Anatomy of the Heart
Kirsten Bazemore
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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 medicstinum
 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
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 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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Function of the AV Valves
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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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Function of the Semilunar Valves
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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 hear 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)
• Cyroperserved valves from human cadavers
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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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Therapeutic Relevance
Medical management
Percutaneous coronary
intervention (PCI)
Surgery (CABG)
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Cardiac Muscle Cell
Characteristics
 Striated
 Involuntary control
 Short, fat branched, and
interconnected
 One to two large, centrally
located nuclei
Cardiac Muscle Cell
 Adjacent cardiac cells
interlock at
intercalated discs
 Desmosomes
(prevents cell
separation during
contraction)
 Gap junctions (allow
cells to chemically
communicate)
 Mitochondria account
for 25-35% of volume
of cardiac cells 
highly resistant to fatigue
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Cardiac Muscle Cell
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T-Tubules
• Transverse to the surface
• Increases surface area
• Allows Extracellular Ca2+ ions to cross the membrane into the cell
Sarcoplasmic Reticulum
• Contains a supply of Ca2+ ions
• Extracellular Ca2+ binds to its receptors --> SR releases its own Ca2+ ions
(Extracellular Ca2+  SR  Ca2+ )
Sarcomere
Sarcomere: smallest contractile unit of a muscle (the region between
two Z-lines)





Thick filament = Myosin
Thin filament = Actin
A band = length of the myosin filament
Distance between Z line and H zone = length of actin filament
Length of actin and myosin filament does not change during
contraction
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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.
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QUESTIONS?
Physiology of the Heart
Kirsten Bazemore
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Types of Cardiac Muscle
Cells
Contractile Cells
• 99% of cardiac muscle cells
• Do mechanical work of pumping
• Normally do not produce action potentials
Autorhythmic Cells
• 1% or cardiac muscle cell
• Do not contract
• Generate and conduct action potentials
• Unstable membrane potential (never rests,
continues depolarization)
Action Potential of Contractile Cells
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Contraction in Contractile Cells
Transmission of
depolarization
from Na+ ions
channels
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11. Cross Bridge Formation. Energized
myosin head attached to an action
myofilament, forming a cross bridge.
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4. Cocking of the myosin head. As
the ATP is hydrolyzed to ADP and Pi,
the myosin head returns to its
prestroke high-energy, or “cocked,”
position.
2. The power (working stroke). ADP
and Pi are released and the myosin
head pivots and bends, changing to
its bent low-energy state. As a result it
pulls the action filament toward the M
line.
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3. Cross bridge detachment. After ATP
attaches to myosin, the link between
myosin and actin weakens, and the
myosin head detaches (the cross
bridge “breaks”).
*This cycle will continue as long
as ATP is available and Ca2+ is
bound to troponin.
Contraction in Contractile Cells
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Intrinsic Cardiac Conduction
System (autorhythmic cells)
The intrinsic cardiac conduction system consist of noncontractile cardiac cells
specialized to initiate and distribute impulses throughout the heart, so that is
depolarizes and contracts in an orderly, sequential manner.
Action Potentials of Pacemaker Cells
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Where Are Pacemaker Cells
Found?
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Sequence of Excitation Pacemaker Cells
1. SA Node
• Generates ~75 times/min
• Sets pace for the heart
• Faster depolarization rate
(considered heart’s pacemaker)
• It rhythm, sinus rhythm, determines
the heart rate
2. AV Node
•
Delays impulse for 0.1 s to allow
the atria to respond and complete
their contraction before the
ventricles contract
3./4. AV Bundle/ Bundle brances
• Since the atria and ventricles are
not connected by gap junctions,
the AV bundle is the only electrical
connection between them
• The bundles branches into 2
directions along the interventricular
septum toward the apex
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Sequence of Excitation Pacemaker Cells
5. Subendocardinal Conducting
Network
• also called Purkinje fibers
• Excites the septal cells
• More elaborate on the left
ventricle since it is much
larger than the right side of
the heart
*Slower pacemakers can dominate
when the faster pacemakers stop
functioning.
Homeostatic Imbalance
• Arrhythmias
• Uncoordinated atrial and
ventricular contractions
• Fibrillations
• Heart block
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Electrocardiography (EKG/ECG)
Electrocardiogram (EKG)
• Recording of heart
electrical activities
Electrocardiograph
• Device that records
electrical current of heart
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Sequence of EKG Events
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What’s wrong with the EKG?
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Elevated ST wave
The Cardiac Cycle
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The heart undergoes some dramatic writhing movements as it
alternately contracts, forcing blood out of its chambers, and then
relaxes, allowing its chambers to refill with blood.
Systole
•Emptying of ventricles
Diastole
•Filling of ventricles
Heart Sounds
Lub
•Closing of AV valves
Dub
•Closing of SL valves
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Cardiac Output (CO)
Cardiac output (C) is the amount of blood that is pumped out
by each ventricle is 1 minute.
The equation to calculate CO is shown below.
CO = HR X SV
The average adult cardiac output is ~ 5 mL. (equation shown
below using the normal resting values for HR and SV)
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Cardiac Output (CO)
Cardiac output (C) is the amount of blood that is pumped out
by each ventricle is 1 minute.
The equation to calculate CO is shown below.
CO = HR X SV
The average adult cardiac output is ~ 5 mL. (equation shown
below using the normal resting values for HR and SV)
Cardiac Output (CO)
Cardiac output is highly variable and increases markedly in
response to special demands.
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Homeostatic Imbalance of
Heart Rate
Tachycardia: an abnormally fast heart rate (more than 100 beats/min)
that may result from elevated body temperature, stress, certain drugs, or heart
disease.
• Persistent tachycardia is considered pathological because
tachycardia occasionally promotes fibrillation.
Bradycardia: a heart rate slower than 60 beats/min. It may result from
low body temperature, certain drugs, or parasympathetic nervous activation.
• In poorly conditioned people, persistent bradycardia may result in
grossly inadequate blood circulation to body tissues.
It is a known, and desirable, consequence of endurance training.
With physical and cardiovascular conditioning, the heart hypertrophies and
SV increases, allowing a lower resting heart rate while still providing the
same cardiac output.
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Stroke volume (SV) represents the difference between end
diastolic volume (EDV), the amount of blood that collects in a
ventricle during diastole, and end systolic volume (ESV), the
volume of blood remaining in a ventricle after it has contracted.
Formula for Stroke volume:
Although many factors affect SV by altering EDV or ESV, the
three most important are preload (EDV), contractility, and
afterload (ESV).
Preload & Afterload
Preload
• Amount of blood returning to RA
• the load, or stretch, put on the ventricle by the amount of
entering blood volume.
• The ventricle will tolerate only so much volume before the
ventricle is stretched too far and thus reduces stroke volume.
Afterload
• Force against which ventricles have to pump to eject blood
• one can still have a normal cardiac function but have an
afterload that negatively affects stroke volume
Therapeutic Significance
Preload reducers
• Venodilators (nitroglycerin)
• Cause peripheral edema, HA
(headache)
Afterload reducers
• Arterial vasodilators (hydralazine)
• cause Reflex tachycardia
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Homeostatic Imbalance of
Cardiac Output
In congestive heart failure (CHF), the heart is such an inefficient
pump that blood circulation is inadequate to meet tissue
needs. The disorder reflects weakening of the myocardium.
Certain conditions that the myocardium include:
• Coronary atherosclerosis
• Multiple myocardial infarctions
• Dilated cardiomyopathy (DCM)
In peripheral congestion the right side of the heart fails  stagnate blood in
body organs and pooled fluid in tissue  impair cells due to a lack on
nutrients.
• Failure on one side can lead to heart failure and the heart become
irreparable.
Treatment: use diuretics, reduce afterload (reduce pressure), heart transplants
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QUESTIONS?
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Additional Help
 Contact Info:
 kbazemore12@gmail.com
Layers of the Heart: https://www.khanacademy.org/science/health-andmedicine/circulatory-system/circulatory-system-introduction/v/layers-of-the-heart
Flow of blood: https://www.youtube.com/watch?v=7XaftdE_h60
Normal sinus rhythm of EKG: https://www.youtube.com/watch?v=lRHq7sMRWpU
Heart cells/Heart contraction: https://www.youtube.com/watch?v=__afuK1CMpQ