Anatomy & physiology
of the heart
Heart Anatomy
 Size, Location, and Orientation
 Enclosed in the mediastinum
 Base (posteriorsuperior portion) and
Apex (inferioranterior portion)
Heart Anatomy
 Coverings

Pericardium
 protects the heart
 anchors the heart to surrounding
structures such as the diaphragm and
the great vessels
 prevents overfilling of the heart with
blood
Heart Anatomy
 Coverings
 pericardial cavity contains a film of serous
fluid
 pericarditis: inflammation of the
pericardium which may lead to adhesions
between the layers or the buildup of fluid in
the pericardial cavity (cardiac tamponade)
Heart Anatomy
 Heart Wall
 Epicardium
 Myocardium

bulk of the heart consisting mainly of
cardiac muscle
Heart Anatomy
 Heart Wall
 Endocardium

simple squamous epithelium and a thin
CT layer that lines the heart chambers
and valves and is continuous with the
endothelial lining of the blood vessels
Heart Anatomy
 Chambers
 Atria
 Features
 small, thin-walled chambers
 Functions
 receiving chambers for blood returning
to the heart from the circulation
 push the blood into the adjacent
ventricles.
Heart Anatomy
 Chambers
 Atria
 Receive blood from
 right side
 Superior and Inferior Vena Cava
 Coronary Sinus (draining the
myocardium)
 left side
 Pulmonary Veins
Heart Anatomy
 Chambers
 Ventricles
 Features
 make up most of the mass of the heart
 the walls of the left ventricle are 3X
thicker than those of the right
Heart Anatomy
 Chambers
 Ventricles
 Functions
discharging chambers of the heart
propel blood to Pulmonary Trunk (right ventricle), Aorta
(left ventricle)
Heart Anatomy
 Pathway of Blood Through the Heart
 Pulmonary Circuit
 functions strictly as gas exchange
 the right side of the heart is the pulmonary
circuit pump

this is a short, low-pressure circuit
Heart Anatomy
 Pathway of Blood Through the Heart

Systemic Circuit
o functions as both gas and nutrient
exchange
o the left side of the heart is the systemic
circuit pump
o this is a long, high-resistance pathway
through the entire body
Heart Anatomy
 Heart Valves
 These enforce the one-way flow of blood
through the heart
 The valves open and close in response to
differences in blood pressure on their two sides
Heart Anatomy
 Heart Valves
 Atrioventricular Valves
 the valves close when the ventricular
pressure increases and forces blood against
the valve flaps
 Tricuspid (right side)
 Bicuspid (Mitral) (left side)
Heart Anatomy

Heart Valves
 Semilunar Valves
located between the ventricles and the large
arteries
 these open when the pressure produced by
the contracting ventricle exceeds that in the
artery and close when the arterial pressure
exceeds the pressure produced by the
relaxing ventricle
 Pulmonary (right side)
 Aortic (left side)

Coronary Circulation
 Coronary Arteries
 the coronary arteries arise from the base of the
aorta and actively deliver blood only when the
heart is relaxed
 the heart is 0.5% of body weight and receives
5% of the body's blood supply (most to the left
ventricle)
Coronary Circulation
 Coronary Arteries
 left main coronary artery
 left anterior descending artery: serves the
interventricular septum and anterior walls of
both ventricles
 circumflex artery: serves the left atrium and
posterior wall of the left ventricle
Coronary Circulation
 Coronary Arteries
 Right main coronary artery
 posterior descending artery: serves the posterior
walls of both ventricles
 marginal artery: lateral wall of the right side of the
heart
 Cardiac Veins follow arteries and join at the
Coronary Sinus which empties blood into the right
atrium
Heart Physiology
 Electrical Events
 Intrinsic Conduction System of the Heart
 the ability of cardiac muscle to depolarize
and contract is intrinsic (no nervous
stimulation is required)
 nerve impulses can alter the basic rhythm of
heart activity set by intrinsic factors
Heart Physiology
 Electrical Events
 Action Potential Generated by Autorhythmic
Cells
 Sequence of Excitation
o Sinoatrial Node
o Atrioventricular Node
o Atrioventricular Bundle (bundle of His)
o Bundle Branches
o Purkinje Fibers
Heart Physiology
 Electrical Events
 Extrinsic Innervation of the Heart
 fibers of autonomic nervous system
accelerate or inhibit the basic rate of
heartbeat set by the intrinsic conduction
system
Heart Physiology
 Electrical Events
 Electrocardiography
 electrical currents generated and transmitted
through the heart spread throughout the
body and can be monitored
 the graphic recording of electrical changes
during heart activity is called an
electrocardiogram (ECG or EKG)
Heart Physiology
 Electrical Events
 Electrocardiography
 the ECG consists of series of three waves
o P Wave: atrial depolarization starting at the
SA node
o QRS Complex: ventricular depolarization
Heart Physiology
 Electrical Events
 Electrocardiography
o P-R (P-Q) interval: time from the
beginning of atrial excitation to the
beginning of ventricular excitation and
includes the contraction of the atria and
the passage of the depolarization wave
through the rest of the conduction system
Heart Physiology
 Electrical Events
 Electrocardiography
o T Wave: ventricular repolarization
o Q-T interval: time from the beginning of the
ventricular depolarization through their
repolarization and includes the contraction of
the ventricles
Heart Physiology

Mechanical Events: The Cardiac Cycle
 Terms
Systole: contraction period of heart activity
 Diastole: relaxation period of heart activity

Heart Physiology
 Mechanical Events: The Cardiac Cycle
 Cardiac Cycle
o pressure in the heart is low and the blood
is returning passively (70% of ventricle
filling occurs)
o atria depolarize (P wave) and contract
and force the remaining 30% of the blood
into the ventricles
o the atria relax and remain in diastole
through the rest of the cycle
Heart Physiology
 Mechanical Events: The Cardiac Cycle
o the ventricles depolarize (QRS complex)
o ventricles begin their contraction
o ventricular pressure rises rapidly and the
AV valves close
o as ventricular pressure rises above arterial
pressure the semilunar valves open and
the ventricles empty during the
ventricular ejection phase
Heart Physiology
 Mechanical Events: The Cardiac Cycle
o ventricular systole ends with the
repolarization of the ventricles (T wave)
o ventricles relax and ventricular pressure
drops
o semilunar valves close
o the atria have been filling with blood since
ventricular systole and when the atrial
pressure exceeds the ventricular pressure the
AV valves open ventricular filling begins
again
Heart Physiology
 Cardiac Output
 General
 cardiac output is the amount of blood
pumped out by each ventricle in 1 minute
and is the product of heart rate (HR) and
stroke volume (SV)
 stroke volume is the volume of blood
pumped out by one ventricle with each beat
and is the difference between end diastolic
volume (EDV) and the end systolic volume
(ESV)
Heart Physiology
 Cardiac Output
 Regulation of Stroke Volume
 Preload: Degree of Stretch
 affected by the EDV and operates
intrinsically
 Frank Starling Law of the Heart: The
greater the degree of stretch of cardiac
muscle fibers the greater the force of
contraction and the greater the stoke
volume
Heart Physiology
 Cardiac Output
 resting cardiac fibers are normally shorter
than the optimal length and stretching
them (increasing EDV) produces dramatic
increases in contractile force
 anything that increases the volume or
speed of venous return (slow heart rate
or exercise) increases EDV which
increases the force of contraction which
increases stroke volume
Heart Physiology
 Cardiac Output
 Contractility
 affects the ESV and are extrinsic factors
that increase the contractile strength of
heart muscle
 many chemicals enhance contractility
(positive inotropic agents)
Heart Physiology
 Cardiac Output
 Afterload: Back Pressure
 affects the ESV
 the pressure exerted on the aortic (80
mm Hg) and pulmonary (20 mm Hg)
valves by arterial blood
 important in people with hypertension
where ESV is increased and stroke
volume is reduced
SA
AV