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The Cardiovascular
System
The anterior surface of the heart
demonstrates an opened left
anterior descending coronary
artery.Within the lumen of the
coronary can be seen a dark red
recent coronary thrombosis. The
dull red color to the myocardium
as seen below the glistening
epicardium to the lower right of
the thrombus is consistent with
underlying myocardial infarction.
The Cardiovascular System

A closed system of the heart and blood
vessels
– The heart pumps blood
– Blood vessels allow blood to circulate to all
parts of the body

The function of the cardiovascular system
is to deliver oxygen and nutrients and to
remove carbon dioxide and other waste
products
The Heart
 Location
–Thorax between the lungs
–Pointed apex directed toward
left hip
 About the size of your fist
The Heart
Figure 11.1

Gross photograph of normal lungs and
heart. The pleural surface is smooth
and shiny. The lungs extend down to
the apex of the heart.
The Heart: Coverings
 Pericardium
membrane
– a double serous
– Visceral pericardium
 Next to heart
– Parietal pericardium
 Outside layer
 Serous
fluid fills the space
between the layers of
pericardium
The Heart: Heart Wall
 Three
layers
–Epicardium
 Outside layer
 This layer is the parietal pericardium
 Connective tissue layer
–Myocardium
 Middle layer
 Mostly cardiac muscle
–Endocardium
 Inner layer
 Endothelium
Dark area
shows
beginning
healing –
increased
blood
supply
Acute Myocardial Infarction
LightColored
Tissue
indicates a
myocardial
infarction
Normal
Fatty
Tissue
Heart Cross Section
Old Myocardial Infarctions
Scar tissue from
an infarct at
least two weeks
old.
External Heart Anatomy
Figure 11.2a
The Heart: Chambers
Right and left side act as
separate pumps
 Four chambers

– Atria
 Receiving chambers
– Right atrium
– Left atrium
– Ventricles
 Discharging chambers
– Right ventricle
– Left ventricle
Figure 11.2c
Blood Circulation
Figure 11.3
The Heart: Valves
 Allow
blood to flow in one direction
 Four valves
–Atrioventricular valves – between atria and
ventricles
 Bicuspid/MITRAL valve (left)—2 flaps or
cusps…only heart valve with 2 cusps
 Tricuspid valve (right)—3 flaps or cusps
–Semilunar valves between ventricle and artery
 Pulmonary semilunar valve
 Aortic semilunar valve
Tricuspid valve
Chordae
Tendinae
Papillary
Muscles
This is the tricuspid valve. The leaflets are thin
and delicate. Just like the mitral valve, the leaflets
have thin chordae tendinae that attach the leaflet
margins to the papillary muscles of the ventricular
wall below.
The Heart: Valves
 Valves
open as blood is pumped
through
 Held in place by chordae tendineae
(“heart strings”)
 AV valves close when ventricles
contract, to prevent backflow in
Atria….backflow = “valvular
prolapse”
Operation of Heart Valves
Figure 11.4
The Heart: Associated Great
Vessels
 Aorta
– Leaves left ventricle
 Pulmonary
arteries
– Leave right ventricle
 Vena
cava
– Enters right atrium
 Pulmonary
veins (four)
– Enter left atrium
These three aortas demonstrate mild, moderate, and severe
atherosclerosis from bottom to top. At the bottom, the mild
atherosclerosis shows only scattered lipid plaques. The aorta
in the middle shows many more larger plaques. The severe
atherosclerosis in the aorta at the top shows extensive
ulceration in the plaques.
Aortic Aneurysm
Here is an example of an
atherosclerotic aneurysm of the aorta
in which a large "bulge" appears just
above the aortic bifurcation. Such
aneurysms are prone to rupture when
they reach about 6 to 7 cm in size.
They may be felt on physical
examination as a pulsatile mass in the
abdomen. Most such aneurysms are
conveniently located below the renal
arteries so that surgical resection can
be performed with placement of a
dacron graft.
External Heart Anatomy
Figure 11.2a
Coronary Circulation
 Blood
INSIDE the heart chambers
does not nourish the myocardium
 The heart has its own nourishing
circulatory system
– Coronary arteries
– Cardiac veins
– Blood empties from the cardiac veins
into the right atrium via the coronary
sinus
Coronary Arteries
This is a normal coronary artery. The lumen is large,
without any narrowing by atheromatous plaque. The
muscular arterial wall is of normal proportion. If there is
narrowing, bypass surgery may be required.
The Heart: Conduction System
Intrinsic
conduction system
(nodal system)
–Heart muscle cells are
depolarized in one direction
only, from atria to ventricles
–Enforces a contraction rate of
75 BPM
The Heart: Conduction System
Special
tissue sets the pace
Sinoatrial node—starts each beat
–Pacemaker
Thru atria to Atrioventricular node
Quickly thru Atrioventricular
bundle (His)
Bundle branches
Purkinje fibers
Blood now ejected into large arts.
Heart Contractions
Figure 11.5
Conduction Problems
All contractions initiated by the
SA node
If SA node is damaged, slower
heart rate, pacemaker is
installed.
If AV node is damaged,
ventricles beat at own
rate=“heartblock”
Conduction Problems
Ischemia—lack
of blood supply
to the heart muscle
This can lead to
Fibrillation….uncoordinated
shuddering of the heart
muscle….”Bag of worms”
Use a “defibrillator” to correct
Defibrillator
QRS Complex
QRS Complex
3
recognizable waves
–P WAVE…depolarization of atria
immediately prior to contraction
–QRS complex…depolarization of the
ventricles
–T WAVE…repolarization of the
ventricles
Normal Heart Rhythm
Ventricular Fibrillation
Atrial Fibrillation
Filling of Heart Chambers – the
Cardiac Cycle
Figure 11.6
The Heart: Cardiac Cycle
Atria
contract simultaneously
Atria relax, then ventricles
contract
Systole = contraction
Diastole = relaxation
The Heart: Cardiac Cycle
 Cardiac
cycle – events of one
complete heart beat
–Mid-to-late diastole – blood flows
into ventricles
–Ventricular systole – blood pressure
builds before ventricle contracts,
pushing out blood
–Early diastole – atria finish re-filling,
ventricular pressure is low
The Heart: Cardiac Output
Cardiac
output (CO)
– Amount of blood pumped by each side of the
heart in one minute
– CO = (heart rate [HR]) x (stroke volume [SV])
Stroke
volume
– Volume of blood pumped by each ventricle in
one contraction
Cardiac Output Regulation
Figure 11.7
The Heart: Regulation of Heart
Rate

Stroke volume usually remains relatively
constant
– Starling’s law of the heart – the more that the
cardiac muscle is stretched, the stronger the
contraction

Changing heart rate is the most common
way to change cardiac output
The Heart: Regulation of Heart
Rate

Increased heart rate
– Sympathetic nervous system
 Crisis
 Low blood pressure
– Hormones
 Epinephrine
 Thyroxine
– Exercise
– Decreased blood volume
The Heart: Regulation of Heart
Rate

Decreased heart rate
– Parasympathetic nervous system
– High blood pressure or blood volume