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The Cardiovascular System: The Heart
• Heart pumps
over 1 million
gallons per year
• Over 60,000
miles of blood
vessels
Functions
• Transport oxygen & carbon dioxide to
and from tissues
• Transports nutrients, waste products,
and hormones
• Regulates body temperature
• Plays a role in the immune response
Important Facts
• A healthy adult heart pumps about 5
liters of blood out per minute.
• During vigorous exercise, the amount of
blood pumped out of the heart per
minute drastically increases.
• If the heart stops contracting, blood
flow throughout the body stops.
• If the heart stops functioning for a few
minutes life will end.
Circulation
• Heart is two pumps in one!!!
• Pulmonary —right side of heart forcing
blood to flow to the lungs and back to
the left side of the heart
• Systemic —left side of heart forces
blood to flow to all other tissues in the
body and back to the right side of the
heart
Size, Form, and Location of
Heart
• Shaped like a blunt cone
• About the size of a
closed fist
• In thoracic cavity
between the lungs
• Apex —blunt, rounded
point; most inferior part
of heart
• Base —larger, flat
portion; directed
superiorly and slightly
posteriorly
Anatomy of the Heart
• Pericardium —double
layered, closed sac
that surrounds the
heart
– Pericardial cavity —
space around the
heart
• Filled with a thin layer
of pericardial fluid—
helps reduce friction
as the heart moves
within the pericardial
sac
Layers of Heart Wall
• Epicardium
– visceral layer of
serous
pericardium
• Myocardium
– cardiac muscle
layer is the bulk
of the heart
• Endocardium
– chamber lining &
valves
Concept Check
• About how big is your heart? What is the
inferior portion called? The superior?
• How many miles of blood vessels does your
body contain?
• What are the two types of circulation the
heart does?
• What are the functions of the circulatory
system?
• What are the three layers of the heart?
• What surrounds the heart in the body?
Myocardial Thickness and Function
• Thickness of myocardium varies according to the function
of the chamber
• Atria are thin walled, deliver blood to adjacent ventricles
• Ventricle walls are much thicker and stronger
– right ventricle supplies blood to the lungs (little flow resistance)
– left ventricle wall is the thickest to supply systemic circulation
Thickness of Cardiac Walls
Myocardium of left ventricle is much thicker than the right.
External Anatomy of Heart
• Superior/Inferior Vena Cava —carry blood
from body to right atrium
• Pulmonary veins —carry blood from lungs to
left atrium
• Pulmonary arteries —carry blood from heart
to the lungs
• Aorta —carry blood from the heart to the
rest of the body
Heart Chambers
• Atria—2 upper chambers
– Receives blood from veins
– Contraction of atria forces blood into
ventricles
• Ventricle—2 lower chambers
– Pump blood out of the heart into arteries
– Left is thicker than right
Septum—separates heart into right and left
sections
Superior
Vena Cava
Aorta
Left atrium
Right atrium
Septum
Left ventricle
Right ventricle
Heart Valves
• Atrioventricular
valves—located between
atria and ventricles
– Prevent blood from
backflow into atrium
bicuspid
• Tricuspid valve—
between right atrium &
right ventricle
• Bicuspid (mitral) valve—
between left atrium &
left ventricle
tricuspid
Heart Valves
• Aortic semilunar
valve—blood flow
from left ventricle
to aorta
– Prevents backflow
• Pulmonary semilunar
valve—blood flow
from right ventricle
to pulmonary trunk
– Prevents backflow
Path of Blood Through Heart
• Enters through Superior/Inferior Vena
Cava—Right atrium—tricuspid valve—
Right ventricle—pulmonary semilunar
valve—pulmonary arteries—lungs—Left
atria—bicuspid valve—left ventricle—
aortic semilunar valve—aorta
Conduction System of Heart
• SA node
– cluster of cells in wall of Rt. Atria
– begins heart activity that spreads to both atria
– excitation spreads to AV node
• AV node
– in atrial septum, transmits signal to bundle of
His
• AV bundle of His
– the connection between atria and ventricles
– divides into bundle branches & purkinje fibers,
large diameter fibers that conduct signals
quickly
Electrocardiogram---ECG or EKG
• EKG
– Action potentials of all
active cells can be
detected and recorded
• P wave
– atrial depolarization
• P to Q interval
– conduction time from
atrial to ventricular
excitation
• QRS complex
– ventricular depolarization
• T wave
Conduction of the Heart
• Fibrillation—heart acting as a lot of
pacemakers causing the heart to contract
rapidly
– Reduces the output of the heart by only a few
milliliters of blood per minute when it occurs in the
ventricles—these needs to stop quickly before
death sets in
• Defibrillation—a strong electrical shock is
applied to the chest region
– Trying to cause heart to go back into normal
fibrillation
Auscultation
• Stethoscope
• Sounds of heartbeat are from turbulence
in blood flow caused by valve closure
– first heart sound (lubb) is created with the
closing of the atrioventricular valves
– second heart sound (dupp) is created with the
closing of semilunar valves
Blood Pressure
• Systole—contraction of the ventricles
– Atria are relaxed allowing blood to collect
– Immediately atrioventricular valves closes
– Once pressure builds beyond pressure in aorta and
pulmonary trunk, blood is forced into pulmonary
trunk and aorta
• Diastole—relaxation of the ventricles
– Atria contract allowing blood to flow into
ventricles
– Ventricular pressure decreases
– Semilunar valves close
Exercise and the Heart
• Sustained exercise increases oxygen
demand in muscles.
• Benefits of aerobic exercise (any activity
that works large body muscles for at least
20 minutes, preferably 3-5 times per week)
are;
–
–
–
–
–
increased cardiac output
increased HDL and decreased triglycerides
improved lung function
decreased blood pressure
weight control.
Congestive Heart Failure
• Causes of CHF
– coronary artery disease, hypertension, MI, valve
disorders, congenital defects
• Left side heart failure
– less effective pump so more blood remains in ventricle
– heart is overstretched & even more blood remains
– blood backs up into lungs as pulmonary edema
– suffocation & lack of oxygen to the tissues
• Right side failure
– fluid builds up in tissues as peripheral edema
Risk Factors for Heart
Disease
• Risk factors in heart disease:
–
–
–
–
high blood cholesterol level
high blood pressure
cigarette smoking
obesity & lack of regular exercise.
• Other factors include:
–
–
–
–
–
diabetes mellitus
genetic predisposition
male gender
high blood levels of fibrinogen
left ventricular hypertrophy
Coronary Artery Disease
• Heart muscle receiving
insufficient blood supply
– narrowing of vessels--atherosclerosis, artery
spasm or clot
– atherosclerosis-smooth muscle & fatty
deposits in walls of
arteries
• Treatment
– drugs, bypass graft,
angioplasty, stent
Clinical Problems
• MI = myocardial infarction
– death of area of heart muscle from lack of O2
– replaced with scar tissue
– results depend on size & location of damage
• Blood clot
– use clot dissolving drugs streptokinase or t-PA
& heparin
– balloon angioplasty
• Angina pectoris----heart pain from
ischemia of cardiac muscle
By-pass Graft
Stent in an Artery
• Maintains patency of blood vessel
Cardiac Cycle
• Repetitive pumping process that begins
with the onset of cardiac muscle
contraction and ends with the beginning
of the next contraction
• Pressure changes—Blood moves from
areas of high pressure to low pressure
• Blood Pressure
– Systole
– Diastole
Abnormal Heart Sounds
• Called murmurs
• Result of faulty valves—valve doesn’t
close tightly allowing blood to enter
• Makes a swishing sound immediately
after closure of the valve
– Example: incompetent bicuspid valve makes
a swishing sound after first heart sound
Regulation of Heart Function
• Cardiac output— volume of blood
pumped by either ventricle of the heart
each minute
– Cardiac output= stroke volume x heart rate
• Stroke volume— the volume of blood
pumped per ventricle each time the
heart contracts
• Heart rate— the number of times the
heart contracts each minute