The Cardiovascular System: Moving Blood...
10
YOUR heart is the most durable muscle in your body. It begins beating about a month after conception and keeps going for a lifetime. A natural “pacemaker” in the heart’s wall produces an electrical signal that stimulates each heartbeat. If this pacemaker malfunctions, the heart may stop beating—an event called sudden cardiac arrest. Each year more than 300,000 people in the United States suffer sudden cardiac arrest. In older people, heart disease is the usual cause. In those under age 35, an inborn heart defect often is to blame. This was the case with Matt Nader, the young man shown at left. He went into sudden cardiac arrest while playing in a high school football game. Matt’s parents, who were watching the game, rushed onto the field and started cardiopulmonary resuscitation (CPR) on their lifeless son. In CPR, a person alternates mouth-to-mouth respiration with chest compressions that keep the victim’s blood moving. If CPR is started within 4 to 6 minutes, the victim’s chances of surviving the arrest rise by 50 percent. CPR does not restart a stopped heart. That requires a device called a defibrillator, which delivers a strong electric current to the chest. With luck the shock quickly restarts the pacemaker. In Matt’s case, a bystander ran to get the school’s automated external defibrillator (AED). This device, about the size of a laptop computer, provides simple voice instructions on its use and if need be generates a shock. Such a procedure helped save Matt Nader. The public health value of AEDs now is widely recognized. Many schools, senior centers, shopping malls, hotels, and airports keep one of these lifesavers on hand. In this chapter you will learn about the structure and function of the cardiovascular system—the heart and blood vessels. Several topics will help you to understand the biology that underlies CPR and the use of an AED. If you would like to learn how to save lives with these methods, the American Heart Association, the American Red Cross, and many other community organizations provide training. Taking time to learn these skill is something we all can do for one another. 121 LINKS TO EARLIER CONCEPTS • This chapter begins our study of the body’s major internal organ systems and how each contributes to homeostasis. It looks more closely at cardiac muscle (4.3) and at the specialized cell junctions in this tissue (4.6). • You will see how the tubelike organs called blood vessels are built from layers of epithelium, connective tissue, and smooth muscle (4.1–4.3). • We also consider cardiovascular diseases and disorders, including links between heart health and lipoproteins and cholesterol (2.10, 2.12). How Would You Vote? Some advocates think that CPR training should be a required mini-course in high schools. People who learn CPR also must be periodically recertified. Would you favor mandatory CPR training in high schools? See CengageNOW for details, then vote online. KEY CONCEPTS Circulating Blood The cardiovascular system transports oxygen, nutrients, hormones, and other substances swiftly to body cells. It also carries away wastes and cell products. Section 7.1 Pumping Blood The heart is a muscular pump. Heart contractions provide the force that drives blood through the cardiovascular system’s arteries and veins. Sections 7.2–7.5 Blood Vessels Various types of blood vessels, including arteries, arterioles, capillaries, venules, and veins, are specialized for different blood transport functions. Sections 7.6–7.9 Disorders of the Circulatory System and Homeostasis Sections 7.8–7.10 Circulation: The Heart and Blood Vessels 7 Be Not Still, My Beating Heart! IMPACTS, ISSUES 122 CHAPTER 7 The Cardiovascular System: Moving Blood through the Body 7.1 The cardiovascular system is built to rapidly transport blood to every living cell in the body. Links to Diffusion 3.10, Metabolism 3.13 Figure 7.1 Animated! The heart and blood vessels make up the cardiovascular system. Arteries, which carry oxygenated blood to tissues, are shaded red. Veins, which carry deoxygenated blood away from tissues, are shaded blue. Notice, however, that for the pulmonary arteries and veins the roles are reversed. Carries blood that has passed through small intestine and then liver Jugular Veins Receive blood from brain and from tissues of head Superior Vena Cava Receives blood from veins of upper body Pulmonary Veins Deliver oxygenated blood from the lungs to the heart Hepatic Vein Renal Vein Carries processed blood away from kidneys Inferior Vena Cava Receives blood from all veins below diaphragm Iliac Veins Carry blood away from the pelvic organs and lower abdominal wall Femoral Vein Carries blood away from the thigh and inner knee Carotid Arteries Deliver blood to neck, head, brain Ascending Aorta Carries oxygenated blood away from heart; the largest artery Pulmonary Arteries Deliver oxygen-poor blood from the heart to the lungs Coronary Arteries Service the cardiac muscle cells of heart Brachial Artery Delivers blood to upper limbs; blood pressure measured here Renal Artery Delivers blood to kidneys, where its volume, chemical make up are adjusted Abdominal Aorta Delivers blood to arteries leading to the digestive tract, kidneys, pelvic organs, lower limbs Iliac Arteries Deliver blood to pelvic organs and lower abdominal wall Femoral Artery Delivers blood to the thigh and inner knee
Transcript of The Cardiovascular System: Moving Blood...
YOUR
heart
is t
he m
ost
dura
ble
muscle
in y
our
bod
y. It
begin
s b
eating a
bout
a m
onth
after
concep
tion a
nd
keep
s g
oin
g
for
a life
tim
e.
A n
atu
ral “p
acem
aker”
in t
he h
eart
’s w
all
pro
duces a
n e
lectr
ical sig
nal th
at
stim
ula
tes e
ach h
eart
beat.
If
this
pacem
aker
malfu
nctions,
the h
eart
may
sto
p b
eating—
an e
vent
calle
d s
ud
den c
ard
iac a
rrest.
Each y
ear
more
than 3
00,0
00
peop
le in t
he U
nited
Sta
tes s
uffer
sud
den c
ard
iac a
rrest.
In o
lder
peop
le,
heart
dis
ease is t
he u
sual
cause.
In t
hose u
nd
er
age 3
5,
an inb
orn
heart
defe
ct
often is t
o b
lam
e.
This
was t
he c
ase w
ith M
att
Nad
er, t
he y
oung m
an s
how
n a
t le
ft.
He w
ent
into
sud
den c
ard
iac a
rrest
while
pla
ying in a
hig
h s
chool fo
otb
all
gam
e.
Matt
’s p
are
nts
, w
ho w
ere
watc
hin
g t
he g
am
e,
rushed
onto
the f
ield
and
sta
rted
card
iop
ulm
onary
resuscitation (C
PR
) on t
heir life
less s
on.
In C
PR
, a p
ers
on
altern
ate
s m
outh
-to-m
outh
resp
iration w
ith c
hest
com
pre
ssio
ns t
hat
keep
the v
ictim
’s b
lood
movi
ng.
If C
PR
is s
tart
ed
within
4 t
o 6
min
ute
s,
the v
ictim
’s c
hances o
f surv
ivin
g t
he a
rrest
rise b
y 50 p
erc
ent.
CP
R d
oes n
ot
resta
rt a
sto
pp
ed
heart
. That
req
uires a
devi
ce c
alle
d a
defib
rilla
tor, w
hic
h d
eliv
ers
a
str
ong e
lectr
ic c
urr
ent
to t
he c
hest.
With luck t
he s
hock q
uic
kly
resta
rts t
he p
acem
aker. In M
att
’s c
ase,
a b
ysta
nd
er
ran t
o g
et
the
school’s
auto
mate
d e
xte
rnal d
efib
rilla
tor
(AE
D). T
his
devi
ce,
ab
out
the s
ize o
f a lap
top
com
pute
r, p
rovi
des s
imp
le v
oic
e instr
uctions
on its
use a
nd
if
need
be g
enera
tes a
shock.
Such a
pro
ced
ure
help
ed
save
Matt
Nad
er.
The p
ub
lic h
ealth v
alu
e o
f A
ED
s n
ow
is w
idely
recogniz
ed
. M
any
schools
, senio
r cente
rs,
shop
pin
g m
alls
, hote
ls,
and
airp
ort
s k
eep
one o
f th
ese life
save
rs o
n h
and
.
In t
his
chap
ter
you w
ill learn
ab
out
the s
tructu
re a
nd
function o
f th
e c
ard
iova
scula
r
sys
tem
—th
e h
eart
and
blo
od
vessels
. S
eve
ral to
pic
s w
ill h
elp
you t
o u
nd
ers
tand
the b
iolo
gy
that
und
erlie
s C
PR
and
the u
se o
f an A
ED
. If y
ou w
ould
lik
e t
o learn
how
to s
ave
liv
es w
ith
these m
eth
od
s,
the A
merican H
eart
Associa
tion,
the A
merican R
ed
Cro
ss,
and
many
oth
er
com
munity
org
aniz
ations p
rovi
de t
rain
ing.
Takin
g t
ime t
o learn
these s
kill is s
om
eth
ing w
e
all
can d
o f
or
one a
noth
er.
121
LINKS TO EARLIER
CONCEPTS
•This chapte
r begins o
ur stu
dy o
f
the b
ody’s m
ajor inte
rnal org
an
syste
ms and how each contribute
s
to homeosta
sis. It looks m
ore
closely
at card
iac m
uscle (4.3) and at th
e
specialized cell junctions in this
tissue (4.6).
•You w
ill see how the tubelike o
rgans
called b
lood vessels are
built from
layers o
f epithelium, connective
tissue, and smooth
muscle (4.1–4.3).
•W
e also consider card
iovascular
diseases and d
isord
ers, including
links b
etw
een heart health and
lipopro
teins and choleste
rol
(2.10, 2.12).
How W
ould You V
ote?
So
me a
dvo
cate
s t
hin
k t
hat
CP
R t
rain
ing
sho
uld
be a
req
uired
min
i-co
urs
e in h
igh s
cho
ols
.
Peo
ple
who
learn
CP
R a
lso
must
be p
erio
dic
ally
recert
ifie
d.
Wo
uld
yo
u f
avo
r m
and
ato
ry C
PR
train
ing
in h
igh s
cho
ols
? S
ee C
eng
ag
eN
OW
fo
r
deta
ils,
then v
ote
onlin
e.
KEYCONCEPTS
Circulating Blood
The card
iovascular syste
m tra
nsports oxygen, nutrients, horm
ones,
and o
ther substa
nces swiftly to b
ody cells. It also carries away
waste
s and cell p
roducts. Section 7.1
Pumping Blood
The heart is a m
uscular pump. Heart contractions p
rovide
the force that drives b
lood thro
ugh the card
iovascular
syste
m’s arteries and veins. Sections 7.2–7.5
Blood Vessels
Various types o
f blood vessels, including arteries, arterioles,
capillaries, venules, and veins, are
specialized for differe
nt
blood tra
nsport functions. Sections 7.6–7.9
Disorders of the Circulatory System and Homeostasis
Sections 7.8–7.10
Circulation: The Heart
and Blood Vessels
7Be Not Still, My Beating Heart!
IMPACTS,
ISSUES
122
CHAPTER 7
The Cardiovascular System: Moving Blood through the Body
7.1
�The cardiovascular system is built to rapidly
transport blood to every living cell in the body.
� Links to Diffusion 3.10, Metabolism 3.13
Figure 7.1Animated!
Th
e h
ea
rt a
nd
blo
od
ve
sse
ls m
ak
e u
p t
he
ca
rdio
va
sc
ula
r syste
m.
Art
eries,
whic
h c
arr
y
oxyg
enate
d b
loo
d t
o t
issues,
are
shad
ed
red
. Vein
s,
whic
h c
arr
y d
eo
xyg
enate
d b
loo
d a
way f
rom
tis
sues,
are
shad
ed
blu
e.
No
tice,
ho
wever, t
hat
for
the p
ulm
onary
art
eries a
nd
vein
s t
he r
ole
s a
re r
evers
ed
.
Carries blood that has
passed through small
intestine and then liver
Jugular Veins
Receive blood from brain
and from tissues of head
Superior Vena Cava
Receives blood from veins
of upper body
Pulmonary Veins
Deliver oxygenated blood
from the lungs to the heart
Hepatic Vein
Renal Vein
Carries processed blood
away from kidneys
Inferior Vena Cava
Receives blood from all
veins below diaphragm
Iliac Veins
Carry blood away from
the pelvic organs and
lower abdominal wall
Femoral Vein
Carries blood away from
the thigh and inner knee
Carotid Arteries
Deliver blood to neck, head, brain
Ascending Aorta
Carries oxygenated blood away
from heart; the largest artery
Pulmonary Arteries
Deliver oxygen-poor blood from
the heart to the lungs
Coronary Arteries
Service the cardiac muscle
cells of heart
Brachial Artery
Delivers blood to upper limbs;
blood pressure measured here
Renal Artery
Delivers blood to kidneys,
where its volume, chemical
make up are adjusted
Abdominal Aorta
Delivers blood to arteries leading
to the digestive tract, kidneys,
pelvic organs, lower limbs
Iliac Arteries
Deliver blood to pelvic organs
and lower abdominal wall
Femoral Artery
Delivers blood to the thigh and
inner knee
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
123
The heart and blood vessels
make up the cardiovascular system
“Car
dio
vas
cula
r” c
om
es f
rom
th
e G
reek
kar
dia
(hea
rt)
and
the
Lat
in v
ascu
lum
(ves
sel)
. A
s y
ou
can
see
in
Fig
ure
7.1
the
ca
rdio
va
sc
ula
r syste
m h
as t
wo
mai
n e
lem
ents
, th
e
hea
rt a
nd
blo
od
ves
sels
.
•T
he
he
art
is a
mu
scu
lar
pu
mp
th
at g
ener
ates
th
e
pre
ssu
re
req
uir
ed
to
mo
ve
blo
od
th
rou
gh
ou
t
the
bo
dy.
•B
loo
d v
esse
ls a
re t
ub
es o
f d
iffe
ren
t d
iam
eter
s th
at
tran
spo
rt b
loo
d.
Th
e h
eart
pu
mp
s b
loo
d i
nto
art
eri
es
, w
hic
h h
ave
a
larg
e d
iam
eter
. F
rom
th
ere
blo
od
flo
ws
into
sm
alle
r an
d
nar
row
er
ves
sels
ca
lled
a
rte
rio
les
, w
hic
h
bra
nch
in
to
even
nar
row
er c
ap
illa
rie
s.
Blo
od
flo
ws
fro
m c
apil
lari
es
into
sm
all
ve
nu
les
, th
en i
nto
lar
ge-
dia
met
er v
ein
sth
at
retu
rn b
loo
d t
o t
he
hea
rt.
As
yo
u w
ill
read
lat
er o
n,
the
vo
lum
e o
f b
loo
d f
low
ing
to a
par
ticu
lar
par
t o
f th
e b
od
y a
nd
th
e ra
te a
t w
hic
h i
t
flo
ws
bo
th
are
adju
stab
le.
Th
is
flex
ibil
ity
p
erm
its
the
card
iov
ascu
lar
syst
em t
o d
eliv
er b
loo
d i
n w
ays
that
su
it
con
dit
ion
s in
dif
fere
nt
par
ts o
f th
e b
od
y. F
or
exam
ple
,
blo
od
flo
ws
rap
idly
th
rou
gh
art
erie
s, b
ut
in c
apil
lari
es i
t
mu
st
flo
w
slo
wly
so
th
at
ther
e is
ti
me
for
sub
stan
ces
mo
vin
g t
o a
nd
fro
m c
ells
to
dif
fuse
in
to a
nd
ou
t o
f ex
tra-
cell
ula
r fl
uid
(F
igu
re 7
.2).
Th
is s
low
flo
w t
akes
pla
ce i
n
ca
pilla
ry b
ed
s,
wh
ere
blo
od
mo
ves
th
rou
gh
vas
t n
um
-
ber
s o
f sl
end
er c
apil
lari
es.
By
div
idin
g u
p t
he
blo
od
flo
w,
the
cap
illa
ries
han
dle
th
e sa
me
tota
l v
olu
me
of
flo
w a
s th
e
larg
e-d
iam
eter
ves
sels
, b
ut
at a
slo
wer
pac
e.
Blood circulation is essential
to maintain homeostasis
Yo
u m
ay h
ear
som
eon
e re
fer
to t
he
card
iov
ascu
lar
syst
em
as
the
“cir
cula
tory
sy
stem
.”
Th
is
nam
e is
ap
t b
ecau
se
blo
od
cir
cula
tes
thro
ug
h t
he
syst
em,
bri
ng
ing
bo
dy
cel
ls
such
ess
enti
als
as o
xy
gen
, n
utr
ien
ts f
rom
fo
od
, an
d s
ecre
-
tio
ns
such
as
ho
rmo
nes
. Cir
cula
tin
g b
loo
d a
lso
tak
es a
way
the
was
tes
pro
du
ced
b
y
ou
r m
etab
oli
sm,
alo
ng
w
ith
exce
ss h
eat.
In
fac
t, c
ells
dep
end
on
blo
od
to
mak
e co
n-
stan
t p
ick
up
s an
d
del
iver
ies
of
an
amaz
ing
ly
div
erse
ran
ge
of
sub
stan
ces,
in
clu
din
g t
ho
se t
hat
mo
ve
into
or
ou
t
of
the
dig
esti
ve
syst
em a
nd
th
e re
spir
ato
ry a
nd
uri
nar
y
syst
ems
(Fig
ure
7.2
).
Ho
meo
stas
is i
s o
ne
of
ou
r co
nst
ant
them
es i
n t
his
bo
ok
,
so i
t’s
go
od
to
kee
p i
n m
ind
th
at m
ain
tain
ing
it
wo
uld
be
imp
oss
ible
wer
e it
no
t fo
r o
ur
circ
ula
tin
g b
loo
d.
Cel
ls
Figure 7.2
To
ge
the
r w
ith
th
e o
the
r syste
ms s
ho
wn
he
re,
the
ca
rdio
va
sc
ula
r syste
m h
elp
s m
ain
tain
fa
vo
rab
le o
pe
rati
ng
co
nd
itio
ns i
n t
he
in
tern
al
en
vir
on
me
nt.
mu
st e
xch
ang
e su
bst
ance
s w
ith
blo
od
bec
ause
th
at i
s a
key
way
cel
ls a
dju
st t
o c
han
ges
in
th
e ch
emic
al m
akeu
p o
f
the
extr
acel
lula
r fl
uid
aro
un
d t
hem
—p
art
of
the
“in
tern
al
env
iro
nm
ent”
in
wh
ich
th
ey l
ive.
The cardiovascular system is linked
to the lymphatic system
Th
e h
eart
’s
pu
mp
ing
a
ctio
n
pu
ts
pre
ssu
re
on
b
loo
d
flo
win
g
thro
ug
h
the
ca
rdio
va
scu
lar
syst
em
. P
art
ly
bec
au
se o
f th
is p
ress
ure
, sm
all
am
ou
nts
of
wa
ter
an
d
som
e p
rote
ins
dis
solv
ed i
n b
loo
d a
re f
orc
ed o
ut
an
d
bec
om
e p
art
of
inte
rsti
tia
l fl
uid
(th
e fl
uid
bet
wee
n c
ells
).
An
el
ab
ora
te
net
wo
rk
of
dra
ina
ge
ves
sels
p
ick
s u
p
exce
ss e
xtr
ace
llu
lar
flu
id a
nd
usa
ble
su
bst
an
ces
in i
t—
such
as
wa
ter
an
d p
rote
ins—
an
d r
etu
rns
them
to
th
e
card
iov
asc
ula
r sy
stem
. Th
is v
esse
l n
etw
ork
is
pa
rt o
f th
e
lym
ph
ati
c sy
stem
, w
hic
h w
e co
nsi
der
in
Ch
ap
ter
9.
Take-Home Message
What
is t
he c
ard
iovascula
r syste
m?
•T
he c
ard
iovascula
r syste
m c
onsis
ts o
f th
e h
eart
and
the b
loo
d
vessels
.
•T
he c
ard
iovacula
r syste
m t
ransp
ort
s s
ub
sta
nces t
o a
nd
fro
m
the f
luid
that
bath
es a
ll liv
ing
cells
.
Urinary
System
Circulatory
System
food, water intake
elimination
of carbon
dioxide
elimination of
excess water,
salts, wastes
water,
solutes
carbon
dioxide
oxygen
nutrients,
water,
salts
elimination
of food
residues
rapid transport
to and from all
living cells
oxygen intake
Respiratory
System
Digestive
System
�In a lifetime of 70 years, the human heart beats
some 2.5 billion times. This durable pump is the
centerpiece of the cardiovascular system.
�Links to Epithelium 4.1, Muscle tissue 4.3
Ro
ug
hly
sp
eak
ing
, y
ou
r h
eart
is
loca
ted
in
th
e ce
nte
r o
f
yo
ur
ches
t (F
igu
re 7
.3a)
. It
s st
ruct
ure
ref
lect
s it
s ro
le a
s a
lon
g-l
asti
ng
pu
mp
. T
he
hea
rt i
s m
ost
ly c
ard
iac
mu
scle
tiss
ue,
th
e m
yo
ca
rdiu
m(F
igu
re 7
.3b)
. A
tou
gh
, fi
bro
us
sac,
th
e p
eric
ard
ium
(pe
ri!
aro
un
d),
su
rro
un
ds,
pro
tect
s,
and
lu
bri
cate
s it
. T
he
hea
rt’s
ch
amb
ers
hav
e a
smo
oth
lin
ing
(en
do
card
ium
) co
mp
ose
d o
f co
nn
ecti
ve
tiss
ue
and
a la
yer
of
epit
hel
ial
cell
s. T
he
epit
hel
ial
cell
lay
er,
kn
ow
n a
s
end
oth
eliu
m,
als
o
lin
es
the
insi
de
of
blo
od
ves
sels
.
The heart has
two halves and
four chambers
Ath
ick
w
all
, th
e s
ep
tum
,
div
ides
th
e h
eart
in
to
two
ha
lves
, ri
gh
t a
nd
le
ft.
Ea
ch
ha
lf
ha
s tw
o
cha
mb
ers:
a
n
atr
ium
(plu
ral:
at
ria)
lo
cate
d
ab
ov
e a
ve
ntr
icle
. F
lap
s o
f
124
CHAPTER 7
The Heart: A Double Pump
7.2
mem
bra
ne
sep
arat
e th
e tw
o c
ham
ber
s an
d s
erv
e as
a o
ne-
way
atr
iove
ntr
icu
lar
va
lve
(AV
val
ve)
bet
wee
n t
hem
. Th
e
AV
val
ve
in t
he
rig
ht
hal
f o
f th
e h
eart
is
call
ed a
tri
cusp
id
valv
eb
ecau
se
its
thre
e fl
aps
com
e to
get
her
in
p
oin
ted
cusp
s (F
igu
re 7
.3c)
. In
th
e h
eart
’s l
eft
hal
f th
e A
V v
alv
e
con
sist
s o
f ju
st t
wo
fla
ps;
it
is c
alle
d t
he
bicu
spid
val
ve o
r
mit
ral
valv
e. T
ou
gh
, co
llag
en-r
ein
forc
ed s
tran
ds
(ch
ord
ae
ten
din
eae,
or
“hea
rtst
rin
gs”
) co
nn
ect
the
AV
val
ve
flap
s to
con
e-sh
aped
mu
scle
s th
at e
xte
nd
ou
t fr
om
th
e v
entr
icle
wa
ll.
Wh
en
a
blo
od
-fil
led
v
entr
icle
co
ntr
act
s,
this
arra
ng
emen
t p
rev
ents
th
e fl
aps
fro
m o
pen
ing
bac
kw
ard
into
th
e at
riu
m.
Eac
h h
alf
of
the
hea
rt a
lso
has
a h
alf-
mo
on
–sh
aped
se
milu
na
r va
lve
bet
wee
n t
he
ven
tric
le a
nd
the
arte
ries
lea
din
g a
way
fro
m i
t. D
uri
ng
a h
eart
bea
t, t
his
val
ve
op
ens
and
clo
ses
in w
ays
that
kee
p b
loo
d m
ov
ing
in
on
e d
irec
tio
n t
hro
ug
h t
he
bo
dy.
Th
e h
eart
h
as
its
ow
n
“co
ron
ary
ci
rcu
lati
on
.”
Tw
o
co
ron
ary
art
eri
es l
ead
in
to a
cap
illa
ry b
ed t
hat
ser
vic
es
mo
st o
f th
e ca
rdia
c m
usc
le (
Fig
ure
7.4
). T
hey
bra
nch
off
the
ao
rta
, th
e m
ajo
r ar
tery
car
ryin
g o
xy
gen
ated
blo
od
away
fro
m t
he
hea
rt.
In a “heartbeat,” the heart’s
chambers contract, then relax
Blo
od
is
p
um
ped
ea
ch
tim
e th
e h
eart
b
eats
. It
ta
kes
less
th
an a
sec
on
d f
or
a “h
eart
bea
t”—
on
e se
qu
ence
of
con
trac
tio
n
and
re
lax
atio
n
of
the
hea
rt
cham
ber
s.
Th
e
seq
uen
ce
occ
urs
al
mo
st
sim
ult
aneo
usl
y
in
bo
th
sid
es
of
the
hea
rt.
Th
e co
ntr
acti
on
p
has
e is
ca
lled
systo
le
( SIS
S-t
oe-
lee)
, an
d t
he
rela
xat
ion
ph
ase
is c
alle
d d
iasto
le
(dy
e-A
SS-t
oe-
lee)
. T
his
se
qu
ence
is
th
e c
ard
iac
c
yc
le
dia
gra
mm
ed i
n F
igu
re 7
.5.
Figure 7.3Animated!
Th
e h
ea
rt i
s d
ivid
ed
in
to r
igh
t a
nd
le
ft h
alv
es.
(a)
Lo
catio
n o
f th
e h
eart
. (b
) C
uta
way v
iew
sho
win
g t
he
heart
’s inte
rnal o
rganiz
atio
n,
and
(c
) valv
es o
f th
e h
eart
. In
this
dra
win
g,
yo
u a
re lo
okin
g d
ow
n a
t th
e h
eart
. T
he a
tria
have b
een r
em
oved
so
that
the a
trio
ventr
icula
r (A
V)
and
sem
ilunar
valv
es a
re v
isib
le.
two
cusps
three
cusps
left
atrioventricular
valve (bicuspid
or mitral valve)
left semilunar
valve (between
left ventricle
and aorta)
right
semilunar
valve (between
right ventricle
and pulmonary
arteries)
right
atrioventricular
valve
(tricuspid)
Front of chest
right lung
diaphragm
heart
left lung
1
2
3
4
5 6 7 8
rib cage
trunk of
pulmonary
arteries
superior vena cava
right semilunar valve
right pulmonary veins
right atrium
right ventricle
right AV valve (opened)
inferior vena cava
septum (partition that divides
the heart into two halves)
muscles that keep valve
from pointing wrong way
aorta
left semilunar
valve
left pulmonar y
veins
left atrium
left
ventricle
left AV
(opened)
endothelium,
connective
tissue
pericardium
myocardium
a bc
Du
rin
g t
he
cycl
e, t
he
ven
tric
les
rela
x b
efo
re t
he
atri
a
con
trac
t, a
nd
th
e v
entr
icle
s co
ntr
act
wh
en t
he
atri
a re
lax
.
Wh
en t
he
rela
xed
atr
ia a
re f
illi
ng
wit
h b
loo
d,
the
flu
id
pre
ssu
re i
nsi
de
them
ris
es a
nd
th
e A
V v
alv
es o
pen
. B
loo
d
flo
ws
into
th
e v
entr
icle
s, w
hic
h a
re 8
0 p
erce
nt
fill
ed b
y t
he
tim
e th
e at
ria
con
trac
t. A
s th
e fi
lled
ven
tric
les
beg
in t
o
con
trac
t,
flu
id
pre
ssu
re
insi
de
them
incr
ease
s, f
orc
ing
th
e A
V
val
ves
sh
ut.
Th
e ri
sin
g p
ress
ure
then
fo
rces
th
e se
mil
un
ar v
alv
es
op
en—
and
blo
od
flo
ws
ou
t o
f
the
hea
rt a
nd
in
to t
he
aort
a an
d
pu
lmo
na
ry
art
ery.
N
ow
th
e
ven
tric
les
rela
x, a
nd
th
e se
mil
u-
nar
val
ves
clo
se.
Fo
r ab
ou
t h
alf
a se
con
d t
he
atri
a an
d v
entr
icle
s
are
a
ll
in
dia
sto
le.
Th
en
the
blo
od
-fil
led
atr
ia c
on
trac
t, a
nd
the
cycl
e re
pea
ts.
Th
e am
ou
nt
of
blo
od
ea
ch
ven
tric
le p
um
ps
in a
min
ute
is
call
ed t
he
ca
rdia
c o
utp
ut.
On
aver
age,
ev
ery
six
ty s
eco
nd
s th
e
card
iac
ou
tpu
t fr
om
eac
h v
en-
tric
le
is
abo
ut
5 li
ters
—n
earl
y
all
the
blo
od
in
th
e b
od
y. T
his
mea
ns
that
in
a y
ear
each
hal
f o
f
yo
ur
hea
rt p
um
ps
at l
east
2.5
mil
lio
n l
iter
s o
f b
loo
d.
Th
at i
s
mo
re t
han
600
,000
gal
lon
s!
Th
e b
loo
d
and
h
eart
m
ov
e-
men
tsd
uri
ng
th
e ca
rdia
c cy
cle
gen
erat
e an
au
dib
le “
lub
-du
p”
sou
nd
m
ad
e b
y
the
forc
efu
l
clo
sin
g o
f th
e h
eart
’s o
ne-
way
val
ves
. A
t ea
ch “
lub
,” t
he
AV
val
ves
ar
e cl
osi
ng
as
th
e tw
o
ven
tric
les
con
tra
ct.
At
each
“du
p,”
th
e se
mil
un
ar v
alv
es a
re
clo
sin
g a
s th
e v
entr
icle
s re
lax
.
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
125
(superior
vena cava)
(inferior vena cava)
right
coronary
artery
cardiac vein
aorta
(left pulmonary
artery)
left coronary
artery
(left pulmonary
veins)
cardiac vein
Heart
sounds
Atria contract,
and fluid pressure
in ventricles rises
sharply.
Ventricles
contract; blood is
pumped into the
pulmonary artery
and the aorta.
Ventricles relax
even as the atria
begin to fill and
start another
cycle.
Fluid pressure in
filling atria opens AV
valves; blood flows
into ventricles.
1
2
3
4
Figure 7.5Animated!
Th
e h
ea
rt b
ea
ts i
n a
se
qu
en
ce
ca
lle
d t
he
ca
rdia
c c
yc
le.
Figure 7.4
Th
e h
ea
rt i
tse
lf i
s s
erv
ed
by c
oro
na
ry a
rte
rie
s a
nd
ve
ins.
The p
ho
tog
rap
h s
ho
ws a
resin
cast
of
these v
essels
.
coronary
artery
Take-Home Message
Ho
w d
oes t
he h
eart
wo
rk a
s a
do
ub
le p
um
p?
•E
ach h
alf o
f th
e h
eart
is d
ivid
ed
into
an a
triu
m a
nd
a v
entr
icle
.
•D
uring
a c
ard
iac c
ycle
, co
ntr
actio
n o
f th
e a
tria
help
s f
ill t
he
ventr
icle
s.
Co
ntr
actio
n o
f th
e v
entr
icle
s p
um
ps b
loo
d o
ut
the h
eart
.
�Each half of the heart pumps blood. The two
side-by-side pumps are the basis of two
cardiovascular circuits through the body,
each with its own set of arteries, arterioles,
capillaries, venules, and veins.
In the pulmonary circuit, blood picks
up oxygen in the lungs
Th
ep
ulm
on
ary
c
irc
uit
, w
hic
h i
s d
iag
ram
med
in
Fig
ure
7.6
aat
rig
ht,
rec
eiv
es b
loo
d f
rom
tis
sues
an
d
circ
ula
tes
it t
hro
ug
h t
he
lun
gs
for
gas
ex
chan
ge.
Th
e
circ
uit
beg
ins
as b
loo
d f
rom
tis
sues
en
ters
th
e ri
gh
t
atri
um
, th
en m
ov
es t
hro
ug
h t
he
AV
val
ve
into
th
e
rig
ht
ven
tric
le.
As
the
ven
tric
le
fill
s,
the
atri
um
con
trac
ts.
Blo
od
ar
riv
ing
in
th
e ri
gh
t v
entr
icle
is
fair
ly l
ow
in
ox
yg
en a
nd
hig
h i
n c
arb
on
dio
xid
e.
Wh
en
the
ven
tric
le
con
tra
cts,
th
e b
loo
d
mo
ves
thro
ug
h
the
rig
ht
sem
ilu
nar
v
alv
e in
to
the
mai
n
pu
lmo
na
ry
art
ery,
th
en
into
th
e ri
gh
ta
nd
left
pu
lmo
nar
y a
rter
ies.
Th
ese
arte
ries
car
ry t
he
blo
od
to
the
two
lu
ng
s,
wh
ere
(in
ca
pil
lari
es)
it
pic
ks
up
ox
yg
en a
nd
giv
es u
p c
arb
on
dio
xid
e th
at w
ill
be
exh
ale
d.
Th
e fr
esh
ly
ox
yg
ena
ted
b
loo
d
retu
rns
thro
ug
h t
wo
set
s o
f p
ulm
on
ary
vei
ns
to t
he
hea
rt’s
left
atr
ium
, co
mp
leti
ng
th
e ci
rcu
it.
In the systemic circuit, blood travels
to and from tissues
In t
he
syste
mic
c
irc
uit
(Fig
ure
7.6
b),
ox
yg
enat
ed
blo
od
pu
mp
ed b
y t
he
left
hal
f o
f th
e h
eart
mo
ves
thro
ug
h t
he
bo
dy
an
d r
etu
rns
to t
he
rig
ht
atri
um
.
Th
is
circ
uit
b
egin
s w
hen
th
e le
ft
atri
um
re
ceiv
es
blo
od
fro
m p
ulm
on
ary
vei
ns,
an
d t
his
blo
od
mo
ves
thro
ug
h a
n A
V (
bic
usp
id)
val
ve
to t
he
left
ven
tric
le.
Th
is c
ham
ber
co
ntr
acts
wit
h g
reat
fo
rce,
sen
din
g
blo
od
co
urs
ing
th
rou
gh
a s
emil
un
ar v
alv
e in
to t
he
aort
a. As
the
aort
a d
esce
nd
s in
to t
he
tors
o (
see
Fig
ure
7.1)
, m
ajo
r ar
teri
es b
ran
ch o
ff i
t, f
un
nel
ing
blo
od
to
org
an
s a
nd
tis
sues
wh
ere
O2
is u
sed
an
d C
O2
is
pro
du
ced
. F
or
exam
ple
, in
a r
esti
ng
per
son
, ea
ch
min
ute
a
fi
fth
o
f th
e b
loo
d
pu
mp
ed
into
th
e
syst
emic
cir
cula
tio
n e
nte
rs t
he
kid
ney
s (F
igu
re 7
.6c)
via
ren
al a
rter
ies.
Deo
xy
gen
ated
blo
od
ret
urn
s to
th
e
rig
ht
hal
f o
f th
e h
eart
, w
her
e it
en
ters
th
e p
ul-
mo
nar
y c
ircu
it.
No
tice
th
at i
n b
oth
th
e p
ulm
on
ary
and
th
e sy
stem
ic
circ
uit
s,
blo
od
tr
avel
s th
rou
gh
arte
ries
, ar
teri
ole
s, c
apil
lari
es,
and
ven
ule
s, f
inal
ly
retu
rnin
g t
o t
he
hea
rt i
n v
ein
s. B
loo
d f
rom
th
e h
ead
,
126
CHAPTER 7
The Two Circuits of Blood Flow
7.3
capillary beds of head
and upper extremities
(to pulmonary
circuit)
(from
pulmonary
circuit)
heart
diaphragm (muscular partition between
thoracic and abdominal cavities)
capillary beds of other
organs in thoracic cavity
capillary bed of liver
capillary beds of intestines
capillary beds of other abdominal
organs and lower extremities
aorta
systemic
circuit
for blood
flow
pulmonary
circuit
for blood
flow
pulmonary
veins
pulmonary
trunk
(to systemic circuit)
right pulmonary artery
left pulmonary artery
capillary
bed of
right
lung
capillary bed
of left lung
heart
(from
systemic
circuit)
hepatic portal vein
A B
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
127
arm
s, a
nd
ch
est
arri
ves
th
rou
gh
th
e su
per
ior
ven
a ca
va.
Th
ein
feri
or v
ena
cav
a co
llec
ts b
loo
d f
rom
th
e lo
wer
par
t o
f
the
bo
dy.
Bec
ause
th
e h
eart
p
um
ps
con
stan
tly,
th
e v
olu
me
of
flo
w t
hro
ug
h t
he
enti
re s
yst
em e
ach
min
ute
is
equ
al t
o t
he
vo
lum
e o
f b
loo
d r
etu
rned
to
th
e h
eart
eac
h m
inu
te.
Blood from the digestive tract is shunted
through the liver for processing
As
yo
u c
an
see
nea
r th
e b
ott
om
of
Fig
ure
7.7
, b
loo
d
pa
ssin
g
thro
ug
h
cap
illa
ry
bed
s in
th
e d
iges
tiv
e tr
act
tra
vel
s to
an
oth
er c
ap
illa
ry b
ed i
n t
he
liv
er. A
fter
a m
eal,
the
he
pa
tic
po
rta
l ve
inb
rin
gs
nu
trie
nt-
lad
en b
loo
d t
o
this
cap
illa
ry b
ed. A
s b
loo
d s
eep
s th
rou
gh
it,
th
e li
ver
can
rem
ov
e im
pu
riti
es
an
d
pro
cess
a
bso
rbed
su
bst
an
ces.
lungs
all other regions
cardiac muscle
bone
skin
brain
skeletal muscle
kidneys
liver
digestive tract
heart’s right half
heart’s left half
10
0%
21
%
6%
20
%
15
%
13
%
9%
5%
3%
8%
C
inferior
vena cava
hepatic vein
liver capillary
beds
stomach
liver
gallbladder
spleen
pancreas
large
intestine
hepatic
portal
vein
large
intestine
(cut away)
small
intestine
Figure 7.6
Animated!
Ea
ch
ha
lf o
f th
e h
ea
rt p
um
ps b
loo
d
in a
dif
fere
nt
cir
cu
it.
The (
a)
pulm
onary
and
(b
) syste
mic
circuits
for
blo
od
flo
w in t
he c
ard
iovascula
r syste
m.
(c)
Dis
trib
utio
n o
f th
e
heart
’s o
utp
ut
in p
eo
ple
nap
pin
g.
Figure 7.7
Blo
od
fro
m t
he
dig
esti
ve
tra
ct
de
tou
rs t
o t
he
liv
er.
Arr
ow
s s
ho
w t
he d
irectio
n in w
hic
h b
loo
d f
low
s.
Th
e v
esse
ls
inv
olv
ed
in
this
d
eto
ur
coll
ecti
vel
y
are
call
ed t
he
hep
atic
por
tal
syst
em(F
igu
re 7
.7).
Yo
u w
ill
rea
d
mo
re a
bo
ut
this
to
pic
in
Ch
ap
ter
11.
Blo
od
le
av
ing
th
e li
ver
’s
cap
illa
ry
bed
en
ters
th
e
gen
era
l ci
rcu
lati
on
th
rou
gh
a
h
epat
ic
vei
n.
Th
e li
ver
rece
ives
ox
yg
ena
ted
blo
od
via
th
e h
epat
ic a
rter
y.
Take-Home Message
What
are
the t
wo
circuits o
f b
loo
d f
low
in t
he b
od
y?
•A
sho
rt p
ulm
onary
circuit c
arr
ies b
loo
d t
hro
ug
h t
he lun
gs f
or
gas e
xchang
e.
A lo
ng
syste
mic
circuit t
ransp
ort
s b
loo
d t
o a
nd
fro
m t
issues.
•A
fter
meals
, th
e b
loo
d in c
ap
illary
bed
s in t
he G
I tr
act
is
div
ert
ed
to
the liv
er
for
pro
cessin
g.
It t
hen r
etu
rns t
o t
he g
enera
l
circula
tio
n.
128
CHAPTER 7
How Cardiac Muscle Contracts
7.4
�Unlike skeletal muscle, which contracts only when
orders arrive from the nervous system, cardiac
muscle contracts—and the heart beats—
spontaneously.
�Link to Muscle tissue 4.3
Electrical signals from “pacemaker” cells
drive the heart’s contractions
Car
dia
c m
usc
le c
ells
bra
nch
, th
en l
ink
to
on
e an
oth
er a
t
thei
r en
din
gs.
Ju
nct
ion
s ca
lled
in
terc
alat
ed d
iscs
sp
an b
oth
pla
sma
mem
bra
nes
of
nei
gh
bo
rin
g c
ells
(F
igu
re 7
.8).
Wit
h
each
hea
rtb
eat,
sig
nal
s ca
llin
g f
or
con
trac
tio
n s
pre
ad s
o
rap
idly
ac
ross
th
e ju
nct
ion
s th
at
card
iac
mu
scle
ce
lls
con
trac
t to
get
her
, al
mo
st a
s if
th
ey w
ere
a si
ng
le u
nit
.
Wh
ere
do
th
e co
ntr
acti
on
sig
nal
s co
me
fro
m?
Ab
ou
t 1
per
cen
t o
f ca
rdia
c m
usc
le c
ells
do
no
t co
ntr
act,
bu
t in
stea
d
fun
ctio
n a
s th
e c
ard
iac
c
on
du
cti
on
syste
m.
So
me
of
thes
e ce
lls
are
self
-ex
citi
ng
“p
acem
aker
” ce
lls—
that
is
,
they
sp
on
tan
eou
sly
g
ener
ate
a
nd
co
nd
uct
el
ectr
ica
l
imp
uls
es.
Th
ose
im
pu
lses
are
th
e si
gn
als
that
sti
mu
late
con
trac
tio
ns
in t
he
hea
rt’s
co
ntr
acti
le c
ells
. B
ecau
se t
he
card
iac
con
du
ctio
n s
yst
em i
s in
dep
end
ent
of
the
ner
vo
us
syst
em,
the
hea
rt w
ill
kee
p r
igh
t o
n b
eati
ng
ev
en i
f al
l
ner
ves
lea
din
g t
o t
he
hea
rt a
re s
ever
ed!
Ex
cita
tio
n b
egin
s w
ith
a c
lust
er o
f ce
lls
in t
he
up
per
wa
ll o
f th
e ri
gh
t a
triu
m (
Fig
ure
7.9
). A
bo
ut
70
tim
es a
min
ute
, th
is s
ino
atr
ial
(SA
) n
od
e g
ener
ate
s w
av
es o
f
exci
tati
on
. E
ach
wa
ve
spre
ad
s sw
iftl
y o
ver
bo
th a
tria
an
d
cau
ses
the
m
to
con
tra
ct.
It
the
n
rea
che
s th
e
atr
iove
ntr
icu
lar
(AV
) n
od
e
in
the
sep
tum
d
ivid
ing
th
e
two
atr
ia.
Wh
en
a st
imu
lus
reac
hes
the
AV
no
de,
it
slo
ws
a li
ttle
,
then
qu
ick
ly c
on
tin
ues
alo
ng
bu
nd
les
of
con
du
ctin
g f
iber
s
that
ex
ten
d t
o e
ach
ven
tric
le.
At
inte
rval
s al
on
g e
ach
bu
n-
dle
, co
nd
uct
ing
ce
lls
call
ed
Pu
rkin
je f
iber
s p
ass
the
sig
nal
on
to
co
ntr
acti
le m
usc
le c
ells
in
each
v
entr
icle
. T
he
slo
w
con
du
ctio
n i
n t
he
AV
no
de
is a
n i
mp
ort
ant
par
t o
f th
is
seq
uen
ce.
It
giv
es
the
atri
a ti
me
to
fin
ish
co
ntr
acti
ng
bef
ore
th
e w
ave
of
exci
tati
on
sp
read
s to
th
e v
entr
icle
s.
Of
all
cell
s o
f th
e ca
rdia
c co
nd
uct
ion
sy
stem
, th
e S
A
no
de
fire
s o
ff i
mp
uls
es a
t th
e h
igh
est
freq
uen
cy a
nd
is
the
firs
t re
gio
n t
o r
esp
on
d i
n e
ach
car
dia
c cy
cle.
It
is c
alle
d t
he
ca
rdia
c p
ac
em
ak
er
bec
ause
its
rh
yth
mic
fir
ing
is
the
bas
is f
or
the
no
rmal
rat
e o
f h
eart
bea
t. P
eop
le w
ho
se S
A
no
de
chro
nic
ally
m
alfu
nct
ion
s m
ay
hav
e an
ar
tifi
cial
pac
emak
er i
mp
lan
ted
to
pro
vid
e a
reg
ula
r st
imu
lus
for
thei
r h
eart
co
ntr
acti
on
s.
The nervous system adjusts heart activity
Th
e n
erv
ou
s sy
stem
in
itia
tes
the
con
trac
tio
n o
f sk
elet
al
mu
scle
, b
ut
it c
an o
nly
adj
ust
the
rate
an
d s
tren
gth
of
car-
dia
c m
usc
le c
on
trac
tio
n.
Sti
mu
lati
on
by
on
e se
t o
f n
erv
es
incr
ease
s th
e fo
rce
and
rat
e o
f h
eart
co
ntr
acti
on
s, w
hil
e
stim
ula
tio
n b
y a
no
ther
set
of
ner
ves
can
slo
w h
eart
act
iv-
ity.
Th
e ce
nte
rs f
or
neu
ral
con
tro
l o
f h
eart
fu
nct
ion
s ar
e in
the
spin
al c
ord
an
d p
arts
of
the
bra
in.
Th
ey a
re d
iscu
ssed
mo
re f
ull
y i
n C
hap
ter
13.
Figure 7.9
Animated!
Th
e
ca
rdia
c c
on
du
cti
on
syste
m.
(left
) R
eco
rdin
g o
f a h
eart
beat.
Lett
ers
ind
icate
thre
e w
aves o
f
ele
ctr
ical activity t
hat
were
caused
by t
he s
pre
ad
of
nerv
e
imp
uls
es a
cro
ss c
ard
iac m
uscle
.
R
PT
SQ
junction
between
cells
intercalated disc
Figure 7.8
Inte
rca
late
d d
isc
s
form
co
mm
un
ica
tio
n j
un
cti
on
s
be
twe
en
ca
rdia
c m
usc
le c
ells.
Sig
nals
tra
vel ra
pid
ly a
cro
ss t
he
junctio
ns a
nd
cause c
ells
to
co
ntr
act
nearly in u
nis
on.
SA node
(cardiac pacemaker)
AVnode
bundle of conducting
muscle fibers
Purkinje fibers
contractile heart
muscle cells
Take-Home Message
What
is t
he c
ard
iac p
acem
aker
and
ho
w d
oes it
set
the h
eart
beat?
•T
he S
A n
od
e is t
he c
ard
iac p
acem
aker—
it e
sta
blis
hes a
reg
ula
r
heart
beat.
Its
sp
onta
neo
us,
rep
eate
d e
xcitatio
n s
ignals
sp
read
alo
ng
a s
yste
m o
f m
uscle
cells
that
stim
ula
te a
rhyth
mic
cycle
of
co
ntr
actio
n in t
he h
eart
’s a
tria
, th
en t
he v
entr
icle
s.
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
129
� Heart contractions generate blood pressure, which
changes as blood moves through the cardiovascular
system.
Blood exerts pressure against the walls
of blood vessels
Blo
od
p
ressu
reis
th
e fl
uid
pre
ssu
re t
hat
blo
od
ex
erts
agai
nst
ves
sel
wal
ls. B
loo
d p
ress
ure
is
hig
hes
t in
th
e ao
rta;
then
it
dro
ps
alo
ng
th
e sy
stem
ic c
ircu
it.
Th
e p
ress
ure
ty
p-
ical
ly i
s m
easu
red
wh
en a
per
son
is
at r
est
(Fig
ure
7.1
0).
Fo
r a
n
ad
ult
, th
e N
ati
on
al
Hea
rt,
Lu
ng
, a
nd
B
loo
d
Inst
itu
te
has
es
tab
lish
ed
blo
od
p
ress
ure
v
alu
es
un
der
120/
80
as
the
hea
lth
iest
(T
able
7.
1).
Th
e fi
rst
nu
mb
er,
syst
olic
pre
ssu
re,
is t
he
pea
k o
f p
ress
ure
in
th
e ao
rta
wh
ile
the
left
v
entr
icle
co
ntr
acts
an
d
pu
shes
b
loo
d
into
th
e
aort
a. T
he
seco
nd
nu
mb
er,
dias
toli
c pr
essu
re,
mea
sure
s th
e
low
est
blo
od
pre
ssu
re i
n t
he
aort
a, w
hen
blo
od
is
flo
win
g
ou
t o
f it
an
d t
he
hea
rt i
s re
lax
ed.
Va
lues
fo
r sy
sto
lic
an
d
dia
sto
lic
pre
ssu
re
pro
vid
e
imp
ort
ant
hea
lth
in
form
atio
n.
Ch
ron
ical
ly e
lev
ated
blo
od
pre
ssu
re,
or
hype
rten
sion
, ca
n b
e as
soci
ated
wit
h a
var
iety
of
ills
, su
ch a
s at
her
osc
lero
sis
(Sec
tio
n 7
.8).
Th
e ch
art
in
Fig
ure
7.1
1 li
sts
som
e o
f th
e m
ajo
r ca
use
s an
d r
isk
fac
tors
.
Hy
per
ten
sio
n i
s a
“sil
ent
kil
ler”
th
at c
an l
ead
to
a s
tro
ke
or
hea
rt a
ttac
k. E
ach
yea
r it
kil
ls a
bo
ut
180,
000
Am
eric
ans,
man
y o
f w
ho
m m
ay n
ot
hav
e h
ad a
ny
ou
twar
d s
ym
p-
tom
s. R
ou
gh
ly 4
0 m
illi
on
peo
ple
in
th
e U
nit
ed S
tate
s ar
e
un
awar
e th
at t
hey
hav
e h
yp
erte
nsi
on
.
Hyp
oten
sion
is
abn
orm
ally
lo
wb
loo
d
pre
ssu
re.
Th
is
con
dit
ion
can
dev
elo
p w
hen
fo
r so
me
reas
on
th
ere
is n
ot
eno
ug
h w
ater
in
blo
od
pla
sma—
for
inst
ance
, if
th
ere
are
no
t en
ou
gh
pro
tein
s in
th
e b
loo
d t
o “
pu
ll”
wat
er i
n b
y
osm
osi
s. A
larg
e b
loo
d l
oss
als
o c
an
ca
use
blo
od
pre
ssu
re
to
plu
mm
et.
Su
ch
a d
rast
ic
dec
reas
e is
o
ne
sig
n
of
a
dan
ger
ou
s co
nd
itio
n c
alle
d c
ircu
lato
ry s
hock
.
Figure 7.10Animated!
Me
asu
rin
g b
loo
d p
ressu
re i
s o
ne
wa
y t
o m
on
ito
r c
ard
iova
sc
ula
r h
ea
lth
. A
ho
llow
cuff
att
ached
to
a p
ressure
gaug
e is w
rap
ped
aro
und
the u
pp
er
arm
. T
he c
uff
is
inflate
d t
o a
pre
ssure
ab
ove t
he h
ighest
pre
ssure
of
the c
ard
iac
cycle
—at
systo
le,
when v
entr
icle
s c
ontr
act.
Ab
ove t
his
pre
ssure
,
yo
u c
an’t
hear
so
und
s t
hro
ug
h a
ste
tho
sco
pe p
ositio
ned
belo
w
the c
uff
and
ab
ove t
he b
rachia
l art
ery
, b
ecause n
o b
loo
d is f
low
ing
thro
ug
h t
he v
essel. A
s a
ir in t
he c
uff
is s
low
ly r
ele
ased
, so
me
blo
od
flo
ws into
the a
rtery
. T
he t
urb
ule
nt
flo
w c
auses s
oft
tap
pin
g
so
und
s.
When t
he t
ap
pin
g s
tart
s,
the g
aug
e’s
valu
e is t
he s
ysto
lic
pre
ssure
, m
easure
d in m
illim
ete
rs o
f m
erc
ury
(H
g). T
his
valu
e
measure
s h
ow
far
the p
ressure
wo
uld
fo
rce m
erc
ury
to
mo
ve
up
ward
in a
narr
ow
gla
ss c
olu
mn.
Mo
re a
ir is r
ele
ased
fro
m t
he c
uff
. Just
aft
er
the s
ound
s g
row
dull
and
muff
led
, b
loo
d is f
low
ing
ste
ad
ily,
so
the t
urb
ule
nce a
nd
tap
pin
g e
nd
. T
he s
ilence c
orr
esp
ond
s t
o d
iasto
lic p
ressure
at
the
end
of
a c
ard
iac c
ycle
, b
efo
re t
he h
eart
pum
ps o
ut
blo
od
. A
desirab
le r
ead
ing
is u
nd
er
80 m
m H
g.
Figure 7.11
A v
ari
ety
of
fac
tors
ma
y c
au
se
hyp
ert
en
sio
n.
Blood Pressure
7.5
Take-Home Message
What
is b
loo
d p
ressure
?
•H
eart
co
ntr
actio
ns g
enera
te b
loo
d p
ressure
. S
ysto
lic p
ressure
is
the p
eak o
f p
ressure
in t
he a
ort
a w
hile
blo
od
pum
ped
by t
he left
ventr
icle
is f
low
ing
into
it.
Dia
sto
lic p
ressure
measure
s t
he lo
west
blo
od
pre
ssure
in t
he a
ort
a,
when b
loo
d is f
low
ing
out
of
it.
Systo
lic
Dia
sto
lic
Normal
10
0–1
19
60
–7
9
Hypotension
Less t
han
10
0L
ess t
han
60
Prehypertension
12
0–1
39
80
–1
39
Hypertension
14
0 a
nd
up
90
an
d u
p
TABLE 7.1Blood Pressure Values (mm of Hg)
1.
Sm
okin
g
2.
Ob
esit
y
3.
Sed
en
tary
lifesty
le
4.
Ch
ron
ic s
tress
5.
A d
iet
low
in
fru
its,
veg
eta
ble
s,
dair
y
foo
ds,
an
d o
ther
so
urc
es o
f p
ota
ssiu
m
an
d c
alc
ium
6.
Excessiv
e s
alt
in
take (
in s
om
e in
div
idu
als
)
7.
Po
or
salt
man
ag
em
en
t b
y t
he k
idn
eys,
usu
ally
du
e t
o d
isease
Risk Factors for Hypertension
130
CHAPTER 7
Structure and Functions of Blood Vessels
7.6
�As with all body parts, structure is key to the
functions of blood vessels. All the vessels transport
blood, but there are important differences in how
different kinds manage blood flow and blood
pressure.
�Links to Epithelium 4.1, Connective tissues 4.2
Arteries are large blood pipelines
Th
e w
all
of
an a
rter
y h
as s
ever
al t
issu
e la
yer
s (F
igu
re
7.12
a).
Th
e o
ute
r la
yer
is
mai
nly
co
llag
en,
wh
ich
an
cho
rs
the
ves
sel
to t
he
tiss
ue
it r
un
s th
rou
gh
. A
thic
k m
idd
le
lay
er o
f sm
oo
th m
usc
le i
s sa
nd
wic
hed
bet
wee
n t
hin
ner
lay
ers
con
tain
ing
ela
stin
. T
he
inn
erm
ost
lay
er i
s a
thin
shee
t o
f en
do
thel
ium
. T
og
eth
er t
hes
e la
yer
s fo
rm a
th
ick
,
mu
scu
lar,
a
nd
el
ast
ic
wa
ll.
In
a
larg
e a
rter
y
the
wa
ll
bu
lges
sli
gh
tly
un
der
th
e p
ress
ure
su
rge
cau
sed
wh
en a
ven
tric
le c
on
trac
ts.
In a
rter
ies
nea
r th
e b
od
y s
urf
ace,
as
in
the
wri
st,
yo
u c
an f
eel
the
surg
es a
s y
ou
r p
uls
e.
Th
e b
ulg
ing
of
arte
ry w
alls
hel
ps
kee
p b
loo
d f
low
ing
on
th
rou
gh
th
e sy
stem
. H
ow
? F
or
a m
om
ent,
so
me
of
the
blo
od
pu
mp
ed d
uri
ng
th
e sy
sto
le p
has
e o
f ea
ch c
ard
iac
cycl
e is
sto
red
in
th
e “b
ulg
e”; t
he
elas
tic
reco
il o
f th
e ar
tery
then
fo
rces
th
at
sto
red
b
loo
d
on
war
d
du
rin
gd
iast
ole
,
wh
en h
eart
ch
am
ber
s a
re r
ela
xed
. In
ad
dit
ion
to
str
etch
-
ab
le w
all
s, a
rter
ies
als
o h
av
e la
rge
dia
met
ers.
Fo
r th
is
rea
son
, th
ey p
rese
nt
litt
le r
esis
tan
ce t
o b
loo
d f
low
, so
blo
od
pre
ssu
re d
oes
no
t d
rop
mu
ch i
n t
he
larg
e a
rter
ies
of
the
syst
emic
an
d p
ulm
on
ary
cir
cuit
s (F
igu
re 7
.13
).
Arterioles are control points
for blood flow
Art
erie
s b
ran
ch i
nto
nar
row
er a
rter
iole
s, w
hic
h h
ave
a
wal
l b
uil
t o
f ri
ng
s o
f sm
oo
th m
usc
le o
ver
a s
ing
le l
ayer
of
elas
tic
fib
ers
(Fig
ure
7.1
2b).
Bec
ause
th
ey a
re b
uil
t th
is
way
, ar
teri
ole
s ca
n d
ilat
e (e
nla
rge
in d
iam
eter
) w
hen
th
e
smo
oth
mu
scle
rel
ax
es o
r co
nst
rict
(sh
rin
k i
n d
iam
eter
)
wh
en t
he
smo
oth
mu
scle
co
ntr
act
s. A
rter
iole
s o
ffer
mo
re
resi
stan
ce t
o b
loo
d f
low
th
an o
ther
ves
sels
do
. A
s th
e
blo
od
flo
w s
low
s, i
t ca
n b
e co
ntr
oll
ed i
n w
ays
that
ad
just
ho
w m
uch
of
the
tota
l v
olu
me
go
es t
o d
iffe
ren
t b
od
y
reg
ion
s. F
or
exam
ple
, y
ou
bec
om
e d
row
sy a
fter
a l
arg
e
mea
l in
par
t b
ecau
se c
on
tro
l si
gn
als
div
ert
blo
od
aw
ay
fro
m y
ou
r b
rain
in
fav
or
of
yo
ur
dig
esti
ve
syst
em.
Capillaries are specialized for diffusion
Yo
ur
bo
dy
has
ab
ou
t 2
mil
es o
f ar
teri
es a
nd
vei
ns
bu
t a
wh
op
pin
g 6
2,00
0 m
iles
of
cap
illa
ries
. Eac
h c
apil
lary
bed
is
wh
ere
sub
stan
ces
can
dif
fuse
bet
wee
n b
loo
d a
nd
tis
sue
flu
id.
Th
is i
s tr
uly
wh
ere
“th
e ru
bb
er m
eets
th
e ro
ad”
wh
en i
t co
mes
to
ex
cha
ng
es o
f g
ase
s (o
xy
gen
an
d c
arb
on
dio
xid
e),
nu
trie
nts
, an
d w
aste
s. A
s b
efit
s it
s fu
nct
ion
in
dif
fusi
on
, a
cap
illa
ry h
as t
he
thin
nes
t w
all
of
any
blo
od
ves
sel—
a si
ng
le l
ayer
of
flat
en
do
thel
ium
(F
igu
re 7
.12c
).
Figure 7.12Animated!
Th
e s
tru
ctu
re o
f a
blo
od
ve
sse
l
ma
tch
es i
ts f
un
cti
on
.
Figure 7.13
Blo
od
pre
ssu
re c
ha
ng
es a
s b
loo
d f
low
s t
hro
ug
h
dif
fere
nt
pa
rts o
f th
e c
ard
iova
sc
ula
r syste
m.
connective
tissue coat
smooth
muscle
endothelium
elastic tissue
elastic tissue
A Artery
endothelium
C Capillary
smooth muscle rings
over elastic tissue
endothelium
B Arteriole
connective
tissue coat
smooth
muscle
endothelium
D Venule
connective
tissue coat
smooth muscle,
elastic fibers
endothelium
valve
E Vein
120
80
40 0
Blood pressure (mm Hg)
(systolic)
(diastolic)
arteries
capillaries
venules
veins
arterioles
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
131
Blo
od
ca
n’t
mo
ve
ver
y f
ast
in
ca
pil
lari
es.
Ho
wev
er,
bec
au
se t
hey
are
so
ex
ten
siv
e, c
ap
illa
ry b
eds
pre
sen
t le
ss
tota
l re
sist
an
ce t
o f
low
th
an
do
th
e a
rter
iole
s le
ad
ing
in
to
them
, so
ov
era
ll b
loo
d p
ress
ure
dro
ps
mo
re s
low
ly i
n
them
. W
e’ll
lo
ok
mo
re c
lose
ly a
t h
ow
ca
pil
lari
es f
un
ctio
n
in t
he
nex
t se
ctio
n.
Venules and veins return blood
to the heart
Ca
pil
lari
es m
erg
e in
to v
enu
les,
or
“li
ttle
vei
ns,
” w
hic
h i
n
turn
mer
ge
into
lar
ge-
dia
met
er v
ein
s. V
enu
les
fun
ctio
n a
litt
le l
ike
cap
illa
ries
, in
th
at s
om
e so
lute
s d
iffu
se a
cro
ss
thei
r re
lati
vel
y t
hin
wal
ls (
Fig
ure
7.1
2d).
Vei
ns
are
la
rge-
dia
met
er,
low
-res
ista
nce
tr
an
spo
rt
tub
es
to
the
hea
rt
(Fig
ure
7.
12e)
. T
hei
r v
alv
es
pre
ven
t
bac
kfl
ow
. W
hen
blo
od
sta
rts
mo
vin
g b
ack
war
d d
ue
to
gra
vit
y, i
t p
ush
es t
he
val
ves
clo
sed
. T
he
vei
n w
all
can
bu
lge
gre
atly
un
der
pre
ssu
re,
mo
re s
o t
han
an
art
eria
l
wal
l. T
hu
s v
ein
s ar
e re
serv
oir
s fo
r v
aria
ble
vo
lum
es o
f
blo
od
. T
og
eth
er,
the
vei
ns
of
an a
du
lt c
an h
old
up
to
50
to
60 p
erce
nt
of
the
tota
l b
loo
d v
olu
me.
Wh
en b
loo
d m
ust
cir
cula
te f
ast
er (
as
du
rin
g e
xer
cise
),
the
smo
oth
mu
scle
in
vei
ns
con
trac
ts.
Th
e w
all
stif
fen
s,
the
vei
n b
ulg
es l
ess,
an
d v
eno
us
pre
ssu
re r
ises
—so
mo
re
blo
od
flo
ws
to t
he
hea
rt (
Fig
ure
7.1
4).
Ven
ou
s p
ress
ure
also
ris
es w
hen
co
ntr
acti
ng
sk
elet
al m
usc
le—
esp
ecia
lly
in
the
leg
s an
d
abd
om
en—
bu
lges
ag
ain
st
adja
cen
t v
ein
s.
Th
is
mu
scle
ac
tiv
ity
h
elp
s re
turn
b
loo
d
thro
ug
h
the
ven
ou
s sy
stem
.
Ob
esit
y,
pre
gn
ancy
, an
d
oth
er
fact
ors
ca
n
wea
ken
ven
ou
s v
alv
es.
Th
e w
alls
of
a va
rico
se v
ein
hav
e b
eco
me
ov
erst
retc
hed
b
eca
use
, o
ver
ti
me,
w
eak
v
alv
es
ha
ve
allo
wed
blo
od
to
po
ol
ther
e.
Vessels help control blood pressure
So
me
arte
ries
, al
l ar
teri
ole
s, a
nd
ev
en v
ein
s h
ave
role
s in
ho
meo
stat
ic
mec
han
ism
s th
at
hel
p
mai
nta
in
adeq
uat
e
blo
od
pre
ssu
re o
ver
tim
e. C
ente
rs i
n t
he
bra
in’s
med
ull
a
mo
nit
or
rest
ing
b
loo
d
pre
ssu
re.
Wh
en
blo
od
p
ress
ure
rise
s ab
no
rmal
ly, t
hey
ord
er t
he
hea
rt t
o c
on
trac
t le
ss o
ften
and
les
s fo
rcef
ull
y. T
hey
als
o o
rder
sm
oo
th m
usc
le i
n a
rte-
rio
les
to r
elax
. Th
e re
sult
is
va
so
dila
tio
n—
an e
nla
rgem
ent
(dil
atio
n)
of
the
ves
sel
dia
met
er. O
n t
he
oth
er h
and
, wh
en
the
cen
ters
det
ect
an a
bn
orm
al d
ecre
ase
in b
loo
d p
ress
ure
,
they
co
mm
and
th
e h
eart
to
bea
t fa
ster
an
d c
on
trac
t m
ore
forc
efu
lly.
Neu
ral
sig
nal
s al
so c
ause
th
e sm
oo
th m
usc
le o
f
arte
rio
les
to c
on
trac
t. T
he
resu
lt i
s va
so
co
nstr
icti
on
, a
nar
row
ing
of
the
ves
sel
dia
met
er.
In s
om
e p
arts
of
the
bo
dy
art
erio
les
hav
e re
cep
tors
fo
r h
orm
on
es t
hat
tri
gg
er
vas
oco
nst
rict
ion
or
vas
od
ilat
ion
, th
us
hel
pin
g t
o m
ain
tain
blo
od
pre
ssu
re.
Rec
all
that
th
e n
erv
ou
s an
d e
nd
ocr
ine
syst
ems
also
con
tro
l h
ow
blo
od
is
allo
cate
d t
o d
iffe
ren
t b
od
y r
egio
ns
at
dif
fere
nt
tim
es. I
n a
dd
itio
n, c
on
dit
ion
s in
a p
arti
cula
r p
art
of
the
bo
dy
can
alt
er b
loo
d f
low
th
ere.
Fo
r in
stan
ce,
wh
en
yo
u r
un
, th
e am
ou
nt
of
ox
yg
en i
n y
ou
r sk
elet
al m
usc
le t
is-
sue
fall
s, w
hil
e le
vel
s o
f ca
rbo
n d
iox
ide,
hy
dro
gen
io
ns,
po
tass
ium
io
ns,
an
d o
ther
su
bst
ance
s ri
se. T
hes
e ch
emic
al
chan
ges
cau
se t
he
smo
oth
mu
scle
in
art
erio
les
to r
elax
.
Th
e v
aso
dil
atio
n r
esu
lts
in m
ore
blo
od
flo
win
g p
ast
the
acti
ve
mu
scle
s. A
t th
e sa
me
tim
e, a
rter
iole
s in
yo
ur
dig
es-
tiv
e tr
act
and
kid
ney
s co
nst
rict
.
Ab
aro
rec
ep
tor
refl
ex h
elp
s p
rov
ide
sho
rt-t
erm
co
n-
tro
l o
ver
blo
od
pre
ssu
re. B
aro
rece
pto
rs a
re p
ress
ure
rec
ep-
tors
in
th
e c
aro
tid
art
eri
es i
n t
he
nec
k,
in t
he
arch
of
the
aort
a, a
nd
els
ewh
ere.
Th
ey m
on
ito
r ch
ang
es i
n m
ean
art
e-
rial
pre
ssu
re (
“mea
n”
!th
e m
idp
oin
t) a
nd
sen
d s
ign
als
to
cen
ters
in
th
e b
rain
. As
des
crib
ed i
n C
hap
ter
13, t
his
in
for-
mat
ion
is
u
sed
to
co
ord
inat
e th
e ra
te
and
st
ren
gth
o
f
hea
rtb
eats
wit
h c
han
ges
in
th
e d
iam
eter
of
arte
rio
les
and
vei
ns.
Th
e b
aro
rece
pto
r re
flex
hel
ps
kee
p b
loo
d p
ress
ure
wit
hin
no
rmal
lim
its
in t
he
face
of
sud
den
ch
an
ges
—su
ch
as
wh
en y
ou
lea
p u
p f
rom
a c
hai
r.
Figure 7.14Animated!
Co
ntr
ac
tin
g s
ke
leta
l
mu
sc
les c
an
in
cre
ase
flu
id p
ressu
re in
a
ve
in.
(a) Valv
es in
med
ium
-siz
ed
vein
s
pre
vent
backflo
w o
f
blo
od
. (b
) S
kele
tal
muscle
s n
ext
to t
he v
ein
co
ntr
act,
help
ing
blo
od
flo
w f
orw
ard
. (c
) S
kele
tal
muscle
s r
ela
x a
nd
valv
es
in t
he v
ein
shut—
pre
venting
backflo
w.
blood flow to heart
valve
open
valve
closed
valve
closed
valve
closed
venous valve
AB
C
Take-Home Message
What
are
the d
iffe
rent
typ
es o
f b
loo
d v
essels
?
•A
rteries a
re t
he m
ain
pip
elin
es f
or
oxyg
enate
d b
loo
d.
Because
art
erio
les c
an d
ilate
and
co
nstr
ict,
they a
re c
ontr
ol p
oin
ts f
or
blo
od
flo
w (
and
pre
ssure
).
• C
ap
illary
bed
s a
re d
iffu
sio
n z
ones.
Blo
od
mo
ves b
ack t
o t
he
heart
thro
ug
h v
enule
s a
nd
vein
s.
Valv
es in v
ein
s p
revent
the
backflo
w o
f b
loo
d d
ue t
o g
ravity.
132
CHAPTER 7
Capillaries: Where Blood Exchanges Substances with Tissues
7.7
�Blood enters the systemic circulation moving swiftly
in the aorta, but this speed has to slow in order for
substances to move into and out of the bloodstream.
�Link to Diffusion 3.10
A vast network of capillaries brings blood
close to nearly all body cells
Yo
ur
bo
dy
co
mes
eq
uip
ped
w
ith
o
ne
ao
rta
, a
fe
w
hu
nd
red
bra
nch
ing
art
erie
s a
nd
vei
ns,
mo
re t
ha
n h
alf
a
mil
lio
n
art
erio
les
an
d
ven
ule
s—a
nd
a
s m
an
y
as
40
bil
lio
n c
ap
illa
ries
! C
ap
illa
ries
are
so
th
in t
ha
t it
wo
uld
tak
e 1
00
of
them
to
eq
ua
l th
e th
ick
nes
s o
f a
hu
ma
n h
air
.
An
d a
t le
ast
on
e o
f th
ese
tin
y v
esse
ls i
s n
ext
to l
ivin
g
cell
s in
nea
rly
all
bo
dy
tis
sues
.
In
ad
dit
ion
to
fo
rmin
g
a
va
st
net
wo
rk
of
ves
sels
(Fig
ure
7
.15
a),
this
b
ran
chin
g
syst
em
als
o
aff
ects
th
e
spee
d a
t w
hic
h b
loo
d f
low
s th
rou
gh
it.
Th
e fl
ow
is
fast
est
in t
he
ao
rta
, qu
ick
ly “
lose
s st
eam
” i
n t
he
mo
re n
um
ero
us
art
erio
les,
an
d s
low
s to
a r
ela
tiv
e cr
aw
l in
th
e n
arr
ow
cap
illa
ries
. T
he
flo
w o
f b
loo
d s
pee
ds
up
ag
ain
as
blo
od
mo
ves
in
to v
ein
s fo
r th
e re
turn
tri
p t
o t
he
hea
rt.
Many substances enter and leave
capillaries by diffusion
Wh
y d
o w
e h
av
e su
ch a
n e
xte
nsi
ve
syst
em o
f ca
pil
lari
es
in w
hic
h b
loo
d s
low
s to
a s
na
il’s
pa
ce?
Rem
emb
er f
rom
Sec
tio
n 7
.6 t
ha
t ca
pil
lari
es a
re w
her
e a
ll t
he
sub
sta
nce
s
tha
t en
ter
an
d l
eav
e ce
lls
are
ex
cha
ng
ed w
ith
th
e b
loo
d,
ma
ny
o
f th
em
by
d
iffu
sio
n.
Bu
t d
iffu
sio
n
is
a
slo
w
pro
cess
th
at
is
no
t ef
fici
ent
ov
er
lon
g
dis
tan
ces.
In
a
larg
e, m
ult
icel
lula
r o
rga
nis
m s
uch
as
a h
um
an
, h
av
ing
bil
lio
ns
of
na
rro
w c
ap
illa
ries
so
lves
bo
th t
hes
e p
rob
lem
s.
Th
ere
is a
ca
pil
lary
ver
y c
lose
to
nea
rly
ev
ery
cel
l, a
nd
in
each
on
e th
e b
loo
d i
s b
are
ly m
ov
ing
. A
s b
loo
d “
cree
ps”
alo
ng
in
ca
pil
lari
es,
ther
e is
ti
me
for
the
nec
essa
ry
exch
an
ges
of
flu
id a
nd
so
lute
s to
ta
ke
pla
ce. I
n f
act
, mo
st
solu
tes,
in
clu
din
g m
ole
cule
s o
f o
xy
gen
an
d c
arb
on
dio
x-
ide,
dif
fuse
acr
oss
th
e ca
pil
lary
wa
ll.
Some substances pass through
“pores” in capillary walls
So
me
sub
sta
nce
s en
ter
an
d l
eav
e ca
pil
lari
es b
y w
ay
of
slit
lik
e a
rea
s b
etw
een
th
e ce
lls
of
cap
illa
ry w
all
s (F
igu
re
7.1
5c)
. T
hes
e “
po
res”
a
re
fill
ed
wit
h
wa
ter.
T
hey
a
re
pa
ssa
ges
fo
r su
bst
an
ces
tha
t ca
nn
ot
dif
fuse
th
rou
gh
th
e
lip
id b
ila
yer
of
the
cell
s th
at
ma
ke
up
th
e ca
pil
lary
wa
ll,
bu
t th
at
can
dis
solv
e in
wa
ter.
Figure 7.15
Ca
pilla
rie
s d
elive
r b
loo
d c
lose
to
ce
lls.
(a)
A r
esin
cast
sho
win
g a
dense n
etw
ork
of
cap
illaries.
(b)
Red
blo
od
cells
mo
vin
g s
ing
le f
ile in c
ap
illaries.
(c)
Ho
w s
ub
sta
nces p
ass t
hro
ug
h
slit
like p
ore
s in t
he w
all
of
a c
ap
illary
.
pores
cell of
capillary wall
a b c
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
133
blood
from
arteriole
outward-directed
bulk flow
cells of
tissue
blood to
venule
inward-directed
osmotic movement
Wh
en t
he
blo
od
pre
ssu
re i
nsi
de
a ca
pil
lary
is
gre
ater
than
pre
ssu
re f
rom
th
e ex
trac
ellu
lar
flu
id o
uts
ide,
wat
er
and
so
lute
s m
ay b
e fo
rced
ou
t o
f th
e v
esse
l—a
typ
e o
f
flu
id m
ov
emen
t ca
lled
“b
ulk
flo
w”
(F
igu
re 7
.16
). V
ari
ou
s
fact
ors
aff
ect
this
pro
cess
, b
ut
on
bal
ance
, a
litt
le m
ore
wa
ter
lea
ves
ca
pil
lari
es t
ha
n e
nte
rs t
hem
. T
he
lym
ph
ati
c
syst
em,
wh
ich
co
nsi
sts
of
lym
ph
ves
sels
, ly
mp
h n
od
es,
and
so
me
oth
er o
rgan
s, r
etu
rns
the
flu
id t
o t
he
blo
od
. Th
is
syst
em a
lso
pla
ys
a m
ajo
r ro
le i
n b
od
y d
efen
se,
and
yo
u
wil
l le
arn
mo
re a
bo
ut
it i
n C
hap
ter
9.
Ov
eral
l, t
he
mo
vem
ents
of
flu
id a
nd
so
lute
s in
to a
nd
ou
t o
f ca
pil
lari
es h
elp
mai
nta
in b
loo
d p
ress
ure
by
ad
din
g
wat
er t
o,
or
sub
trac
tin
g i
t fr
om
, b
loo
d p
lasm
a. T
he
flu
id
tra
ffic
a
lso
h
elp
s m
ain
tain
th
e p
rop
er
flu
id
ba
lan
ce
bet
wee
n b
loo
d a
nd
su
rro
un
din
g t
issu
es.
Blood in capillaries flows
onward to venules
Cap
illa
ry b
eds
are
the
“tu
rnar
ou
nd
po
ints
” fo
r b
loo
d i
n
the
card
iov
ascu
lar
syst
em.
Th
ey r
ecei
ve
blo
od
fro
m a
rte-
rio
les,
a
nd
a
fter
th
e b
loo
d
flo
ws
thro
ug
h
the
bed
it
ente
rs
cha
nn
els
tha
t co
nv
erg
e in
to
ven
ule
s—th
e
beg
inn
ing
of
its
retu
rn t
rip
to
th
e h
eart
(F
igu
re 7
.17)
.
At
the
po
int
wh
ere
a ca
pil
lary
b
ran
ches
in
to
the
cap
illa
ry
bed
, a
wis
py
ri
ng
o
f sm
oo
th
mu
scle
w
rap
s
aro
un
d
it.
Th
is
stru
ctu
re,
a
pre
ca
pilla
ry
sp
hin
cte
r,
reg
ula
tes
the
flo
w o
f b
loo
d i
nto
th
e ca
pil
lary
. Th
e sm
oo
th
mu
scle
is
sen
siti
ve
to c
hem
ica
l ch
an
ges
in
th
e ca
pil
lary
bed
. It
ca
n c
on
tra
ct a
nd
pre
ven
t b
loo
d f
rom
en
teri
ng
th
e
cap
illa
ry,
or
it c
an
rel
ax
an
d l
et b
loo
d f
low
in
.
Figure 7.16Animated!
Flu
id m
ay m
ove
by “
bu
lk f
low
” in
to
an
d o
ut
of
a c
ap
illa
ry b
ed
.
arteriole
smooth muscle
precapillary
sphincter
capillary
venule
Figure 7.17
Th
is d
iag
ram
sh
ow
s t
he
ge
ne
ral
dir
ec
tio
n o
f
blo
od
flo
w t
hro
ug
h a
ca
pilla
ry b
ed
. A
pre
cap
illary
sp
hin
cte
r
wra
ps a
round
the b
ase o
f each c
ap
illary
.
Fo
r ex
amp
le, i
f y
ou
sit
qu
ietl
y a
nd
lis
ten
to
mu
sic,
on
ly
abo
ut
on
e-te
nth
of
the
cap
illa
ries
in
yo
ur
skel
etal
mu
scle
s
are
op
en.
Bu
t if
yo
u d
ecid
e to
get
up
an
d b
oo
gie
, p
reca
p-
illa
ry s
ph
inct
ers
wil
l se
nse
th
e d
eman
d f
or
mo
re b
loo
d
flo
w t
o y
ou
r m
usc
les
to d
eliv
er o
xy
gen
an
d c
arry
aw
ay
carb
on
dio
xid
e. M
any
mo
re o
f th
e sp
hin
cter
s w
ill
rela
x,
allo
win
g a
ru
sh o
f b
loo
d i
nto
th
e m
usc
le t
issu
e. T
he
sam
e
mec
han
ism
bri
ng
s b
loo
d t
o t
he
surf
ace
of
yo
ur
skin
wh
en
yo
u b
lush
or
bec
om
e fl
ush
ed w
ith
hea
t.
Take-Home Message
What
is t
he f
unctio
n o
f cap
illaries?
•T
he c
ard
iovascula
r syste
m’s
exte
nsiv
e n
etw
ork
of
narr
ow
cap
illaries e
nsure
s t
hat
every
liv
ing
cell
is o
nly
a s
ho
rt d
ista
nce
fro
m a
cap
illary
.
•In
cap
illary
bed
s,
sub
sta
nces m
ove b
etw
een t
he b
loo
d a
nd
extr
acellu
lar
fluid
by d
iffu
sio
n,
thro
ug
h c
ap
illary
po
res,
or
by
bulk
flo
w.
•M
ovem
ents
of
wate
r and
oth
er
sub
sta
nces into
and
out
of
cap
illaries h
elp
main
tain
blo
od
pre
ssure
and
the p
rop
er
fluid
bala
nce b
etw
een b
loo
d a
nd
tis
sues.
134
CHAPTER 7
Cardiovascular Disease
7.8
Wh
at a
re y
ou
r ch
ance
s o
f d
evel
op
ing
a c
ard
iov
ascu
lar
dis
ord
er?
So
me
maj
or
risk
fac
tors
in
clu
de
a fa
mil
y h
isto
ry
of
hea
rt
tro
ub
le,
hig
h
lev
els
of
blo
od
li
pid
s su
ch
as
cho
lest
ero
l an
d t
ran
s fa
ts, h
yp
erte
nsi
on
, ob
esit
y, s
mo
kin
g,
lack
of
exer
cise
, an
d s
imp
ly g
etti
ng
old
er.
Inte
rest
ing
ly,
ho
wev
er,
mo
re
than
h
alf
of
peo
ple
w
ho
su
ffer
h
eart
atta
cks
do
no
t h
ave
any
of
thes
e ri
sk f
acto
rs.
To
hel
p e
xp
lain
th
is p
uz
zle
, sc
ien
tist
s h
av
e fo
cuse
d
on
in
fla
mm
ati
on
, w
hic
h i
s a
def
ense
res
po
nse
dis
cuss
ed
in
Ch
ap
ter
9.
So
met
imes
, th
ou
gh
, in
fla
mm
ati
on
d
oes
ha
rm.
In t
he
card
iov
asc
ula
r sy
stem
, it
ca
n p
rom
ote
th
e
form
ati
on
o
f th
e a
rter
y-b
lock
ing
p
laq
ues
d
escr
ibed
sho
rtly
. In
fect
ion
s ca
n t
rig
ger
in
fIa
mm
ati
on
, w
hic
h i
n
turn
ca
use
s th
e li
ver
to
ma
ke
C-r
eact
ive
pro
tein
, w
hic
h
als
o
is
imp
lica
ted
in
h
eart
d
isea
se.
Th
is
lin
k
is
wh
y
infe
ctio
n-r
ela
ted
in
fla
mm
ati
on
a
nd
C
-rea
ctiv
e p
rote
in
are
lis
ted
in
Ta
ble
7.2
.
An
oth
er s
usp
ect
is h
om
ocy
stei
ne,
an
am
ino
aci
d t
hat
is
rele
ased
as
cert
ain
pro
tein
s ar
e b
rok
en d
ow
n.
To
o m
uch
of
it i
n t
he
blo
od
als
o m
ay c
ause
dam
age
that
is
a fi
rst
step
in
a m
ajo
r ca
rdio
vas
cula
r d
iso
rder
, at
her
osc
lero
sis.
Arteries can clog or weaken
Inar
teri
oscl
eros
is,
or
“har
den
ing
of
the
arte
ries
,” a
rter
ies
bec
om
e th
ick
er
an
d
stif
fer.
In
a
the
rosc
lero
sis
, th
is
con
dit
ion
get
s w
ors
e as
ch
ole
ster
ol
and
oth
er l
ipid
s b
uil
d
up
in
th
e ar
tery
wal
l. W
hen
th
is a
the
rosc
lero
tic
pla
qu
e
gro
ws
larg
e en
ou
gh
to
pro
tru
de
into
th
e ar
tery
, th
ere
is
less
ro
om
fo
r b
loo
d (
Fig
ure
7.1
8).
Co
ron
ary
art
erie
s an
d t
hei
r b
ran
ches
are
nar
row
an
d
vu
lner
able
to
clo
gg
ing
by
pla
qu
es.
Wh
en t
he
arte
ry i
s
nar
row
ed f
urt
her
to
on
e-q
uar
ter
of
its
star
tin
g d
iam
eter
,
sym
pto
ms
can
ran
ge
fro
m m
ild
ch
est
pai
n,
call
ed a
ng
ina
pec
tori
s, t
o a
fu
ll-s
cale
hea
rt a
ttac
k.
Hav
ing
to
o m
any
lip
ids
in t
he
blo
od
—o
ften
, d
ue
to a
die
t h
igh
in
ch
ole
ster
ol
and
tra
ns
fat—
is a
maj
or
risk
fac
tor
for
ath
ero
scle
rosi
s.
In
the
blo
od
, p
rote
ins
call
ed L
DL
s
(low
-den
sity
lip
opro
tein
s) b
ind
ch
ole
ster
ol
and
oth
er f
ats
an
d
carr
y
them
to
b
od
y
cell
s.
Pro
tein
s ca
lled
H
DL
s
(hig
h-d
ensi
ty l
ipop
rote
ins)
pic
k u
p c
ho
lest
ero
l in
th
e b
loo
d
an
d c
arr
y i
t b
ack
to
th
e li
ver
, w
her
e it
is
mix
ed i
nto
bil
e
an
d
even
tua
lly
ex
cret
ed
in
fece
s.
Bec
au
se
HD
Ls
hel
p
rem
ov
e ex
cess
ch
ole
ster
ol
fro
m t
he
bo
dy,
th
ey a
re c
all
ed
“g
oo
d c
ho
lest
ero
l.”
If t
her
e ar
e m
ore
LD
Ls
in t
he
blo
od
th
an c
ells
can
rem
ov
e, t
he
surp
lus
incr
ease
s th
e ri
sk o
f at
her
osc
lero
sis.
Th
is i
s w
hy
LD
Ls
are
call
ed “
bad
ch
ole
ster
ol.
” A
s L
DL
s
infi
ltra
te
art
ery
w
all
s,
cho
lest
ero
l a
ccu
mu
late
s th
ere.
Oth
er c
han
ges
occ
ur
also
, an
d e
ven
tual
ly a
fib
rou
s n
et
form
s o
ver
th
e m
ass—
an a
ther
osc
lero
tic
pla
qu
e. B
loo
d
test
s m
easu
re t
he
rela
tiv
e am
ou
nts
of
HD
Ls
and
LD
Ls
in
a p
erso
n’s
blo
od
(in
mil
lig
ram
s). A
tota
l o
f 20
0 m
g o
r le
ss
per
mil
lili
ter
of
blo
od
is
con
sid
ered
acc
epta
ble
(fo
r m
ost
peo
ple
), b
ut
exp
erts
ag
ree
that
LD
Ls
sho
uld
mak
e u
p o
nly
abo
ut
on
e-th
ird
of
this
to
tal,
or
abo
ut
70 t
o 8
0 m
g.
Su
rger
y
ma
y
be
the
on
ly
an
swer
fo
r a
se
ver
ely
blo
cked
coro
na
ry a
rter
y. I
n a
cor
onar
y b
yp
ass,
a s
ecti
on
of
a la
rge
ves
sel
tak
en f
rom
th
e ch
est
is s
titc
hed
to
th
e ao
rta
and
to
th
e co
ron
ary
ar
tery
b
elo
w
the
affe
cted
re
gio
n
(Fig
ure
7.1
8c).
In
las
er a
ng
iop
last
y,
lase
r b
eam
s v
apo
rize
the
pla
qu
es.
In
ball
oon
an
gio
pla
sty
, a
smal
l b
allo
on
is
infl
ated
in
sid
e a
blo
cked
art
ery
to
fla
tten
a p
laq
ue
so
ther
e is
mo
re r
oo
m i
n t
he
arte
ry.
Asm
all
wir
e cy
lin
der
call
ed a
ste
nt
may
th
en b
e in
sert
ed t
o h
elp
kee
p t
he
arte
ry
op
en.
“P
laq
ue-
bu
stin
g”
d
rug
s ca
lled
st
ati
ns,
w
hic
h
red
uce
ch
ole
ster
ol
in t
he
blo
od
, ca
n h
elp
pre
ven
t n
ew
pla
qu
es f
rom
fo
rmin
g.
Dis
ease
, an
in
jury
, o
r an
in
bo
rn d
efec
t ca
n w
eak
en a
n
arte
ry
so
that
p
art
of
its
wal
l b
allo
on
s o
utw
ard
. T
his
Figure 7.18
Pla
qu
es a
nd
blo
od
clo
ts m
ay c
log
art
eri
es.
Sectio
n f
rom
(a
) a n
orm
al art
ery
, (b
) a b
loo
d v
essel
narr
ow
ed
by a
pla
que a
nd
clo
gg
ed
furt
her
by a
blo
od
clo
t. (
c)
Co
ronary
byp
asses.
unobstructed
lumen of
normal artery
wall of artery
narrowed
lumen
blood clot
sticking to
plaque
atherosclerotic
plaque
ba
a shunt made
of a section
taken from one
of the patient’s
other blood vessels
aorta
coronary
artery
blockage
c
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
135
bea
ts
per
m
inu
te,
call
ed
tach
yca
rdia
, o
ccu
rs
no
rma
lly
du
rin
g e
xer
cise
or
stre
ssfu
l si
tuat
ion
s. S
erio
us
tach
yca
rdia
can
be
trig
ger
ed b
y d
rug
s (i
ncl
ud
ing
ca
ffei
ne,
nic
oti
ne,
alc
oh
ol,
an
d c
oca
ine)
, ex
cess
ive
thy
roid
ho
rmo
nes
, a
nd
oth
er f
act
ors
.
Ven
tric
ula
r fi
bril
lati
onis
th
e m
ost
dan
ger
ou
s ar
ryth
mia
.
In p
arts
of
the
ven
tric
les,
th
e ca
rdia
c m
usc
le c
on
trac
ts
hap
haz
ard
ly,
so
blo
od
is
n’t
p
um
ped
n
orm
ally
. T
his
is
wh
at h
app
ens
in s
ud
den
car
dia
c ar
rest
, as
des
crib
ed i
n
the
cha
pte
r in
tro
du
ctio
n.
Lik
e M
att
N
ad
er’s
ca
rdia
c
arre
st d
escr
ibed
in
th
e ch
apte
r in
tro
du
ctio
n,
ven
tric
ula
r
fib
rill
atio
n i
s a
med
ical
em
erg
ency
. W
ith
lu
ck,
a st
ron
g
elec
tric
al jo
lt t
o t
he
pat
ien
t’s
hea
rt f
rom
an
AE
D, o
r th
e u
se
of
def
ibri
llat
ing
dru
gs,
can
res
tore
a n
orm
al r
hy
thm
bef
ore
the
dam
age
is t
oo
ser
iou
s.
A heart-healthy lifestyle may help
prevent cardiovascular disease
Ev
ery
bo
dy
ag
es,
and
no
ne
of
us
can
co
ntr
ol
the
gen
es w
e
inh
erit
. E
ven
so
, ea
ch o
f u
s ca
n t
ake
step
s to
im
pro
ve
ou
r
chan
ces
of
liv
ing
fre
e o
f se
rio
us
card
iov
ascu
lar
dis
ease
.
Wat
chin
g o
ur
inta
ke
of
foo
ds
rich
in
ch
ole
ster
ol
and
tra
ns
fats
, g
etti
ng
reg
ula
r ex
erci
se,
and
no
t sm
ok
ing
are
th
ree
stra
teg
ies,
an
d
they
p
rov
ide
mu
ltip
le
ben
efit
s.
Ad
iet
that
’s m
od
erat
e in
fat
s m
ay a
lso
hel
p k
eep
wei
gh
t u
nd
er
con
tro
l. E
xer
cise
hel
ps
wit
h w
eig
ht
con
tro
l, t
oo
. It
als
o
reli
eves
str
ess
and
hel
ps
kee
p m
usc
les
and
bo
nes
fit
an
d
stro
ng
. S
mo
kin
g i
s b
ad f
or
just
ab
ou
t ev
ery
bo
dy
sy
stem
;
yo
u’l
l g
et a
clo
ser
loo
k a
t it
s d
evas
tati
ng
im
pac
t o
n t
he
resp
irat
ory
sy
stem
in
Ch
apte
r 10
.
po
uch
lik
e w
eak
sp
ot
is c
alle
d a
n a
ne
ury
sm
. A
neu
rysm
s
can
dev
elo
p i
n v
ario
us
par
ts o
f th
e ca
rdio
vas
cula
r sy
stem
,
incl
ud
ing
ves
sels
in
th
e b
rain
, ab
do
men
, an
d t
he
aort
a. I
f
an a
neu
rysm
bu
rsts
, it
can
cau
se s
erio
us
and
ev
en f
atal
blo
od
lo
ss.
Am
ino
r a
neu
rysm
m
ay
n
ot
pre
sen
t
any
im
med
iate
w
orr
y,
bu
t in
th
e b
rain
, es
pec
iall
y,
an
aneu
rysm
is
p
ote
nti
ally
so
d
ang
ero
us
that
it
re
qu
ires
imm
edia
te m
edic
al t
reat
men
t.
Heart damage can lead to heart attack
and heart failure
Ah
ea
rt a
tta
ck
is d
amag
e to
or
dea
th o
f h
eart
mu
scle
.
War
nin
g s
ign
s o
f a
hea
rt a
ttac
k i
ncl
ud
e se
nsa
tio
ns
of
pai
n
or
squ
eezi
ng
beh
ind
th
e b
reas
tbo
ne,
pai
n o
r n
um
bn
ess
rad
iati
ng
d
ow
n
the
left
a
rm,
swea
tin
g,
an
d
na
use
a.
Wo
men
m
ore
o
ften
ex
per
ien
ce
nec
k
an
d
ba
ck
pa
in,
fati
gu
e, a
sen
se o
f in
dig
esti
on
, a
fast
hea
rtb
eat,
sh
ort
nes
s
of
bre
ath
, an
d l
ow
blo
od
pre
ssu
re.
Ris
k f
acto
rs i
ncl
ud
e
hy
per
ten
sio
n,
a ci
rcu
lati
ng
b
loo
d
clo
t (a
lso
ca
lled
an
emb
olu
s),
and
ath
ero
scle
rosi
s.
Inh
ea
rt fa
ilu
re(H
F),
th
e h
eart
is
wea
ken
ed a
nd
so
do
es n
ot
pu
mp
blo
od
as
wel
l as
it
sho
uld
. E
ven
a b
asic
exer
tio
n s
uch
as
wal
kin
g c
an b
eco
me
dif
ficu
lt.
Bec
ause
pat
ien
ts
may
re
qu
ire
rep
eate
d
ho
spit
aliz
atio
n,
HF
h
as
bec
om
e th
e n
atio
n’s
mo
st c
ost
ly h
ealt
h p
rob
lem
.
Arrhythmias are abnormal heart rhythms
An
el
ectr
oca
rdio
gra
m,
or
EC
G,
is
a
reco
rdin
g
of
the
elec
tric
al
act
ivit
y
of
the
card
iac
cycl
e (F
igu
re
7.1
9a)
.
EC
Gs
rev
eal
arr
hyth
mia
s,
or
irre
gu
lar
hea
rt r
hy
thm
s.
So
me
arr
hy
thm
ias
are
a
bn
orm
al,
o
ther
s a
re
no
t.
Fo
r
exa
mp
le,
end
ura
nce
ath
lete
s m
ay
ha
ve
a b
elo
w-a
ver
ag
e
rest
ing
car
dia
c ra
te, o
r br
ady
card
ia, w
hic
h i
s an
ad
apta
tio
n
to r
egu
lar
stre
nu
ou
s ex
erci
se.
Aca
rdia
c ra
te a
bo
ve
10
0
Figure 7.19Animated!
An
EC
G t
rac
ing
ca
n r
eve
al a
bn
orm
al
he
art
ac
tivit
y.
(a)
EC
G o
f a n
orm
al
heart
beat.
The P
wave is g
enera
ted
by e
lectr
ical sig
nals
fro
m t
he S
A
no
de t
hat
stim
ula
te c
ontr
actio
n o
f
the a
tria
. A
s t
he s
tim
ulu
s m
oves
over
the v
entr
icle
s,
it is r
eco
rded
as t
he Q
RS
wave c
om
ple
x.
The T
wave m
ark
s t
he b
rief
perio
d w
hen
the v
entr
icle
s a
re r
esting
. (b
) A
reco
rdin
g o
f ventr
icula
r fib
rilla
tio
n.
ventricular
fibrillation
ab
R
PT
SQ
00.2
0.4
0.6
0.8
time (seconds)
TABLE 7.2
Major Risk Factors
for Cardiovascular Disease
1.
Inh
eri
ted
pre
dis
po
sit
ion
2.
Ele
vate
d b
loo
d lip
ids
(ch
ole
ste
rol, t
ran
s f
ats
)
3.
Hyp
ert
en
sio
n
4.
Ob
esit
y
5.
Sm
okin
g
6.
Lack o
f exerc
ise
7.
Ag
e 5
0+
8.
Inflam
mati
on
du
e t
o in
fecti
on
s b
y v
iru
ses,
bacte
ria
9.
Hig
h levels
of
C-r
eacti
ve p
rote
in in
blo
od
10
.E
levate
d b
loo
d levels
of
the a
min
o a
cid
ho
mo
cyste
ine
Image not available due to copyright restrictions
136
CHAPTER 7
Infections, Cancer, and Heart Defects
7.9
Infections may seriously damage the heart
As
des
crib
ed i
n S
ecti
on
7.8
, b
acte
rial
an
d v
iral
in
fect
ion
s
that
fir
st t
ake
ho
ld o
uts
ide
the
card
iov
ascu
lar
syst
em m
ay
even
tua
lly
h
arm
th
e h
eart
. In
fect
ion
s re
late
d
to
an
un
trea
ted
“st
rep
th
roat
,” c
erta
in d
enta
l p
roce
du
res,
or
IV
dru
g a
bu
se a
re i
n t
his
cat
ego
ry.
“Str
ep”
infe
ctio
ns
are
cau
sed
by
str
ain
s o
f S
trep
toco
ccu
s
bac
teri
a (F
igu
re 7
.20)
. If
th
e il
lnes
s is
n’t
tre
ated
wit
h a
n
anti
bio
tic,
it
may
lea
d t
o r
heu
mat
ic f
ever
. In
th
is d
iso
rder
,
the
bo
dy
pro
du
ces
def
ensi
ve
anti
bo
die
s th
at a
ttac
k t
he
inv
adin
g b
acte
ria—
bu
t th
ey a
lso
mis
tak
enly
att
ack
hea
rt
val
ves
. A
lth
ou
gh
in
aff
luen
t co
un
trie
s m
ost
peo
ple
wh
o
dev
elo
p a
str
ep i
nfe
ctio
n g
et t
reat
men
t, r
heu
mat
ic f
ever
stil
l is
th
e m
ost
co
mm
on
cau
se o
f h
eart
val
ve
dis
ease
. It
is
an e
xam
ple
of
an a
uto
imm
un
e d
iso
rder
, a
top
ic w
e w
ill
dis
cuss
in
Ch
apte
r 9.
Mic
rob
es t
hat
en
ter
the
blo
od
stre
am d
uri
ng
den
tal
sur-
ger
y o
r o
n a
co
nta
min
ated
IV
nee
dle
may
att
ack
hea
rt
va
lves
d
irec
tly.
T
his
co
nd
itio
n
is
call
ed
end
ocar
dit
is
(“in
sid
e th
e h
eart
”).
Peo
ple
wh
o h
ave
an e
xis
tin
g v
alv
e
pro
ble
m d
ue
to a
gin
g o
r so
me
oth
er h
eart
dis
ord
er o
ften
are
adv
ised
to
ta
ke
an
anti
bio
tic
bef
ore
h
avin
g
den
tal
wo
rk.
En
do
card
itis
is
a m
ajo
r h
azar
d f
or
IV d
rug
use
rs.
It
can
ra
pid
ly
des
tro
y
infe
cted
v
alv
es
and
ca
use
su
dd
en
hea
rt f
ailu
re.
Hea
rt p
rob
lem
s al
so c
an b
e a
com
pli
cati
on
of
Ly
me
dis
-
ease
, w
hic
h i
s ca
use
d b
y t
he
bac
teri
um
Bor
reli
a bu
rgdo
rfer
i
and
sp
read
by
tic
ks.
At
firs
t th
e b
od
y r
esp
on
ds
to a
Ly
me
infe
ctio
n w
ith
a “
bu
ll’s
-ey
e” r
ash
(F
igu
re 7
.21)
. L
ater
th
e
join
ts m
ay b
eco
me
infl
amed
, an
d s
o m
ay t
he
hea
rt m
usc
le
(th
e m
yo
card
ium
). H
eart
in
flam
mat
ion
, cal
led
myo
card
itis
,
pro
du
ces
an
irre
gu
lar
hea
rt
rhy
thm
th
at
man
ifes
ts
as
diz
zy s
pel
ls a
nd
oth
er o
ther
sy
mp
tom
s. M
easl
es c
ause
d
by
th
e ru
bel
la v
iru
s in
un
vac
cin
ated
peo
ple
can
als
o d
am-
age
the
hea
rt m
usc
le.
Alc
oh
ol
abu
se a
nd
rec
reat
ion
al d
rug
s al
so m
ay c
ause
hea
rt
infl
amm
atio
n.
Wh
en
som
eon
e d
ies
of
a co
cain
e
ov
erd
ose
, an
au
top
sy o
ften
rev
eals
my
oca
rdit
is.
Co
cain
e,
amp
het
amin
es,
and
hab
itu
al,
hea
vy
alc
oh
ol
use
all
can
cau
se c
ard
iom
yo
pat
hy,
or
wea
kn
ess
of
the
hea
rt m
usc
le
that
in
tu
rn m
ay l
ead
to
hea
rt f
ailu
re.
Is there such a thing as heart cancer?
Alt
ho
ug
h t
he
rea
son
is
a m
yst
ery,
ca
nce
r a
lmo
st n
ever
sta
rts
in t
he
hea
rt m
usc
le o
r b
loo
d v
esse
ls.
Mo
re o
ften
, a
can
cer
tha
t b
egin
s el
sew
her
e in
th
e b
od
y, s
uch
as
the
skin
can
cer
ma
lig
na
nt
mel
an
om
a s
pre
ad
s to
th
e h
eart
. E
ven
mo
re c
om
mo
nly
, th
e h
eart
or
ves
sels
are
da
ma
ged
by
can
cer
trea
tmen
ts s
uch
as
rad
iati
on
or
chem
oth
era
py.
Inborn heart defects are fairly common
Yo
u m
ay
ha
ve
hea
rd o
f “
blu
e b
ab
ies,
” i
nfa
nts
bo
rn w
ith
a h
ole
in
so
me
pa
rt o
f th
e h
eart
wa
ll,
so t
ha
t th
e h
eart
do
esn
’t
pu
mp
b
loo
d
effi
cien
tly.
In
fa
ct,
tho
usa
nd
s o
f
ba
bie
s en
ter
the
wo
rld
ea
ch y
ear
wit
h s
om
e ty
pe
of
hea
rt
def
ect.
Dep
end
ing
on
th
e p
rob
lem
, on
e o
r m
ore
su
rger
ies
ma
y b
e re
qu
ired
to
rep
air
it.
Figure 7.20
Str
ep
toco
ccu
sb
ac
teri
a c
au
se
dif
fere
nt
kin
ds o
f “s
tre
p”
infe
cti
on
s.
In t
his
im
ag
e t
he b
acte
ria a
re
co
lore
d g
reen.
actual size:
Image not available due to copyright restrictions
CONNECTIONS: The Cardiovascular System and Blood in Homeostasis
7.10
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
137
The Cardiovascular
System and Blood
As d
escribed in C
hapte
r 8, blood
is the m
edium that transports
nutrients, oxygen, horm
ones, cell
waste
s, and o
ther substa
nces.
It also carries and d
istribute
s a
gre
at deal of body heat.
The heart p
umps b
lood into
blood
vessels that transport b
lood
thro
ughout th
e b
ody. In this w
ay
the syste
m d
elivers b
lood’s
carg
oes to b
ody cells and carries
away p
ote
ntially toxic w
aste
s
and o
ther unneeded m
ate
rials.
Blood p
ressure
genera
ted b
y
heart contractions helps keep
blood flowing thro
ugh the
card
iovascular syste
m.
Mechanisms that widen o
r narrow
the d
iamete
r of arterioles and
capillaries allow adjustm
ents in
blood flow to d
iffere
nt body
regions as conditions w
arrant.
Blood’s ability to clot allows the
body to susta
in m
inor wounds
without a serious loss o
f blood.
Inte
gumenta
ry
syste
m
Skeleta
l syste
m
Muscular syste
m
Immunity and
the lymphatic
syste
m
Digestive
syste
m
Respirato
ry
syste
m
Urinary
syste
m
Nervous syste
m
Sensory
syste
ms
Endocrine syste
m
Repro
ductive
syste
m
Adjustm
ents to b
lood flow at th
e skin’s
surface help regulate
body tempera
ture
.
Blood clotting m
echanisms help repair
skin injuries.
Ste
m cells in b
one m
arrow p
roduce b
lood
cells. Circulating b
lood d
elivers calcium and
phosphate
used to form
bone tissue.
Circulating b
lood d
istribute
s heat pro
duced
by active skeleta
l muscles. Contraction o
f leg
muscles helps retu
rn venous b
lood to the
heart.
Blood p
umped b
y the heart p
icks up inhaled
oxygen fro
m the lungs and d
elivers carb
on
dioxide to the lungs to b
e exhaled.
The b
loodstream circulate
s nutrients fro
m
food d
igestion to cells. The liver re
ceives and
pro
cesses certain nutrients via the hepatic
portal syste
m.
Blood p
umped b
y the heart p
icks up inhaled
oxygen fro
m the lungs and d
elivers carb
on
dioxide to the lungs to b
e exhaled.
The kidneys filte
r im
purities and o
ther
unneeded substa
nces fro
m b
lood and form
urine that re
moves them fro
m the b
ody. The
kidney horm
one ery
thro
poietin stimulate
s
the form
ation o
f re
d b
lood cells.
Cente
rs in the b
rain and spinal cord
adjust th
e
rate
and strength
of heart contractions and
help m
ainta
in p
roper blood p
ressure
by
adjusting the d
iamete
r of arterioles.
Sensors in the caro
tid arteries help m
onitor
blood p
ressure
. Sensory
perceptions relate
d
to m
enta
l or physiological sta
tes m
ay trigger
changes in local blood flow (as in b
lushing,
sexual aro
usal).
Nearly all horm
ones reach their targ
ets via
the b
loodstream. Certain cells in the heart
atria release a horm
one (ANP) th
at helps
regulate
blood p
ressure
.
Repro
ductive horm
ones, including estrogens
and testo
ste
rone, travel in the b
loodstream.
Arterioles in o
rgans o
f sexual inte
rcourse
dilate
at times o
f aro
usal. B
lood vessels o
f
the p
lacenta
help m
ainta
in homeosta
sis in a
developing fetu
s.
138
CHAPTER 7Be Not Still, My Beating
Heart!
IMPACTS,
ISSUES
How W
ould You V
ote?
Wo
uld
yo
u b
e in f
avo
r o
f m
and
ato
ry C
PR
tra
inin
g in
hig
h s
cho
ols
? S
ee C
eng
ag
eN
OW
fo
r d
eta
ils,
then
vo
te o
nlin
e.
Summary
Section7.1
Th
e ca
rdio
va
scu
lar
syst
em
con
sist
s o
f th
e
hea
rt
an
d
blo
od
v
esse
ls
incl
ud
ing
a
rter
ies,
a
rter
iole
s,
cap
illa
ries
, v
enu
les,
an
d v
ein
s. T
he
syst
em h
elp
s m
ain
tain
ho
meo
sta
sis
by
p
rov
idin
g
rap
id
inte
rna
l tr
an
spo
rt
of
sub
sta
nce
s to
an
d f
rom
cel
ls.
�Use the anim
ation and inte
raction o
nCengageNOW
to explore
the human
card
iovascular syste
m.
Section7.2
Th
e h
eart
mu
scle
is
call
ed t
he
my
oca
rdiu
m.
Ase
ptu
m d
ivid
es t
he
hea
rt i
nto
tw
o h
alv
es,
each
wit
h t
wo
cha
mb
ers,
an
atr
ium
an
d a
ven
tric
le.
Va
lves
in
ea
ch h
alf
hel
p c
on
tro
l th
e d
irec
tio
n o
f b
loo
d f
low
.T
hes
e in
clu
de
a
sem
ilu
na
r v
alv
e a
nd
an
atr
iov
entr
icu
lar
va
lve.
Co
ron
ary
art
erie
s p
rov
ide
mu
ch o
f th
e h
eart
’s b
loo
d s
up
ply
. T
hey
bra
nch
off
th
e a
ort
a,
wh
ich
ca
rrie
s o
xy
gen
ate
d b
loo
d a
wa
y
fro
m t
he
hea
rt.
Blo
od
is
pu
mp
ed e
ach
tim
e th
e h
eart
bea
ts,
in a
ca
rdia
c
cycl
e o
f co
ntr
act
ion
an
d r
ela
xa
tio
n.
Sy
sto
le,
the
con
tra
c-
tio
n
ph
ase
, a
lter
na
tes
wit
h
the
rela
xa
tio
n
ph
ase
, ca
lled
dia
sto
le.
�Use the anim
ation and inte
raction o
nCengageNOW
to learn
about th
e structu
reand function o
f th
e heart.
Section7.3
Th
e
pa
rtit
ion
b
etw
ee
n
the
h
ea
rt’s
tw
o
ha
lves
sep
ara
tes
the
blo
od
flo
w i
nto
tw
o c
ircu
its,
on
e p
ul-
mo
na
ry a
nd
th
e o
ther
sy
stem
ic.
a.
In t
he
pu
lmo
na
ry c
ircu
it,
deo
xy
gen
ate
d b
loo
d i
n t
he
hea
rt’s
rig
ht
ha
lf i
s p
um
ped
to
ca
pil
lary
bed
s in
th
e lu
ng
s.
Th
e b
loo
d p
ick
s u
p o
xy
gen
, th
en f
low
s to
th
e h
eart
’s l
eft
atr
ium
.
b.
In t
he
syst
emic
cir
cuit
, th
e le
ft h
alf
of
the
hea
rt p
um
ps
ox
yg
ena
ted
b
loo
d
to
bo
dy
ti
ssu
es.
Th
ere,
ce
lls
tak
e u
p
ox
yg
en a
nd
rel
ease
ca
rbo
n d
iox
ide.
Th
e b
loo
d, n
ow
deo
xy
-
gen
ate
d,
flo
ws
to t
he
hea
rt’s
rig
ht
atr
ium
.
Section7.4
Ele
ctri
cal
imp
uls
es s
tim
ula
te h
eart
co
ntr
ac-
tio
ns
via
th
e h
eart
’s c
ard
iac
con
du
ctio
n s
yst
em. I
n t
he
rig
ht
atr
ium
, a
sin
oa
tria
l n
od
e—th
e ca
rdia
c p
ace
ma
ker
—g
ener
-
ate
s th
e im
pu
lses
a
nd
es
tab
lish
es
a
reg
ula
r h
eart
bea
t.
Sig
na
ls f
rom
th
e S
An
od
e p
ass
to
th
e a
trio
ven
tric
ula
r n
od
e,
a w
ay
sta
tio
n f
or
stim
ula
tio
n t
ha
t tr
igg
ers
con
tra
ctio
n o
f
the
ven
tric
les.
T
he
ner
vo
us
an
d
end
ocr
ine
syst
ems
can
ad
just
th
e ra
te a
nd
str
eng
th o
f h
eart
co
ntr
act
ion
s.
Section7.5
Blo
od
pre
ssu
re i
s th
e fl
uid
pre
ssu
re b
loo
d
exer
ts a
ga
inst
ves
sel
wa
lls.
It
is h
igh
est
in t
he
ao
rta
, w
hic
h
rece
ives
blo
od
pu
mp
ed b
y t
he
left
ven
tric
le,
an
d d
rop
s
alo
ng
th
e sy
stem
ic c
ircu
it.
�Use the anim
ation and inte
raction o
nCengageNOW
to see how b
lood p
ressure
is m
easure
d.
Section7.6
a.
Art
erie
s a
re s
tro
ng
, el
ast
ic p
ress
ure
res
erv
oir
s. T
hey
smo
oth
o
ut
pre
ssu
re
cha
ng
es
resu
ltin
g
fro
m
hea
rtb
eats
an
d s
o s
mo
oth
ou
t b
loo
d f
low
. W
hen
a v
entr
icle
co
ntr
act
s,
it c
au
ses
a p
ress
ure
su
rge,
or
pu
lse,
in
la
rge
art
erie
s.
b.
Art
eri
ole
s a
re
con
tro
l p
oin
ts
for
dis
trib
uti
ng
dif
fere
nt
vo
lum
es o
f b
loo
d t
o d
iffe
ren
t re
gio
ns.
c.C
ap
illa
ry b
eds
are
dif
fusi
on
zo
nes
wh
ere
blo
od
an
d
extr
ace
llu
lar
flu
id e
xch
an
ge
sub
sta
nce
s.
d.
Ven
ule
s o
ver
lap
ca
pil
lari
es a
nd
vei
ns
som
ewh
at
in
fun
ctio
n.
So
me
solu
tes
dif
fuse
acr
oss
th
eir
wa
lls.
e.V
ein
s a
re
blo
od
re
serv
oir
s th
at
can
b
e ta
pp
ed
to
ad
just
th
e v
olu
me
of
flo
w b
ack
to
th
e h
eart
. V
alv
es i
n s
om
e
vei
ns,
in
th
e li
mb
s, p
rev
ent
blo
od
ret
urn
ing
to
th
e h
eart
fro
m f
low
ing
ba
ckw
ard
du
e to
gra
vit
y.
Blo
od
v
esse
ls
hel
p
con
tro
l b
loo
d
pre
ssu
re.
Art
erio
les
dil
ate
wh
en c
ente
rs i
n t
he
bra
in d
etec
t an
ab
no
rmal
ris
e in
blo
od
pre
ssu
re.
If b
loo
d p
ress
ure
fal
ls b
elo
w a
set
po
int,
th
e
cen
ters
tri
gg
er v
aso
con
stri
ctio
n o
f ar
teri
ole
s. B
aro
rece
pto
rs
in c
aro
tid
art
erie
s p
rov
ide
sho
rt-t
erm
blo
od
pre
ssu
re c
on
tro
l
by
way
of
sig
nal
s th
at a
dju
st t
he
pre
ssu
re w
hen
su
dd
en
chan
ges
occ
ur.
Section7.7
Ca
pil
lari
es
are
w
her
e fl
uid
s a
nd
so
lute
s
mo
ve
bet
wee
n t
he
blo
od
stre
am
an
d b
od
y c
ells
. T
hes
e su
b-
sta
nce
s m
ov
e b
y d
iffu
sio
n,
thro
ug
h p
ore
s b
etw
een
cel
ls,
an
d b
y b
ulk
flo
w o
f fl
uid
. T
he
mo
vem
ents
hel
p m
ain
tain
the
pro
per
flu
id b
ala
nce
bet
wee
n t
he
blo
od
an
d s
urr
ou
nd
-
ing
tis
sues
, a
nd
als
o h
elp
ma
inta
in p
rop
er b
loo
d v
olu
me.
Section7.8
Ca
rdio
va
scu
lar
dis
ord
ers
coll
ecti
vel
y
are
the
nu
mb
er o
ne
cau
se o
f d
eath
in
th
e U
nit
ed S
tate
s. I
n a
th-
ero
scle
rosi
s, a
bu
ild
up
of
cho
lest
ero
l a
nd
oth
er m
ate
ria
l
dev
elo
ps
into
pla
qu
es t
ha
t n
arr
ow
th
e in
teri
or
spa
ce i
n
art
erie
s a
nd
red
uce
blo
od
flo
w t
o t
he
hea
rt o
r o
ther
tis
sues
ALTHOUGH
the b
enefit
s o
f C
PR
tra
inin
g a
re o
bvi
ous,
schools
mig
ht
need
extr
a fund
ing in o
rder
to a
dd
a C
PR
min
i-cours
e.
Als
o,
som
e p
eop
le a
re u
ncom
fort
ab
le w
ith t
he id
ea o
f p
erform
ing m
outh
-to-m
outh
resuscita
tion,
esp
ecia
lly o
n s
om
eone t
hey
do n
ot
know
.
CIR
CULATIO
N: THE H
EART A
ND B
LOOD V
ESSELS
139
an
d o
rga
ns.
HD
Ls
(hig
h-d
ensi
ty l
ipo
pro
tein
s) h
elp
tra
ns-
po
rt
exce
ss
blo
od
ch
ole
ster
ol
to
the
liv
er
for
dis
po
sal.
Hig
h l
evel
s o
f L
DL
s (l
ow
-den
sity
lip
op
rote
ins)
an
d t
ran
s
fats
, sm
ok
ing
, o
bes
ity,
a
nd
in
fla
mm
ati
on
in
co
ron
ary
art
erie
s a
re s
om
e o
f th
e m
ajo
r ri
sk f
act
ors
ass
oci
ate
d w
ith
ath
ero
scle
rosi
s.
Dis
ease
, in
jury
, o
r a
n
inb
orn
d
efec
t ca
n
wea
ken
a
n
art
ery
so
th
at
pa
rt o
f it
s w
all
ba
llo
on
s o
utw
ard
an
d f
orm
s
an
an
eury
sm.
Oth
er s
erio
us
card
iov
asc
ula
r d
iso
rder
s a
re h
eart
att
ack
(da
ma
ge
to o
r d
eath
of
hea
rt m
usc
le)
an
d h
eart
fa
ilu
re
(a w
eak
ened
hea
rt t
ha
t ca
nn
ot
pu
mp
blo
od
eff
icie
ntl
y).
An
arr
hy
thm
ia—
irre
gu
lar
hea
rt
rhy
thm
—ca
n
be
a
sig
n
of
hea
rt p
rob
lem
s. T
he
mo
st s
erio
us
arr
hy
thm
ia i
s v
entr
icu
lar
fib
rill
ati
on
, h
ap
ha
za
rd c
on
tra
ctio
ns
of
the
ven
tric
les
tha
t
gre
atl
y r
edu
ce b
loo
d p
um
pin
g.
Section7.9
Infe
ctio
ns,
su
bst
an
ce
ab
use
, a
nd
b
irth
def
ects
all
ca
n r
esu
lt i
n d
am
ag
e to
th
e h
eart
mu
scle
or
hea
rt v
alv
es.
Review Questions
1.L
ist
the
fun
ctio
ns
of
the
card
iov
asc
ula
r sy
stem
.
2.
Def
ine
a “
hea
rtb
eat,
” g
ivin
g t
he
seq
uen
ce o
f ev
ents
tha
t m
ak
e it
up
.
3.
Dis
tin
gu
ish
bet
wee
n t
he
syst
emic
an
d p
ulm
on
ary
circ
uit
s.
4.
Ex
pla
in t
he
fun
ctio
n o
f (a
) th
e si
no
atr
ial
no
de,
(b)
th
ea
trio
ven
tric
ula
r n
od
e, a
nd
(c)
th
e ca
rdia
c p
ace
ma
ker
.
5.
Sta
te t
he
ma
in f
un
ctio
n o
f b
loo
d c
ap
illa
ries
. N
am
eth
e m
ain
wa
ys
sub
sta
nce
s cr
oss
th
e w
all
s o
fca
pil
lari
es.
6.
In t
he
dia
gra
m a
bo
ve,
la
bel
th
e h
eart
’s c
om
po
nen
ts.
7.
Sta
te t
he
ma
in f
un
ctio
ns
of
ven
ule
s a
nd
vei
ns.
Wh
at
forc
es w
ork
to
get
her
in
ret
urn
ing
ven
ou
s b
loo
d
to t
he
hea
rt?
Self-Quiz
An
sw
ers
in
Ap
pe
nd
ix V
1.C
ells
ob
tain
nu
trie
nts
fro
m a
nd
dep
osi
t w
ast
e in
to.
a.
blo
od
c.ea
ch o
ther
b.
lym
ph
ves
sels
d.
bo
th a
an
d b
2.
Th
e co
ntr
act
ion
ph
ase
of
the
hea
rtb
eat
is
; th
e re
lax
ati
on
ph
ase
is
.
3.
In t
he
pu
lmo
na
ry c
ircu
it,
the
hea
rt’s
h
alf
pu
mp
s b
loo
d t
o c
ap
illa
ry b
eds
insi
de
the
lun
gs;
th
en
blo
od
flo
ws
to t
he
hea
rt.
a.
left
; d
eox
yg
ena
ted
; o
xy
gen
ate
db
.ri
gh
t; d
eox
yg
ena
ted
; o
xy
gen
ate
dc.
left
; o
xy
gen
ate
d;
deo
xy
gen
ate
dd
.ri
gh
t; o
xy
gen
ate
d;
deo
xy
gen
ate
d
4.
In t
he
syst
emic
cir
cuit
, th
e h
eart
’s
ha
lfp
um
ps
blo
od
to
all
bo
dy
reg
ion
s; t
hen
blo
od
flo
ws
to t
he
hea
rt.
a.
left
; d
eox
yg
ena
ted
; o
xy
gen
ate
db
.ri
gh
t; d
eox
yg
ena
ted
; o
xy
gen
ate
dc.
left
; o
xy
gen
ate
d;
deo
xy
gen
ate
dd
.ri
gh
t; o
xy
gen
ate
d;
deo
xy
gen
ate
d
5.
Aft
er y
ou
ea
t, b
loo
d p
ass
ing
th
rou
gh
th
e G
I tr
act
tra
vel
s th
rou
gh
th
e to
a c
ap
illa
ry b
ed i
n t
he
.a
.a
ort
a;
liv
erb
.h
epa
tic
po
rta
l v
ein
; li
ver
c.h
epa
tic
vei
n;
sple
end
.re
na
l a
rter
ies;
kid
ney
s
6.
Th
e ca
rdia
c p
ace
ma
ker
.
a.
sets
th
e n
orm
al
rate
of
hea
rtb
eat
b.
is t
he
sam
e a
s th
e A
V n
od
ec.
esta
bli
shes
res
tin
g b
loo
d p
ress
ure
d.
all
of
thes
e a
re c
orr
ect
7.
Blo
od
pre
ssu
re i
s h
igh
est
in
an
d l
ow
est
in.
a.
art
erie
s; v
ein
sc.
art
erie
s; v
entr
icle
sb
.a
rter
ies;
rel
ax
ed a
tria
d.
art
erio
les;
vei
ns
8.
con
tra
ctio
n d
riv
es b
loo
d t
hro
ug
h t
he
syst
emic
an
d p
ulm
on
ary
cir
cuit
s; o
uts
ide
the
hea
rt,
blo
od
pre
ssu
re i
s h
igh
est
in t
he
.a
.A
tria
l; v
entr
icle
sc.
Ven
tric
ula
r; a
rter
ies
b.
Atr
ial;
atr
iad
.V
entr
icu
lar;
ao
rta
9.
Ma
tch
th
e ty
pe
of
blo
od
ves
sel
wit
h i
ts m
ajo
rfu
nct
ion
.a
rter
ies
a.
dif
fusi
on
art
erio
les
b.
con
tro
l o
f b
loo
d d
istr
ibu
tio
nca
pil
lari
esc.
tra
nsp
ort
, b
loo
d v
olu
me
vei
ns
rese
rvo
irs
d.
blo
od
tra
nsp
ort
an
d p
ress
ure
reg
ula
tors
140
CHAPTER 7
10.
Ma
tch
th
ese
thre
e ci
rcu
lati
on
co
mp
on
ents
wit
h t
hei
rd
escr
ipti
on
s.ca
pil
lary
bed
sa
.tw
o a
tria
, tw
o v
entr
icle
sh
eart
ch
am
ber
sb
.d
riv
ing
fo
rce
for
blo
od
hea
rt c
on
tra
ctio
ns
c.z
on
es o
f d
iffu
sio
n
Critical Thinking
1.A
pat
ien
t su
ffer
ing
fro
m h
yp
erte
nsi
on
may
rec
eiv
ed
rug
s th
at d
ecre
ase
the
hea
rt’s
ou
tpu
t, d
ilat
e ar
teri
ole
s,o
r in
crea
se u
rin
e p
rod
uct
ion
. In
eac
h c
ase,
ho
w w
ou
ldth
e d
rug
tre
atm
ent
hel
p r
elie
ve
hy
per
ten
sio
n?
2.
Hea
vy
sm
ok
ers
oft
en d
evel
op
ab
no
rma
lly
hig
h
blo
od
pre
ssu
re.
Th
e n
ico
tin
e in
to
ba
cco
is
a p
ote
nt
va
soco
nst
rict
or.
Ex
pla
in t
he
con
nec
tio
n b
etw
een
thes
e tw
o f
act
s, i
ncl
ud
ing
wh
at
kin
d o
f b
loo
d v
esse
lsa
re l
ikel
y a
ffec
ted
.
3.
Bef
ore
an
tib
ioti
cs w
ere
av
ail
ab
le,
it w
asn
’t u
nco
mm
on
for
peo
ple
in
th
e U
nit
ed S
tate
s (a
nd
els
ewh
ere)
to
dev
elo
p r
heu
ma
tic
fev
er.
Th
e in
fect
ion
ca
n t
rig
ger
a
n i
nfl
am
ma
tio
n t
ha
t u
ltim
ate
ly d
am
ag
es v
alv
es i
nth
e h
eart
. H
ow
mu
st t
his
dis
ease
aff
ect
the
hea
rt’s
fun
ctio
nin
g?
Wh
at
kin
ds
of
sym
pto
ms
wo
uld
ari
se
as
a c
on
seq
uen
ce?
As d
escribed in Section 7.6, a p
ulse is the p
ressure
wave
cre
ate
d d
uring each card
iac cycle as the b
ody’s elastic
arteries expand and then recoil. Common p
ulse p
oints—places
where
an artery
lies close to the b
ody surface—include the inside o
f th
e
wrist, w
here
the radial artery
travels, and the caro
tid artery
at th
e fro
nt
of th
e neck. Monitoring your pulse is an easy w
ay to o
bserv
e how a
change in your postu
re o
r activity affects your heart rate
.
To take your pulse, sim
ply p
ress your fingers o
n a p
ulse p
oint and
count th
e number of “b
eats” during o
ne m
inute
. For th
is exercise, ta
ke
your first measure
ment after you’ve b
een lying d
own for a few m
inute
s. If
you are
a healthy adult, it’s likely that your re
sting p
ulse w
ill be b
etw
een
65 and 70 b
eats p
er minute
. Now sit up, and take your pulse again. Did
the change in p
ostu
re correlate
with a change in your pulse? N
ow run in
place for 30 seconds and take your pulse rate
once again. In a short
para
gra
ph, describe w
hat changes in your heart’s activity led to the
pulse d
iffere
nces.
EXPLORE ON YOUR OWN
4.
Th
e h
igh
ly p
ub
lici
zed
dea
ths
of
sev
era
l a
irli
ne
tra
vel
ers
led
to
wa
rnin
gs
ab
ou
t “
eco
no
my
-cla
sssy
nd
rom
e.”
Th
e id
ea i
s th
at
eco
no
my
-cla
ssp
ass
eng
ers
do
n’t
ha
ve
as
mu
ch l
eg r
oo
m a
sp
ass
eng
ers
in m
ore
co
stly
sea
tin
g,
so t
hey
are
mo
reli
kel
y t
o s
it e
ssen
tia
lly
mo
tio
nle
ss f
or
lon
g p
erio
ds
on
fli
gh
ts—
con
dit
ion
s th
at
ma
y a
llo
w b
loo
d t
o p
oo
la
nd
clo
ts t
o f
orm
in
th
e le
gs.
Th
is c
on
dit
ion
is
call
edd
eep
-vei
n t
hro
mb
osi
s, o
r D
VT
. In
ad
dit
ion
, lo
wo
xy
gen
lev
els
in a
irp
lan
e ca
bin
s m
ay
in
crea
se c
lott
ing
.If
a c
lot
get
s la
rge
eno
ug
h t
o b
lock
blo
od
flo
w o
rb
rea
ks
free
an
d i
s ca
rrie
d t
o t
he
lun
gs
or
bra
in,
it c
an
leth
all
y b
lock
an
art
ery.
T
her
e co
uld
be
a t
ime
lag
bet
wee
n w
hen
a c
lot
form
s a
nd
hea
lth
pro
ble
ms,
so
an
air
tra
vel
er w
ho
late
r d
evel
op
s D
VT
mig
ht
easi
ly o
ver
loo
k t
he
po
ssib
le c
on
nec
tio
n w
ith
a f
lig
ht.
Stu
die
s a
re n
ow
un
der
wa
y t
o d
eter
min
e w
het
her
eco
no
my
-cla
sstr
av
el r
epre
sen
ts a
sig
nif
ica
nt
risk
of
DV
T.
Giv
enw
ha
t y
ou
kn
ow
ab
ou
t b
loo
d f
low
in
th
e v
ein
s,ex
pla
in w
hy
per
iod
ica
lly
get
tin
g u
p a
nd
mo
vin
ga
rou
nd
in
th
e p
lan
e’s
cab
in d
uri
ng
a l
on
g f
lig
ht
ma
y l
ow
er t
he
risk
th
at
a c
lot
wil
l fo
rm.
