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Anatomy of the Heart
KayOnda Bayo
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2 Circuits
Pulmonary
•Heart lungs  heart
Systemic
•Heart  body  heart
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The heart=a muscular double pump with 2 functions
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Overview
 The right side receives
oxygen-poor blood from
the body and tissues and
then pumps it to the lungs
to pick up oxygen and
dispel carbon dioxide
 Its left side receives
oxygenated blood
returning from the lungs
and pumps this blood
throughout the body to
supply oxygen and
nutrients to the body
tissues
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Arteries
• Carry blood away from heart
• Except pulmonary arteries (carries
deoxygenated blood)
Veins
• Carry blood to heart
• Except pulmonary veins (carries
oxygenated blood)
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simplified…
 Cone shaped muscle
 Four chambers
 Two atria, two ventricles
 Double pump – the ventricles
 Two circulations
 Systemic circuit: blood vessels that transport blood to and
from all the body tissues
 Pulmonary circuit: blood vessels that carry blood to and from
the lungs
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Heart’s position in thorax
Heart’s position in thorax
In mediastinum – behind sternum and
pointing left, lying on the diaphragm
It weighs 250-350 gm (about 1 pound)
Feel your heart beat at apex
(this is of a person lying down)
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Coverings of the Heart
Fibrous Pericardium
Visceral Layer
Parietal Layer
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Layers of the Heart
Pericardium
Myocardium
Endocardium
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 Pericardium (double-walled sac)
 Protects against infection
 Provides lubrication to the heart
 Fixes the heat to the mediastinum
 Myocardium
 Middle layer
 Contains many capillaries & nerve
endings
 Has cardiac muscle forming the bulk of
the heart – thickest layer
 Layer that contracts
 Endocardium
 Has an endothelial layer that lines the
heart chambers
 Contains Perkinje fibers (specialized
nerve fibers used during the heart beat)
How Pericardium is Formed
Around the Heart
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Pericardial Cavity
 Between the parietal and visceral layer of the serous pericardium
 Contains serous fluid  lubricates membranes to reduce friction
 *Pericarditis: inflammation of the pericardium that roughens the
serous membrane surface
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 The Heart is enclosed within a
double-walled sac called the
pericardium.
 Consists of 2 layers

Fibrous pericardium

Serous pericardium
 Fibrous pericardium:

Composed of dense connective
tissue (protects the heart)

Anchors to surrounding walls

Prevents the heart from overfilling
with blood
 Serous pericardium
 Located deep to fibrous
pericardium
 Contains 2 layers  function to
lubricate the heart to prevent
friction during activity
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Heart Chambers
 There are 4 chambers in the
heart
 2 superior ventricles
 2 inferior atria
 Atriums known as the
receiving chamber
 Ventricles known as the
discharging chambers
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Chambers of the heart
sides are labeled in reference to the
patient facing you
 Two atria
 Right atrium
 Left atrium
--------------------------------------------------------------------------------
 Two ventricles
 Right ventricle
 Left ventricle
Chambers of the heart
divided by septae:
 Two atria-divided by
interatrial septum
 Right atrium
 Left atrium
 Two ventricles-divided by
interrventricular septum
 Right ventricle
 Left ventricle
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Relative thickness of muscular walls
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LV thicker than RV because it forces blood out against more resistance; the
systemic circulation is much longer than the pulmonary circulation
Atria are thin because ventricular filling is done by gravity, requiring little
atrial effort
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Pectinate
muscles
Auricle
Atria
+Fossa ovalis
+Foramen
ovale
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The Fossa Ovalis is an embryonic remnant of the
foramen ovale, which normally closes after birth.
Following birth, the foramen ovale is covered by
a fibrous sheet. Failure of the foramen ovale to
close results in a disorder called patent foramen
ovale.
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Trabecular
carneae
Chordae
tendineae
Ventricles
Papillary
muscles
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Heart Valves:
Atrioventricular (AV) Valves
 Prevent backflow into the atria when the ventricles contract
 Both valves contains 3 cusps
 Tricuspid valve (right AV valve) has 3 flexible cusps
 Mitral valve (left AV valve) has 2 cusps a.k.a. “bicuspid valve”
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Heart Valves:
Semilunar (AV) Valves
 Prevent backflow into associated ventricles
 Aortic valve protects the orifice between the left
ventricle and the aorta
 Pulmonary valve guards the orifice between the
right ventricle and the pulmonary artery
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Homeostatic Imbalance of
Heart Valves
Heart valves can function with “leaky” valves as long as the impairment is not
too severe. Severe valve deformities can seriously hamper cardiac function.
Problems with Valves:
 An incompetent valve forces the heart to pump the same blood over and
over because the valve does not close properly.
 When stenosis occurs, the valve flaps become stiff and constrict the
opening heart contracts more than normal
In both conditions, the heart’s workload increases  weakens the heart
overtime
Treatment: Heart valve is replaced with:
• Mechanical Heart
• Pig or cow valve (chemically treated to reduce rejection)
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Blood Return to R-atrium
Superior vena cava (SVC)
Inferior vena cava (IVC)
Coronary sinus (CS)
Pathway of Blood Through
the Heart
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Pathway of Blood (cont.)
Superior
vena cava,
Inferior
vena cava,
Coronary
sinus
Left
Ventricle
Right
Atrium
Mitral
Valve
Left
Atrium
Aortic
Semilunar
valve
Aorta
Rest of
the Body
Tricuspid
valve
Right
Ventricl
e
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Pulmonary
Semilunar
valve
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pulmonary
veins
Pulmonary
Artery &
Trunk
Lungs
Coronary Artery Circulation
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Even though the heart is filled
with blood, the blood provides
little nourishment to the heart
(the myocardium tissue is too
thick). Blood is supplied to the
heart via Coronary Circulation
which is the shortest circulation
in the body.
Branching of Coronary Arteries
Right Coronary Artery (RCA)
 Branches into:
 Right marginal artery
 Posterior descending artery
 Supplies:
 Right atrium
 Bottom portion of both
ventricles and back of
septum
 Together the RCA and its
branches supply the R. Atrium
and nearly all the ventricles.
Left Coronary Artery
(Left Main Trunk)
 Branches into:
 Circumflex artery
 Anterior interventricular
artery
 Supplies:
 Circumflex Artery: left
atrium, side and back of
the left ventricle
 Anterior interventricular
artery: front and bottom of
the left ventricle and front
of the septum
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*What happens when a
coronary artery is blocked?
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 Angina Pectoris
 Myocardial
Infarction (MI)
Homeostatic Imbalance of
Coronary Blood Flow
Partial blockade
• Decreased blood flow  ischemia 
angina
• Treatment:????
Complete blockade
• No blood flow  myocardial infarction
• Treatment: ?????
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Cardiac Muscle Cell
Characteristics
 Striated
 Involuntary control
 Short, fat branched, and
interconnected
 One to two large, centrally
located nuclei
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Unique Characteristic of the
Heart
 Some cardiac fibers are auto-rhythmic. These fibers have the
ability to depolarize spontaneously and pace the heart.
 The bulk of the heart consists of contractile muscle cells that are
responsible for the heart’s pumping activity.
 All cells of the heart MUST contract as a unit or the heart
doesn’t contract at all.
 Gap junctions electrically tie all cardiac muscle together into a
single contractile unit.
Physiology of the Heart
KayOnda Bayo
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Contractile Cell Action
Potential
 Four phases of action potential
 Resting membrane potential -90 mV
 Depolarization due to fast Na+ channels
 Plateau due to slow Ca2+ channels
 Repolarization due to K+ channels
Action
potential
Plateau
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2
0
Tension
development
(contraction)
–20
–40
3
1
–60
Absolute
refractory
period
–80
0
150(ms)
Time
300
Tension (g)
Membrane potential (mV)
Contractile Cell A.P.
1 Depolarization is due to Na+
influx through fast voltage-gated Na+
channels. A positive feedback cycle
rapidly opens many Na+ channels,
reversing the membrane potential.
Channel inactivation ends this phase.
2 Plateau phase is due to Ca2+
influx through slow Ca2+ channels.
This keeps the cell depolarized
because few K+ channels are open.
3 Repolarization is due to Ca2+
channels inactivating and K+
channels opening. This allows K+
efflux, which brings the membrane
potential back to its resting voltage.
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Education, Inc.
Pacemaker Action Potential
 Present in SA & AV node
 Contains three phases
 Slow depolarization
 Unstable resting membrane potential
 Between -60 mV to -40 mV
Pacemaker (Autorhythmic)
Cells
 Unstable resting membrane potentials
(pacemaker potentials)
 opening of slow Na+ channels
 Continuously depolarize
 At threshold, Ca2+ channels open
 Explosive Ca2+ influx
 rising phase of A.P.
 Repolarization
 inactivation of Ca2+ channels
 opening of voltage-gated
K+ channels
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Education, Inc.
Pacemaker Action Potential
 Three phases of action potential:
 Pacemaker potential
 Repolarization
 closes K+ channels
 opens slow Na+ channels  ion imbalance
 Depolarization
 Ca2+ channels open  huge influx  rising phase
of A. P.
 Repolarization
 K+ channels open  efflux of K+
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Education, Inc.
Membrane potential (mV)
Pacemaker Action Potential
+10
0
–10
–20
–30
–40
–50
–60
–70
Action
potential
2
Threshold
2 Depolarization The action
potential begins when the
pacemaker potential reaches
threshold. Depolarization is due
to Ca2+ influx through Ca2+
channels.
2
3
3
1
1
Pacemaker
potential
Time (ms)
© 2013 Pearson Education, Inc.
1 Pacemaker potential This
slow depolarization is due to both
opening of Na+ channels and
closing of K+ channels. Notice
that the membrane potential is
never a flat line.
3 Repolarization is due to
Ca2+ channels inactivating and
K+ channels opening. This allows
K+ efflux, which brings the
membrane potential back to its
most negative voltage.
Sequence of Excitation
 Cardiac pacemaker cells pass impulses, in order,
across heart in ~220 ms
 Sinoatrial(SA) node 
 Atrioventricular(AV) node 
 Atrioventricular bundle 
 Right and left bundle branches 
 Subendocardial conducting network (Purkinje fibers)
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Education, Inc.
Heart Physiology: Sequence
of Excitation
 Sinoatrial (SA) node
 Pacemaker of heart in right atrial wall
 Depolarizes faster than rest of myocardium
 Generates impulses
 75X/minute (sinus rhythm)
 Inherent rate of 100X/minute
 Tempered by extrinsic factors
 Impulse spreads across atria, and to AV node
© 2013 Pearson
Education, Inc.
Figure 18.15a Intrinsic cardiac conduction system and action potential succession during one heartbeat.
Superior vena cava
Right atrium
1 The sinoatrial (SA)
node (pacemaker)
generates impulses.
Internodal pathway
2 The impulses
pause (0.1 s) at the
atrioventricular
(AV) node.
3 The
atrioventricular
(AV) bundle
connects the atria
to the ventricles.
4 The bundle branches
conduct the impulses
through the
interventricular septum.
Left atrium
Subendocardial
conducting
network
(Purkinje fibers)
Interventricular
septum
5 The subendocardial
conducting network
depolarizes the contractile
cells of both ventricles.
Anatomy of the intrinsic conduction system showing the sequence of
electrical excitation
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Education, Inc.
Heart Sounds
 Two sounds (lub-dup) associated with closing of
heart valves
 First as AV valves close; beginning of systole ”lub”
 S1
 Tricuspid & Bicuspid(Mitral) Valves
 Second as SL valves close; beginning of ventricular
diastole “dup”
 S2
 Aortic & PulmonaryValves
 Pause indicates heart relaxation
 Heart murmurs - abnormal heart sounds; usually
indicate incompetent valves
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Education, Inc.
Figure 18.20 Areas of the thoracic surface where the sounds of individual valves can best be detected.
Aortic valve sounds
heard in 2nd intercostal
space at right sternal
margin. S2
Pulmonary valve
sounds heard in 2nd
intercostal space at left
sternal margin. S2
Mitral valve sounds
heard over heart apex
(in 5th intercostal space)
in line with middle of
clavicle. S1
Tricuspid valve sounds
typically heard in right
sternal margin of 5th
intercostal space. S1
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Education, Inc.
Heart Sounds
 Two sounds associated with filling of
ventricles(Inaudible)
 Rapid flow of blood from atria into ventricles
 S3
 Normally heard in children
 Heard in adults associated with disease
 Inflow of blood into ventricles during atrial systole
 S4
 Heard in disease state such as diastolic stiffness or
high atrial pressure
Cardiac Output (CO)
 Volume of blood pumped by each ventricle in
one minute
 CO = heart rate (HR) × stroke volume (SV)
 HR = number of beats per minute
 SV = volume of blood pumped out by one ventricle
with each beat
 Normal – 5.25 L/min
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Education, Inc.
Cardiac Output (CO)
 At rest
 CO (ml/min) = HR (75 beats/min)  SV (70
ml/beat)
= 5.25 L/min
 CO increases if either/both SV or HR
increased
 Maximal CO is 4–5 times resting CO in
nonathletic people
 Maximal CO may reach 35 L/min in trained
athletes
 Cardiac reserve - difference between
resting and maximal CO
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Education, Inc.
Regulation of Stroke Volume
 SV = EDV – ESV
 EDV affected by length of ventricular diastole and
venous pressure
 ESV affected by arterial BP and force of ventricular
contraction
 Three main factors affect SV:
 Preload
 Contractility
 Afterload
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Education, Inc.
Homeostatic Imbalance
 Hypocalcemia  depresses heart
 Hypercalcemia  increased HR and contractility
 Hyperkalemia  alters electrical activity  heart
block and cardiac arrest
 Hypokalemia  feeble heartbeat; arrhythmias
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Education, Inc.
Homeostatic Imbalances
 Tachycardia - abnormally fast heart rate
(>100 beats/min)
 If persistent, may lead to fibrillation
 Bradycardia - heart rate slower than
60 beats/min
 May result in grossly inadequate blood circulation in
nonathletes
 May be desirable result of endurance training
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Education, Inc.
Factors that Influence Heart
Rate
 Age
 Fetus has fastest HR
 Gender
 Females faster than males
 Exercise
 Increases HR
 Body temperature
 Increases with increased temperature
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Education, Inc.
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QUESTIONS?