p
roth
rom
bin
. T
he
acti
vati
on
of
thro
mb
in i
s th
e la
st s
tep
in
a c
asca
de
of
enzy
mat
ic r
eact
ion
s th
at p
rod
uce
s a
blo
od
clo
t w
hen
a b
loo
d v
esse
l is
dam
aged
.
cha
pte
r 5
0
Th
e C
ircu
lato
ry S
yste
m
10
21
ww
w.r
av
en
bio
log
y.c
om
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c.D ,;5 *H.- 1' ,*GJ G+' )3` *1++( ,44)*& 4)6;5 *H.- 1'5 ,6
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a % M W a
a L F
igu
re 5
0.4
Cir
cula
tory
sy
ste
ms
of
the
an
ima
l k
ing
do
m.
a.
Sp
on
ges
(le
ft p
anel
) d
o n
ot
hav
e a
sep
arat
e ci
rcu
lato
ry s
yste
m.
Th
ey
circ
ula
te w
ater
usi
ng
man
y in
curr
ent
po
res
and
on
e ex
curr
ent
po
re.
Th
e g
astr
ova
scu
lar
cavi
ty o
f a
hyd
ra (
mid
dle
pan
el )
serv
es a
s b
oth
a
dig
esti
ve a
nd
a c
ircu
lato
ry s
yste
m,
del
iver
ing
nu
trie
nts
dir
ectl
y to
th
e ti
ssu
e ce
lls
by
dif
fusi
on
fro
m t
he
dig
esti
ve c
avit
y. T
he
nem
ato
de
(rig
ht
pan
el )
is t
hin
en
ou
gh
th
at t
he
dig
esti
ve t
ract
can
als
o b
e u
sed
as
a ci
rcu
lato
ry s
yste
m.
Lar
ger
an
imal
s re
qu
ire
a se
par
ate
circ
ula
tory
sys
tem
to
carr
y n
utr
ien
ts t
o a
nd
was
tes
away
fro
m t
issu
es. b.
In t
he
op
en c
ircu
lati
on
of
an i
nse
ct, h
emo
lym
ph
is
pu
mp
ed f
rom
a t
ub
ula
r h
eart
in
to
cavi
ties
in
th
e in
sect
s b
od
y; t
he
hem
oly
mp
h t
hen
ret
urn
s to
th
e b
loo
d v
esse
ls s
o t
hat
it
can
be
reci
rcu
late
d. c.
In
th
e cl
ose
d c
ircu
lati
on
of
the
eart
hw
orm
, b
loo
d p
um
ped
fro
m t
he
hea
rts
rem
ain
s w
ith
in a
sys
tem
of
vess
els
that
ret
urn
s it
to
th
e h
eart
s. A
ll v
erte
bra
tes
also
hav
e cl
ose
d
circ
ula
tory
sys
tem
s.
5
0.2
In
vert
ebra
te C
ircu
lato
ry
Syst
ems
Le
arn
ing
Ou
tco
me
s
Dis
tin
gu
ish
be
twe
en
op
en
an
d c
lose
d c
ircu
lato
ry s
yste
ms.
1.
De
fin
e h
em
oly
mp
h.
2.
Th
e n
atu
re o
f th
e ci
rcu
lato
ry s
yste
m i
n m
ult
icel
lula
r in
vert
e-b
rate
s is
dir
ectl
y re
late
d t
o t
he
size
, co
mp
lexi
ty, a
nd
lif
esty
le o
f th
e o
rgan
ism
in
qu
esti
on
. Sp
on
ges
an
d m
ost
cn
idar
ian
s u
tili
ze
wat
er f
rom
th
e en
viro
nm
ent
as a
cir
cula
tory
flu
id.
Sp
on
ges
p
ass
wat
er t
hro
ug
h a
ser
ies
of
chan
nel
s in
th
eir
bo
die
s, a
nd
H
ydra
an
d
oth
er
cnid
aria
ns
circ
ula
te
wat
er
thro
ug
h
a g
astr
ova
scu
lar
cavi
ty (
fig
ure
50
.4a)
. Bec
ause
th
e b
od
y w
all
in
Hyd
ra s
pec
ies
is o
nly
tw
o c
ell
laye
rs t
hic
k, e
ach
cel
l la
yer
is i
n
dir
ect
con
tact
wit
h e
ith
er t
he
exte
rnal
en
viro
nm
ent
or
the
gas
-tr
ova
scu
lar
cavi
ty.
P
seu
do
coel
om
ate
inve
rteb
rate
s (r
ou
nd
wo
rms,
ro
tife
rs)
use
th
e fl
uid
s o
f th
e b
od
y ca
vity
fo
r ci
rcu
lati
on
. Mo
st o
f th
ese
inve
rteb
rate
s ar
e q
uit
e sm
all
or
are
lon
g a
nd
th
in,
and
th
ere-
fore
ad
equ
ate
circ
ula
tio
n is
acc
om
pli
shed
by
mo
vem
ents
of
the
bo
dy
agai
nst
th
e b
od
y fl
uid
s, w
hic
h a
re i
n d
irec
t co
nta
ct w
ith
th
e in
tern
al t
issu
es a
nd
org
ans.
Lar
ger
an
imal
s, h
ow
ever
, hav
e ti
ssu
es t
hat
are
sev
eral
cel
l la
yers
th
ick,
so
th
at m
any
cell
s ar
e
10
22
p
art
VII
An
ima
l Fo
rm a
nd
Fu
nct
ion
Apago PDF Enhancer
Systemic
capillaries
Respiratory
capillaries
Gills
Sinus
venosus
Ventricle
Conus
arteriosus
Atrium
Body
5
0.3
V
erte
bra
te C
ircu
lato
ry S
yste
ms
Le
arn
ing
Ou
tco
me
s
Tra
ce t
he
evo
luti
on
of
the
cha
mb
ere
d h
ea
rt f
rom
1.
la
nce
lets
to
bir
ds
an
d m
am
ma
ls.
De
lin
ea
te t
he
flo
w o
f b
loo
d t
hro
ug
h t
he
circ
ula
tory
2
. sy
ste
m in
bir
ds
an
d m
am
ma
ls.
Fig
ure
50
.5 T
he
he
art
an
d c
ircu
lati
on
of
a #
sh
. D
iag
ram
of
a !
sh h
eart
, sh
ow
ing t
he
stru
ctu
res
in s
erie
s w
ith
eac
h o
ther
(sin
us
ven
osu
s; a
triu
m; ve
ntr
icle
s; c
on
us
arte
rio
sus)
th
at f
orm
tw
o
pu
mp
ing
ch
amb
ers.
Blo
od
is
pu
mp
ed b
y th
e ve
ntr
icle
th
rou
gh
th
e
gil
ls a
nd
th
en t
o t
he
bo
dy.
Blo
od
ric
h i
n o
xyg
en (
oxy
gen
ated
) is
sho
wn
in
red
; b
loo
d l
ow
in
oxy
gen
(d
eoxy
gen
ated
) is
sh
ow
n i
n b
lue.
too
far
aw
ay f
rom
th
e b
od
y su
rfac
e o
r d
iges
tive
cav
ity
to d
i-re
ctly
exc
han
ge
mat
eria
ls w
ith
th
e en
viro
nm
ent.
In
stea
d, o
xy-
gen
an
d n
utr
ien
ts a
re t
ran
spo
rted
fro
m t
he
envi
ron
men
t an
d
dig
esti
ve c
avit
y to
th
e b
od
y ce
lls
by
an i
nte
rnal
flu
id w
ith
in a
ci
rcu
lato
ry s
yste
m.
Op
en
cir
cula
tory
sy
ste
ms
mo
ve
" u
ids
in a
on
e-w
ay
pa
th
Th
e tw
o m
ain
typ
es o
f ci
rcu
lato
ry s
yste
ms
are
open
an
d c
lose
d.
In a
n o
pen
cir
cula
tory
sys
tem
, su
ch a
s th
at f
ou
nd
in
mo
st m
ol-
lusk
s an
d i
n a
rth
rop
od
s (f
igu
re 5
0.4
b),
ther
e is
no
dis
tin
ctio
n
bet
wee
n t
he
circ
ula
tin
g f
luid
an
d t
he
extr
acel
lula
r fl
uid
of
the
bo
dy
tiss
ues
. Th
is f
luid
is
thu
s ca
lled
hem
oly
mp
h.
In
in
sect
s, a
mu
scu
lar
tub
e, o
r h
ear
t, p
um
ps
hem
oly
mp
h
thro
ug
h a
net
wo
rk o
f ch
ann
els
and
cav
itie
s in
th
e b
od
y. T
he
flu
id t
hen
dra
ins
bac
k in
to t
he
cen
tral
cav
ity.
Clo
sed
cir
cula
tory
sy
ste
ms
mo
ve
" u
ids
in a
loo
p
In a
clo
sed
cir
cula
tory
sys
tem
, th
e ci
rcu
lati
ng
flu
id,
blo
od
, is
al
way
s en
clo
sed
wit
hin
blo
od
ves
sels
th
at t
ran
spo
rt it
aw
ay fro
m
and
bac
k to
th
e h
eart
(fi
gu
re 5
0.4
c). S
om
e in
vert
ebra
tes,
su
ch a
s ce
ph
alo
po
d m
oll
usk
s an
d a
nn
elid
s (s
ee c
hap
ter
34
), a
nd
all
ver
-te
bra
tes
hav
e a
clo
sed
cir
cula
tory
sys
tem
.
In a
nn
elid
s su
ch a
s ea
rth
wo
rms,
a d
ors
al v
esse
l co
ntr
acts
rh
yth
mic
ally
to
fu
nct
ion
as
a p
um
p.
Blo
od
is
pu
shed
th
rou
gh
fi
ve s
mal
l co
nn
ecti
ng
art
erie
s, w
hic
h a
lso
fu
nct
ion
as
pu
mp
s, t
o
a ve
ntr
al v
esse
l, w
hic
h t
ran
spo
rts
the
blo
od
po
ster
iorl
y u
nti
l it
ev
entu
ally
ree
nte
rs t
he
do
rsal
ves
sel.
Sm
alle
r ve
ssel
s b
ran
ch
fro
m e
ach
art
ery
to s
up
ply
th
e ti
ssu
es o
f th
e ea
rth
wo
rm w
ith
o
xyg
en a
nd
nu
trie
nts
an
d t
o r
emo
ve w
aste
pro
du
cts.
Le
arn
ing
Ou
tco
me
s R
ev
iew
50
.2In
inve
rteb
rate
s, o
pen
circ
ulat
ory
syst
ems
pum
p he
mol
ymph
into
tiss
ues,
from
whi
ch it
then
dra
ins
into
a c
entr
al c
avit
y. C
lose
d ci
rcul
ator
y sy
stem
s
mov
e fl
uid
in a
loop
to a
nd fr
om a
mus
cula
r pum
ping
regi
on s
uch
as a
hea
rt.
Hem
olym
ph (i
nver
tebr
ates
) is
iden
tica
l to
the
extr
acel
lula
r fl u
id in
the
tiss
ues.
In
th
e o
pe
n c
ircu
lato
ry s
yste
m o
f in
sect
s, h
ow
do
es
he
mo
lym
ph
ge
t b
ack
to
th
e h
ea
rt?
Th
e ev
olu
tio
n o
f la
rge
and
co
mp
lex
hea
rts
and
clo
sed
cir
cula
-to
ry s
yste
ms
pu
t a
pre
miu
m o
n e
ffic
ien
t ci
rcu
lati
on
. In
re-
spo
nse
, ver
teb
rate
s h
ave
evo
lved
a r
emar
kab
le s
et o
f ad
apta
tio
ns
inex
tric
ably
lin
kin
g c
ircu
lati
on
an
d r
esp
irat
ion
, w
hic
h h
as f
a-ci
lita
ted
div
ersi
fica
tio
n t
hro
ug
ho
ut
aqu
atic
an
d t
erre
stri
al h
ab-
itat
s an
d p
erm
itte
d t
he
evo
luti
on
of
larg
e b
od
y si
ze.
In #
she
s, m
ore
e$
cie
nt
circ
ula
tio
n
de
ve
lop
ed
co
ncu
rre
ntl
y w
ith
gil
ls
Ch
ord
ates
an
cest
ral
to t
he
vert
ebra
tes
are
tho
ug
ht
to h
ave
had
si
mp
le t
ub
ula
r h
eart
s, s
imil
ar t
o t
ho
se n
ow
see
n in
lan
cele
ts (
see
chap
ter
35
). T
he
hea
rt w
as l
ittl
e m
ore
th
an a
sp
ecia
lize
d z
on
e o
f th
e ve
ntr
al a
rter
y th
at w
as m
ore
hea
vily
mu
scle
d t
han
th
e re
st o
f th
e ar
teri
es;
it c
on
trac
ted
in
sim
ple
per
ista
ltic
wav
es.
T
he
dev
elo
pm
ent
of
gil
ls b
y fi
shes
req
uir
ed a
mo
re e
ffi-
cien
t p
um
p,
and
in
fi
shes
w
e se
e th
e ev
olu
tio
n
of
a tr
ue
cham
ber
-pu
mp
hea
rt. T
he
fish
hea
rt i
s, i
n e
ssen
ce, a
tu
be
wit
h
fou
r st
ruct
ure
s ar
raye
d o
ne
afte
r th
e o
ther
to
fo
rm t
wo
pu
mp
-in
g c
ham
ber
s (f
igu
re 5
0.5
) . T
he
firs
t tw
o s
tru
ctu
res
the
sin
us
ven
osu
s an
d a
triu
m
form
th
e fi
rst
cham
ber
; th
e se
con
d t
wo
, th
e ve
ntr
icle
an
d c
on
us
arte
rio
sus,
fo
rm t
he
seco
nd
ch
amb
er.
Th
e si
nu
s ve
no
sus
is t
he
firs
t to
co
ntr
act,
foll
ow
ed b
y th
e at
riu
m,
the
ven
tric
le, a
nd
fin
ally
th
e co
nu
s ar
teri
osu
s.
Des
pit
e sh
ifts
in
th
e re
lati
ve p
osi
tio
ns
of
thes
e st
ruct
ure
s,
this
hea
rtb
eat
seq
uen
ce i
s m
ain
tain
ed i
n a
ll v
erte
bra
tes.
In
fis
h,
the
elec
tric
al i
mp
uls
e th
at p
rod
uce
s th
e co
ntr
acti
on
is
init
iate
d
in t
he
sin
us
ven
osu
s; in
oth
er v
erte
bra
tes,
th
e el
ectr
ical
imp
uls
e is
in
itia
ted
by
a st
ruct
ure
ho
mo
log
ou
s to
th
e si
nu
s ve
no
sus
the
sin
oat
rial
(S
A)
no
de.
A
fter
blo
od
lea
ves
the
con
us
arte
rio
sus,
it
mo
ves
thro
ug
h
the
gil
ls,
bec
om
ing
oxy
gen
ated
. B
loo
d l
eavi
ng
th
e g
ills
th
en
flo
ws
thro
ug
h a
net
wo
rk o
f ar
teri
es t
o t
he
rest
of
the
bo
dy,
fi-
nal
ly r
etu
rnin
g t
o t
he
sin
us
ven
osu
s. T
his
sim
ple
lo
op
has
on
e se
rio
us
lim
itat
ion
: in
pas
sin
g t
hro
ug
h t
he
cap
illa
ries
in
th
e g
ills
, blo
od
pre
ssu
re d
rop
s si
gn
ific
antl
y. T
his
slo
ws
circ
ula
tio
n
fro
m t
he
gil
ls t
o t
he
rest
of
the
bo
dy
and
can
lim
it o
xyg
en d
e-li
very
to
tis
sues
.
cha
pte
r 5
0
Th
e C
ircu
lato
ry S
yste
m
10
23
ww
w.r
av
en
bio
log
y.c
om
Apago PDF Enhancer
a.
b.
F .6+ 8 ,9 G % b % S
Y # W
W WN <
Y b L b W
S Y # L
In a
mp
hib
ian
s a
nd
mo
st r
ep
tile
s, lu
ng
s
req
uir
ed
a s
ep
ara
te c
ircu
lati
on
Th
e ad
ven
t o
f lu
ng
s in
am
ph
ibia
ns
(see
ch
apte
r 4
9)
invo
lved
a
maj
or
chan
ge
in t
he
pat
tern
of
circ
ula
tio
n,
a se
con
d p
um
pin
g
circ
uit
. Aft
er b
loo
d i
s p
um
ped
by
the
hea
rt t
hro
ug
h t
he
pulm
o-n
ary
arte
ries
to
th
e lu
ng
s, it
do
es n
ot
go
dir
ectl
y to
th
e ti
ssu
es o
f th
e b
od
y. I
nst
ead
, it
is
retu
rned
via
th
e pu
lmon
ary
vein
s to
th
e h
eart
. B
loo
d l
eave
s th
e h
eart
a s
eco
nd
tim
e to
be
circ
ula
ted
th
rou
gh
oth
er ti
ssu
es. T
his
syst
em is
term
ed d
ou
ble
cir
cula
tio
n:
On
e sy
stem
, th
e p
ulm
on
ary
circ
ula
tio
n, m
ove
s b
loo
d b
etw
een
h
eart
an
d l
un
gs,
an
d a
no
ther
, th
e sy
stem
ic c
ircu
lati
on
, m
ove
s b
loo
d b
etw
een
th
e h
eart
an
d t
he
rest
of
the
bo
dy.
Am
ph
ibia
n c
ircu
lati
on
Op
tim
ally
, o
xyg
enat
ed b
loo
d f
rom
lu
ng
s w
ou
ld g
o d
irec
tly
to
tiss
ues
, ra
ther
th
an b
ein
g m
ixed
in
th
e h
eart
wit
h d
eoxy
gen
-at
ed b
loo
d r
etu
rnin
g f
rom
th
e b
od
y. T
he
amp
hib
ian
hea
rt h
as
two
str
uct
ura
l fe
atu
res
that
sig
nif
ican
tly
red
uce
th
is m
ixin
g
(fig
ure
50
.6) .
Fir
st,
the
atri
um
is
div
ided
in
to t
wo
ch
amb
ers:
T
he
rig
ht
atri
um
rec
eive
s d
eoxy
gen
ated
blo
od
fro
m t
he
sys-
tem
ic
circ
ula
tio
n,
and
th
e le
ft
atri
um
re
ceiv
es
oxy
gen
ated
b
loo
d f
rom
th
e lu
ng
s. T
hes
e tw
o t
ypes
of
blo
od
, th
eref
ore
, do
n
ot
mix
in
th
e at
ria.
B
ecau
se a
n a
mp
hib
ian
hea
rt h
as a
sin
gle
ven
tric
le,
the
sep
arat
ion
of
the
pu
lmo
nar
y an
d s
yste
mic
cir
cula
tio
ns
is i
n-
com
ple
te.
Th
e ex
ten
t o
f m
ixin
g w
hen
th
e co
nte
nts
of
each
at
riu
m e
nte
r th
e ve
ntr
icle
is
red
uce
d b
y in
tern
al c
han
nel
s cr
e-at
ed b
y re
cess
es i
n t
he
ven
tric
ula
r w
all.
Th
e co
nu
s ar
teri
osu
s is
p
arti
ally
sep
arat
ed b
y a
div
idin
g w
all,
wh
ich
dir
ects
deo
xyg
en-
ated
blo
od
in
to t
he
pu
lmo
nar
y ar
teri
es a
nd
oxy
gen
ated
blo
od
in
to t
he
aort
a, t
he
maj
or
arte
ry o
f th
e sy
stem
ic c
ircu
lati
on
.
Am
ph
ibia
ns
livi
ng
in
wat
er c
an o
bta
in a
dd
itio
nal
oxy
gen
b
y d
iffu
sio
n t
hro
ug
h t
hei
r sk
in. T
hu
s, a
mp
hib
ian
s h
ave
a pu
lmo-
cuta
neo
us
circ
uit
th
at s
end
s b
loo
d t
o b
oth
th
e lu
ng
s an
d t
he
skin
. C
uta
neo
us
resp
irat
ion
is a
lso
see
n in
man
y aq
uat
ic r
epti
les
such
as
tu
rtle
s.
Re
pti
lia
n c
ircu
lati
on
Am
on
g r
epti
les,
ad
dit
ion
al m
od
ific
atio
ns
hav
e fu
rth
er r
edu
ced
th
e m
ixin
g o
f b
loo
d in
th
e h
eart
. In
ad
dit
ion
to
hav
ing
tw
o s
ep-
arat
e at
ria,
rep
tile
s h
ave
a se
ptu
m t
hat
par
tial
ly s
ub
div
ides
th
e ve
ntr
icle
. Th
is s
epar
atio
n i
s co
mp
lete
in
on
e o
rder
of
rep
tile
s,
the
cro
cod
ilia
ns,
wh
ich
hav
e tw
o s
epar
ate
ven
tric
les
div
ided
by
a co
mp
lete
sep
tum
(se
e th
e fo
llo
win
g s
ecti
on
). A
no
ther
ch
ang
e in
th
e ci
rcu
lati
on
of
rep
tile
s is
th
at t
he
con
us
arte
rio
sus
has
b
eco
me
inco
rpo
rate
d i
nto
th
e tr
un
ks o
f th
e la
rge
arte
ries
lea
v-in
g t
he
hea
rt.
Fig
ure
50
.6 T
he
he
art
an
d c
ircu
lati
on
of
an
am
ph
ibia
n.
a.
Th
e fr
og
has
a t
hre
e-ch
amb
ered
hea
rt w
ith
tw
o a
tria
bu
t o
nly
on
e
ven
tric
le, w
hic
h p
um
ps
blo
od
bo
th t
o t
he
lun
gs
and
to
th
e b
od
y. b
. D
esp
ite
the
po
ten
tial
fo
r m
ixin
g, t
he
oxy
gen
ated
an
d d
eoxy
gen
ated
blo
od
s
(red
an
d b
lue
lin
es, re
spec
tive
ly)
mix
lit
tle
as t
hey
are
pu
mp
ed t
o t
he
bo
dy
and
lu
ng
s. O
xyg
enat
ion
of
blo
od
als
o o
ccu
rs b
y g
as e
xch
ang
e
thro
ug
h t
he
skin
.
10
24
p
art
VII
An
ima
l Fo
rm a
nd
Fu
nct
ion
Apago PDF Enhancer
Head
Body
Lungs
Systemic
capillaries
Pulm
onary
artery
Pulm
onary
semilu
nar va
lve
Inferior
vena cava
Superior
vena cava
Aorta
Tricuspid valve
Right ve
ntricle
Left
ventricle
Right atrium
Pulm
onary
veins
Left atrium
Bicuspid
mitral
valve
Systemic
capillaries
Pulm
onary
artery
Superior
vena cava
Inferior
vena cava
Artery
Pulm
onary
vein
Aorta
Respiratory
capillaries
a.
b.
Ma
mm
als
, bir
ds,
an
d c
roco
dil
ian
s h
av
e t
wo
com
ple
tely
se
pa
rate
d c
ircu
lato
ry s
yst
em
s
Mam
mal
s, b
ird
s, a
nd
cro
cod
ilia
ns
hav
e a
fou
r-ch
amb
ered
hea
rt
wit
h t
wo
sep
arat
e at
ria
and
tw
o s
epar
ate
ven
tric
les
(fig
ure
50
.7) .
T
he
hea
rts
of
bir
ds
and
cro
cod
iles
exh
ibit
so
me
dif
fere
nce
s, b
ut
ove
rall
are
qu
ite
sim
ilar
, w
hic
h i
s n
ot
surp
risi
ng
giv
en t
hei
r cl
ose
evo
luti
on
ary
rela
tio
nsh
ip (
fig
ure
50
.8) .
Ho
wev
er,
the
ex-
trem
e si
mil
arit
y o
f th
e h
eart
s o
f b
ird
s an
d m
amm
als
so a
like
th
at a
sin
gle
ill
ust
rati
on
can
su
ffic
e fo
r b
oth
(se
e fi
gu
re 5
0.7
)is
a r
emar
kab
le c
ase
of
con
verg
ent
evo
luti
on
(se
e fi
gu
re 5
0.8
).
In
a f
ou
r-ch
amb
ered
hea
rt,
the
rig
ht
atri
um
rec
eive
s d
e-o
xyg
enat
ed b
loo
d f
rom
th
e b
od
y an
d d
eliv
ers
it t
o t
he
rig
ht
ven
tric
le, w
hic
h p
um
ps
the
blo
od
to
th
e lu
ng
s. T
he
left
atr
ium
re
ceiv
es o
xyg
enat
ed b
loo
d f
rom
th
e lu
ng
s an
d d
eliv
ers
it t
o t
he
left
ven
tric
le, w
hic
h p
um
ps
the
oxy
gen
ated
blo
od
to
th
e re
st o
f th
e b
od
y (s
ee f
igu
re 5
0.7
).
Th
e h
eart
in
th
ese
vert
ebra
tes
is a
tw
o-c
ycle
pu
mp
. Bo
th
atri
a fi
ll w
ith
blo
od
an
d s
imu
ltan
eou
sly
con
trac
t, e
mp
tyin
g
thei
r b
loo
d i
nto
th
e ve
ntr
icle
s. B
oth
ven
tric
les
also
co
ntr
act
at
the
sam
e ti
me,
pu
shin
g b
loo
d s
imu
ltan
eou
sly
into
th
e p
ulm
o-
nar
y an
d s
yste
mic
cir
cula
tio
ns.
T
he
incr
ease
d e
ffic
ien
cy o
f th
e d
ou
ble
cir
cula
tory
sys
tem
in
mam
mal
s an
d b
ird
s is
th
ou
gh
t to
hav
e b
een
im
po
rtan
t in
th
e ev
olu
tio
n o
f en
do
ther
my.
Mo
re e
ffic
ien
t ci
rcu
lati
on
is
nec
es-
sary
to
su
pp
ort
th
e h
igh
met
abo
lic
rate
req
uir
ed f
or
mai
nte
-n
ance
of
inte
rnal
bo
dy
tem
per
atu
re a
bo
ut
a se
t p
oin
t.
Th
rough
out t
he
evolu
tion
ary
his
tory
of t
he
vert
ebra
te h
eart
, th
e si
nus
ven
osu
s h
as s
erve
d a
s a
pac
emak
er,
the
site
wh
ere
the
impuls
es t
hat
in
itia
te t
he
hea
rtbea
t ori
gin
ate.
Alt
hough
th
e si
nus
ven
osu
s co
nst
itute
s a
maj
or
cham
ber
in t
he
fish
hea
rt, i
t is
red
uce
d
in s
ize
in a
mph
ibia
ns
and i
s fu
rth
er r
educe
d i
n r
epti
les.
In
mam
-m
als
and b
irds,
th
e si
nus
ven
osu
s is
no lo
nge
r pre
sen
t as
a s
epar
ate
cham
ber
, al
though
som
e of
its
tiss
ue
rem
ain
s in
th
e w
all
of
the
righ
t at
rium
. Th
is t
issu
e, t
he
sin
oat
rial
(S
A)
node,
is
still
the
site
w
her
e ea
ch h
eart
bea
t ori
gin
ates
as
det
aile
d la
ter
in t
he
chap
ter.
Le
arn
ing
Ou
tco
me
s R
ev
iew
50
.3
The
chor
date
hea
rt h
as e
volv
ed fr
om a
mus
cula
r reg
ion
of a
ves
sel,
to th
e
two-
cham
bere
d he
art o
f fi s
h, th
e th
ree-
cham
bere
d he
art o
f am
phib
ians
and
mos
t rep
tile
s, a
nd th
e fo
ur-c
ham
bere
d he
art o
f cro
codi
lians
, bir
ds, a
nd
mam
mal
s. D
eoxy
gena
ted
bloo
d tr
avel
s in
the
pulm
onar
y ci
rcui
t fro
m th
e
righ
t atr
ium
into
the
righ
t ven
tric
le a
nd th
en to
the
lung
s; it
retu
rns
to
the
left
atr
ium
. Oxy
gena
ted
bloo
d tr
avel
s in
the
syst
emic
cir
cuit
from
the
left
atr
ium
into
the
left
ven
tric
le a
nd th
en to
the
body
; it r
etur
ns to
the
righ
t atr
ium
.
W
ha
t is
th
e p
hys
iolo
gic
al a
dva
nta
ge
of
ha
vin
g
sep
ara
ted
ve
ntr
icle
s?
Fig
ure
50
.7T
he
he
art
an
d c
ircu
lati
on
of
ma
mm
als
an
d b
ird
s.
a.
Th
e p
ath
of
blo
od
th
rou
gh
th
e fo
ur-
cham
ber
ed h
eart
. b.
Th
e
rig
ht
sid
e o
f th
e h
eart
rec
eive
s d
eoxy
gen
ated
blo
od
an
d p
um
ps
it t
o t
he
lun
gs;
th
e le
ft s
ide
of
the
hea
rt r
ecei
ves
oxy
gen
ated
blo
od
an
d p
um
ps
it
to t
he
bo
dy.
In
th
is w
ay,
the
pu
lmo
nar
y an
d s
yste
mic
cir
cula
tio
ns
are
kep
t co
mp
lete
ly s
epar
ate.
cha
pte
r 5
0
Th
e C
ircu
lato
ry S
yste
m
10
25
ww
w.r
av
en
bio
log
y.c
om
Apago PDF Enhancer c = c c
c
F 16H)- )' +d5 +(I 1331- +e .*'- )+f 34(5g5 16+; *,H,95-5 16+J h.131' )+85 *9 +
Fig
ure
50
.8
Ev
olu
tio
n o
f th
e
he
art
in
ve
rte
bra
tes.
Des
pit
e th
eir
sim
ilar
ity,
the
fou
r-ch
amb
ered
hea
rts
of
mam
mal
s
and
bir
ds
evo
lved
con
verg
entl
y.
5
0.4
Th
e Fo
ur-
Ch
am
ber
ed H
eart
a
nd
th
e B
loo
d V
esse
ls
Le
arn
ing
Ou
tco
me
s
Exp
lain
th
e ca
rdia
c cy
cle
.1.
De
scri
be
the
role
of
au
torh
yth
mic
ce
lls
of
the
SA
no
de
.2
.
De
fin
e b
loo
d p
ress
ure
an
d h
ow
it is
me
asu
red
3.
As
men
tio
ned
ear
lier
, th
e h
eart
of
mam
mal
s, b
ird
s, a
nd
cro
co-
dil
ian
s g
oes
th
rou
gh
tw
o c
on
trac
tio
n c
ycle
s, o
ne
of
atri
al c
on
-tr
acti
on
to
sen
d b
loo
d t
o t
he
ven
tric
les,
an
d o
ne
of
ven
tric
ula
r co
ntr
acti
on
to
sen
d b
loo
d t
o t
he
pu
lmo
nar
y an
d s
yste
mic
cir
-cu
its.
Th
ese
two
co
ntr
acti
on
s p
lus
the
rest
ing
per
iod
bet
wee
n
thes
e m
ake
up
th
e co
mp
lete
car
dia
c cy
cle
en
com
pas
sed
by
the
hea
rtb
eat.
Th
e c
ard
iac
cycl
e d
riv
es
the
ca
rdio
va
scu
lar
syst
em
Th
e h
eart
has
tw
o p
airs
of v
alve
s. O
ne
pai
r, th
e at
riove
ntr
icu
lar
(AV
) va
lves,
mai
nta
ins
un
idir
ecti
on
al b
loo
d f
low
bet
wee
n t
he
atri
a an
d v
entr
icle
s. T
he
AV
val
ve o
n t
he
rig
ht
sid
e is
th
e tr
icu
spid
val
ve, a
nd
th
e A
V v
alve
on
th
e le
ft is
th
e b
icu
spid
, or
mit
ral,
valv
e.
An
oth
er
pai
r o
f va
lves
, to
get
her
ca
lled
th
e se
mil
un
ar v
alve
s, e
nsu
re o
ne-
way
flo
w o
ut
of
the
ven
tric
les
to
the
arte
rial
sys
tem
s. T
he
pu
lmo
nar
y va
lve
is lo
cate
d a
t th
e ex
it
of
the
rig
ht
ven
tric
le, a
nd
th
e ao
rtic
val
ve i
s lo
cate
d a
t th
e ex
it
of
the
left
ven
tric
le.
Th
ese
valv
es o
pen
an
d c
lose
as
the
hea
rt
go
es t
hro
ug
h it
s cy
cle.
Th
e cl
osi
ng
of
thes
e va
lves
pro
du
ces
the
lu
b-d
ub
so
un
ds
hea
rd w
ith
a s
teth
osc
op
e.
T
he
card
iac
cycl
e is
po
rtra
yed
in
fig
ure
50
.9 . I
t b
egin
s as
b
loo
d r
etu
rns
to t
he
rest
ing
hea
rt t
hro
ug
h v
ein
s th
at e
mp
ty
into
th
e ri
gh
t an
d l
eft
atri
a. A
s th
e at
ria
fill
an
d t
he
pre
ssu
re i
n
them
ris
es,
the
AV
val
ves
op
en a
nd
blo
od
flo
ws
into
th
e ve
n-
tric
les.
Th
e ve
ntr
icle
s b
eco
me
abo
ut
80
% f
ille
d d
uri
ng
th
is
tim
e. C
on
trac
tio
n o
f th
e at
ria
top
s u
p t
he
fin
al 2
0%
of
the
80
mL
of
blo
od
th
e ve
ntr
icle
s re
ceiv
e, o
n a
vera
ge,
in
a r
esti
ng
p
erso
n. T
hes
e ev
ents
occ
ur
wh
ile
the
ven
tric
les
are
rela
xin
g,
a p
erio
d c
alle
d v
entr
icu
lar
dia
sto
le.
A
fter
a s
ligh
t d
elay
, th
e ve
ntr
icle
s co
ntr
act,
a p
erio
d c
alle
d
ven
tric
ula
r sy
sto
le.
Co
ntr
acti
on
of
each
ven
tric
le i
ncr
ease
s th
e p
ress
ure
wit
hin
eac
h c
ham
ber
, ca
usi
ng t
he
AV
val
ves
to f
orc
e-fu
lly
clo
se (
the
lu
b
sou
nd
), p
reve
nti
ng b
loo
d f
rom
bac
kin
g u
p
into
th
e at
ria.
Im
med
iate
ly a
fter
th
e A
V v
alve
s cl
ose
, th
e p
res-
sure
in t
he
ven
tric
les
forc
es t
he
sem
ilu
nar
val
ves
op
en a
nd
blo
od
fl
ow
s in
to t
he
arte
rial
sys
tem
s. A
s th
e ve
ntr
icle
s re
lax,
clo
sin
g o
f th
e se
mil
un
ar v
alve
s p
reve
nts
bac
kflo
w (
the
du
b
sou
nd
).
Co
ntr
act
ion
of
he
art
mu
scle
is
init
iate
d b
y a
uto
rhy
thm
ic c
ell
s
As
in o
ther
typ
es o
f m
uscl
e, c
ontr
acti
on o
f h
eart
mus
cle
is s
tim
u-la
ted
by m
embr
ane
depo
lari
zati
on (s
ee c
hap
ters
44
and
47).
In s
kel-
etal
mus
cles
, on
ly n
erve
impu
lses
from
mot
or n
euro
ns ca
n n
orm
ally
in
itia
te d
epol
ariz
atio
n. T
he
hea
rt, b
y co
ntr
ast,
con
tain
s sp
ecia
lized
s
elf-
exci
tabl
e m
uscl
e ce
lls c
alle
d au
torh
yth
mic
fib
ers,
wh
ich
can
in
itia
te p
erio
dic
acti
on p
oten
tial
s w
ith
out
neu
ral a
ctiv
atio
n.
T
he
mo
st i
mp
ort
ant
gro
up
of
auto
rhyt
hm
ic c
ells
is
the
sin
oat
rial
(S
A)
no
de,
des
crib
ed e
arli
er (
fig
ure
50
.10
) . L
oca
ted
in
th
e w
all
of
the
rig
ht
atri
um
, th
e S
A n
od
e ac
ts a
s a
pac
emak
er
for
the
rest
of
the
hea
rt b
y p
rod
uci
ng
sp
on
tan
eou
s ac
tio
n p
o-
ten
tial
s at
a f
aste
r ra
te t
han
oth
er a
uto
rhyt
hm
ic c
ells
. T
hes
e sp
on
tan
eou
s ac
tio
n p
ote
nti
als
are
du
e to
a c
on
stan
t le
akag
e o
f N
a+ io
ns
into
th
e ce
ll t
hat
dep
ola
rize
th
e m
emb
ran
e. W
hen
th
e
10
26
p
art
VII
An
ima
l Fo
rm a
nd
Fu
nct
ion
Apago PDF Enhancer
Apago PDF Enhancer
F ig
ure
50
.10
Th
e p
ath
of
ele
ctr
ica
l e
xci
tati
on
in
th
e
he
art
. T
he
even
ts o
ccu
rrin
g d
uri
ng
co
ntr
acti
on
of
the
hea
rt a
re
corr
elat
ed w
ith
th
e m
easu
rem
ent
of
elec
tric
al a
ctiv
ity
by
an
elec
tro
card
iog
ram
(E
CG
als
o c
alle
d E
KG
). T
he
dep
ola
riza
tio
n/
con
trac
tio
n o
f th
e at
riu
m i
s sh
ow
n i
n g
reen
ab
ove
an
d c
orr
esp
on
ds
to t
he
P w
ave
of
the
EC
G (
also
in
gre
en).
Th
e d
epo
lari
zati
on
/
con
trac
tio
n o
f th
e ve
ntr
icle
is
sho
wn
in
red
ab
ove
an
d c
orr
esp
on
ds
to t
he
QR
S w
ave
of
the
EC
G (
also
in
red
). T
he
T w
ave
on
th
e E
CG
corr
esp
on
ds
to t
he
rep
ola
riza
tio
n o
f th
e ve
ntr
icle
s. T
he
atri
al
rep
ola
riza
tio
n i
s m
aske
d b
y th
e Q
RS
wav
e.
rem
ove
d f
rom
th
e cy
topla
sm b
y a
pum
p i
n t
he
sarc
opla
smic
re-
ticu
lum
sim
ilar
to s
kele
tal m
usc
le, a
nd a
n a
ddit
ion
al c
arri
er in
th
e pla
sma
mem
bra
ne
pum
ps
Ca2+
into
th
e in
ters
titi
al s
pac
e.
Th
e el
ectr
ical
act
ivit
y o
f th
e h
eart
can
be
reco
rded
fro
m
the
surf
ace
of
the
bo
dy
wit
h e
lect
rod
es p
lace
d o
n t
he
lim
bs
and
ch
est.
Th
e re
cord
ing,
ca
lled
an
el
ectr
oca
rdio
gram
(E
CG
o
r E
KG
), s
ho
ws
ho
w t
he
cell
s o
f th
e h
eart
dep
ola
rize
an
d r
epo
lari
ze
du
rin
g th
e ca
rdia
c cy
cle
(see
fig
ure
50.
10). D
epo
lari
zati
on
cau
ses
con
trac
tio
n o
f th
e h
eart
, an
d r
epo
lari
zati
on
cau
ses
rela
xati
on
.
Th
e fi
rst
pea
k in
th
e re
cord
ing
, P, i
s p
rod
uce
d b
y th
e d
e-p
ola
riza
tio
n o
f th
e at
ria,
an
d i
s as
soci
ated
wit
h a
tria
l sy
sto
le.
Th
e se
con
d,
larg
er p
eak,
QR
S,
is p
rod
uce
d b
y ve
ntr
icu
lar
de-
po
lari
zati
on
; du
rin
g t
his
tim
e, t
he
ven
tric
les
con
trac
t (v
entr
icu
-la
r sy
sto
le).
T
he
last
p
eak,
T
, is
p
rod
uce
d
by
ven
tric
ula
r re
po
lari
zati
on
; at
th
is t
ime,
th
e ve
ntr
icle
s b
egin
dia
sto
le.
Art
eri
es
an
d v
ein
s b
ran
ch t
o
an
d f
rom
all
pa
rts
of
the
bo
dy
Th
e ri
ght
and
lef
t p
ulm
on
ary
arte
ries
del
iver
oxy
gen
-dep
lete
d
blo
od
fro
m t
he
rig
ht
ven
tric
le t
o t
he
rig
ht
and
lef
t lu
ng
s. A
s
10
28
p
art
VII
An
ima
l Fo
rm a
nd
Fu
nct
ion
Apago PDF Enhancer
Fig
ure
50
.11
Me
asu
rem
en
t o
f b
loo
d p
ress
ure
. T
he
blo
od
pre
ssu
re c
uff
is
tigh
ten
ed t
o s
top
th
e b
loo
d !
ow
th
rou
gh
th
e b
rach
ial
arte
ry. A
s th
e cu
ff i
s lo
ose
ned
, th
e m
axim
al (
syst
oli
c) p
ress
ure
bec
om
es g
reat
er t
han
th
e cu
ff p
ress
ure
an
d b
loo
d c
an m
om
enta
rily
pas
s th
rou
gh
,
pro
du
cin
g a
pu
lse
that
can
be
hea
rd w
ith
a s
teth
osc
op
e. T
he
pre
ssu
re a
t th
is p
oin
t is
rec
ord
ed a
s th
e sy
sto
lic
pre
ssu
re. A
s th
e cu
ff p
ress
ure
con
tin
ues
to
dro
p, b
loo
d p
ress
ure
is
gre
ater
th
an c
uff
pre
ssu
re f
or
larg
er p
ort
ion
s o
f th
e ca
rdia
c cy
cle.
Eve
ntu
ally
, eve
n t
he
min
imu
m p
ress
ure
du
rin
g t
he
cycl
e is
gre
ater
th
an t
he
cuff
pre
ssu
re, a
t w
hic
h t
ime
the
blo
od
ves
sel
is n
o l
on
ger
dis
tort
ed a
nd
sil
ent
lam
inar
! o
w r
etu
rns,
rep
laci
ng
the
pu
lsin
g s
ou
nd
. Th
e d
iast
oli
c p
ress
ure
is
reco
rded
as
the
pre
ssu
re a
t w
hic
h a
so
un
d i
s n
o l
on
ger
hea
rd.
pre
vio
usl
y m
enti
on
ed, t
he
pu
lmo
nar
y ve
ins
retu
rn o
xyg
enat
ed
blo
od
fro
m t
he
lun
gs
to t
he
left
atr
ium
of
the
hea
rt.
T
he
aort
a an
d a
ll i
ts b
ran
ches
are
sys
tem
ic a
rter
ies,
car
-ry
ing
oxy
gen
-ric
h b
loo
d f
rom
th
e le
ft v
entr
icle
to
all
par
ts o
f th
e b
od
y. T
he
coro
nar
y ar
teri
es
are
the
firs
t b
ran
ches
off
th
e ao
rta;
th
ese
sup
ply
oxy
gen
ated
blo
od
to
th
e h
eart
mu
scle
its
elf
(see
fig
ure
50
.7b )
. O
ther
sys
tem
ic a
rter
ies
bra
nch
fro
m t
he
aort
a as
it m
akes
an
arc
h a
bo
ve t
he
hea
rt a
nd
as
it d
esce
nd
s an
d
trav
erse
s th
e th
ora
cic
and
ab
do
min
al c
avit
ies.
T
he
blo
od
fro
m t
he
bo
dy
s o
rgan
s, n
ow
lo
wer
in
oxy
gen
, re
turn
s to
th
e h
eart
in
th
e sy
stem
ic v
ein
s. T
hes
e ev
entu
ally
em
pty
in
to t
wo
maj
or
vein
s: t
he
sup
eri
or
ven
a ca
va,
wh
ich
d
rain
s th
e u
pp
er b
od
y, a
nd
th
e in
feri
or
ven
a ca
va, w
hic
h d
rain
s th
e lo
wer
bo
dy.
Th
ese
vein
s em
pty
in
to t
he
rig
ht
atri
um
, co
m-
ple
tin
g t
he
syst
emic
cir
cula
tio
n.
T
he
flo
w o
f b
loo
d t
hro
ug
h t
he
arte
ries
, ca
pil
lari
es,
and
ve
ins
is d
rive
n b
y th
e p
ress
ure
gen
erat
ed b
y ve
ntr
icu
lar
con
-tr
acti
on
. T
he
ven
tric
les
mu
st c
on
trac
t fo
rcef
ull
y en
ou
gh
to
m
ove
th
e b
loo
d t
hro
ug
h t
he
enti
re c
ircu
lato
ry s
yste
m.
Art
eri
al b
loo
d p
ress
ure
ca
n b
e m
ea
sure
d
As
the
ven
tric
les
con
trac
t, g
reat
pre
ssu
re i
s g
ener
ated
wit
hin
th
em a
nd
tra
nsf
erre
d t
hro
ug
h t
he
arte
ries
on
ce t
he
aort
ic
valv
e o
pen
s. T
he
pu
lse
that
yo
u c
an d
etec
t in
yo
ur
wri
st o
r
nec
k r
esu
lts
fro
m c
han
ges
in
pre
ssu
re a
s el
asti
c ar
teri
es e
x-p
and
an
d c
on
trac
t w
ith
th
e p
erio
dic
blo
od
flo
w.
Do
cto
rs u
se
blo
od
p
ress
ure
as
an
g
ener
al
ind
icat
or
of
card
iova
scu
lar
hea
lth
bec
ause
a v
arie
ty o
f co
nd
itio
ns
can
cau
se i
ncr
ease
s o
r d
ecre
ases
in
pre
ssu
re.
A
sph
ygm
oman
omet
er m
easu
res
the
blo
od
pre
ssu
re i
n t
he
bra
chia
l ar
tery
fo
un
d o
n t
he
insi
de
par
t o
f th
e ar
m, a
bo
ve t
he
elb
ow
(fi
gu
re 5
0.1
1) .
A c
uff
wra
pp
ed a
rou
nd
th
e u
pp
er p
art
of
the
arm
is
tig
hte
ned
en
ou
gh
to
sto
p t
he
flo
w o
f b
loo
d t
o t
he
low
er p
art
of
the
arm
. As
the
cuff
is
slo
wly
lo
ose
ned
, ev
entu
-al
ly t
he
blo
od
pre
ssu
re p
rod
uce
d b
y th
e h
eart
is
gre
ater
th
an
the
con
stri
ctin
g p
ress
ure
of
cuff
an
d b
loo
d b
egin
s p
uls
atin
g
thro
ug
h t
he
arte
ry,
pro
du
cin
g a
so
un
d t
hat
can
be
det
ecte
d
usi
ng
a s
teth
osc
op
e. T
he
po
int
at w
hic
h t
his
pu
lsin
g s
ou
nd
b
egin
s m
arks
th
e p
eak
pre
ssu
re,
or
syst
oli
c p
ress
ure
, at
w
hic
h v
entr
icle
s ar
e co
ntr
acti
ng
. A
s th
e cu
ff i
s lo
ose
ned
fu
r-th
er,
the
po
int
is r
each
ed w
her
e th
e p
ress
ure
of
the
cuff
is
low
er t
han
th
e b
loo
d p
ress
ure
th
rou
gh
ou
t th
e ca
rdia
c cy
cle,
at
wh
ich
tim
e th
e b
loo
d v
esse
l is
no
lo
ng
er d
isto
rted
an
d t
he
pu
lsin
g s
ou
nd
sto
ps.
Th
is p
oin
t m
arks
th
e m
inim
um
pre
ssu
re
bet
wee
n h
eart
bea
ts o
r d
iast
oli
c p
ress
ure
, at
wh
ich
th
e ve
n-
tric
les
are
rela
xed
.
Th
e b
loo
d p
ress
ure
is
wri
tten
as
a ra
tio
of
syst
oli
c o
ver
dia
sto
lic
pre
ssu
re, a
nd
fo
r a
hea
lth
y p
erso
n i
n h
is o
r h
er t
wen
-ti
es, a
typ
ical
blo
od
pre
ssu
re is
12
0/7
5 (
mea
sure
d in
mil
lim
eter
s
cha
pte
r 5
0
Th
e C
ircu
lato
ry S
yste
m
10
29
ww
w.r
av
en
bio
log
y.c
om
Apago PDF Enhancer
a.
b.
c.
Fig
ure
50
.12
Th
e
stru
ctu
re o
f b
loo
d
ve
sse
ls.
Art
erie
s (a
)
and
vei
ns
(b)
hav
e th
e
sam
e ti
ssu
e la
yers
, b
ut
the
smo
oth
mu
scle
lay
er
in a
rter
ies
is m
uch
thic
ker
and
th
ere
are
two
ela
stic
lay
ers.
c. C
apil
lari
es a
re
com
po
sed
of
on
ly a
sin
gle
lay
er o
f
end
oth
elia
l ce
lls.
(No
t to
sca
le.)
of
mer
cury
, o
r m
m
Hg
).
Th
e m
edic
al
con
dit
ion
ca
lled
h
ypert
en
sio
n (
hig
h b
loo
d p
ress
ure
) is
def
ined
as
eith
er a
sys
-to
lic
pre
ssu
re g
reat
er t
han
15
0 m
m H
g o
r a
dia
sto
lic
pre
ssu
re
gre
ater
th
an 9
0 m
m H
g.
Le
arn
ing
Ou
tco
me
s R
ev
iew
50
.4Th
e ca
rdia
c cy
cle
cons
ists
of s
ysto
le a
nd d
iast
ole;
the
vent
ricl
es c
ontr
act
at s
ysto
le a
nd re
lax
at d
iast
ole.
The
SA
node
in th
e ri
ght a
triu
m in
itia
tes
wav
es o
f