Download The HEART - Model High School

4/22/2013
This muscle never stops working…
It works when you are asleep…
The HEART
It works when you eat…
It really works when you exercise….
What is it????
Heart
Facts
Hold out your hand and make a fist. If you're a
kid, your heart is about the same size as your
fist, and if you're an adult, it's about the same
size as two fists.
Your heart beats about 100,000 times in one
day and about 35 million times in a year. During
an average lifetime, the human heart will beat
more than 2.5 billion times.
Give a tennis ball a good, hard squeeze. You're using about the same
amount of force your heart uses to pump blood out to the body.
Even at rest, the muscles of the heart work hard--twice as hard as
the leg muscles of a person sprinting.
The human heart can create enough pressure that it could squirt blood
at a distance of thirty feet.
Located between the
lungs in the mid
thoracic region
Surrounded by a
membrane called the
pericardium
Apex points toward
the left hip
Composed of cardiac
muscle tissue
The chambers:
Left & Right Atria
Left & Right Ventricles
The vessels:
Pulmonary artery & vein
Superior & inferior vena cava
Aorta
The valves:
Atrioventricular valves = Tricuspid, Mitral,
Semilunar valves = Pulmonary & Aortic
Scientists have discovered that the longer the ring finger is in boys the
less chance they have of having a heart attack.
Pericardium
HEART
♥Membrane sac
♥Surrounds the heart
♥Protection
♥Anchors
♥Contains serous fluid
Pericarditis
inflammation of the
pericardium decreases
serous fluid causing painful
adhesions interfering with
heart movements
Pericardium
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The Valves
The Valves
Allow blood to flow in only one direction
Allow blood to flow in only one direction
The tricuspid valve separates the
right atrium and right ventricle
Composed of 3 flaps
The pulmonary semilunar valve
is the doorway between the right
ventricle and the pulmonary
artery which carries “dirty”
blood to the lungs
The mitral valve (sometimes called
the bicuspid valve) separates the
left atrium and left ventricle
Composed of 2 flaps
The aortic semilunar valve is the
doorway between the left
ventricle and the aorta which
carries “clean” blood to the body
Valves open as blood is pumped through
Held in place by chordae tendineae (“heart strings”)
Aorta
leaves left
ventricle
Pulmonary artery
leaves right
ventricle
Superior vena cava
enters right atrium
Rt Pulmonary veins
enters left atrium
L Pulmonary veins
enters left atrium
The Vessels
Superior Vena Cava
Inferior Vena Cava
Carry deoxygenated
blood from the upper
and lower parts of the
body into the heart
Pulmonary Arteries
Carry deoxygenated
blood from the heart
to the lungs
Pulmonary Veins
Carry oxygenated
blood from the
lungs to the heart
Aorta
Carries oxygenated
blood from the heart
out to the body
Inferior vena cava
enters right atrium
Cardiovascular System
A DOUBLE PUMP system
Pulmonary Circuit
RA  RV  Pulmonary artery  capillary beds of the alveoli
Systemic Circuit
capillary beds of the alveoli  LA  LV Aorta  Body
Functions to deliver oxygen
and nutrients and to
remove carbon dioxide and
other waste products
Oxygen-poor blood (shown in
blue) flows from the body into
the right atrium.
Blood flows through the
right atrium into the right
ventricle.
The right ventricle pumps
the blood to the lungs, where
the blood releases waste
gases and picks up oxygen.
The newly oxygen-rich blood
(shown in red) returns to the
heart and enters the left
atrium.
Blood flows through the left
atrium into the left ventricle.
The left ventricle pumps the
oxygen-rich blood to all parts
of the body.
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Lub Dub
The Heart’s
External Anatomy &
Conduction System
If you listen to
your heartbeat, it
makes a lub dub
sound.
The lub is when blood
is pushed out of the
heart into the body
and the dub is the
reloading of the heart
with more blood ready
to push it out to the
body
♥ Heart at rest
♥ Blood flows from large veins into atria
♥ Passive flow from atria into ventricles
♥ Atria (R & L) contract simultaneously
Pericardium
HEART
♥ Blood forced into ventricles
♥ Ventricles (R & L) contract simultaneously
♥ Atrioventricular valves close  “lub” sound
♥ Blood forced into large arteries
♥Membrane sac
♥Surrounds the heart
♥Protection
♥Anchors
♥Contains serous fluid
Pericarditis
inflammation of the
pericardium decreases
serous fluid causing painful
adhesions interfering with
heart movements
♥ Ventricles relax
♥ Semilunar valves close  “dub” sound
♥ Heart at rest
Pericardium
Heart Wall
♥ Epicardium (outside) – visceral layer
of the serous pericardium.
♥ Myocardium (muscle) – cardiac
muscle layer forming the bulk of the
heart.
♥ Endocardium (within) – endothelial
layer of the inner myocardial surface.
Cardiac Muscle
♥Specialized muscle cells
♥Involuntary
♥Striated
♥Cushioned by endomysium
♥Joined by intercalated discs
♥Cardiac cell metabolism
♥Areobic
♥Large mitochondria
♥Organic fuels: fatty acids & glucose
♥Fatigue resistance
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Coronary Arteries
Branch off aorta above aortic semilunar valve
Coronary Veins
♥ Left coronary artery
♥ supplies left atrium and
left ventricle
♥ Anterior interventricular
artery
♥ supplies both ventricles
♥ Right coronary artery
♥ supplies right ventricle
♥ Posterior interventricular
artery
♥ supplies both ventricles
The heart beats because of the spread
of electrical impulses to the heart
muscle, causing it to contract.
♥ Collects wastes from cardiac muscle
♥ Drains into a large sinus on posterior surface of
heart called the coronary sinus
♥ Coronary sinus empties into right atrium
Cardiac Conduction System
♥ Cardiac muscle tissue exhibits
autorhythmicity = generates its own
stimulation.
♥ This is possible because of an internal
cardiac conduction system which can
initiate and distribute electrical impulses.
Cardiac Conduction System
Sinoatrial (SA) Node
♥ Comprised of interconnected structures
♥ Sinoatrial node
♥ Atrioventricular node
♥ Atrioventricular Bundle
♥ Bundle Branches
♥ Purkinje Fibres
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Atrioventricular (AV) Node
Linked to the nervous system
♥ Junction of atria and ventricles
♥ Spread of depolarisation - from atrial
myocardium
♥ Delay 0.15 seconds
♥ Time atria to expel blood
♥ Time for ventricular filling
♥ Protection to ventricles
Atrioventricular
node
♥ Less autonomic nervous control than SA node
♥ Sympathetic ↑conduction time
♥ Parasympathetic ↓conduction time
Depolarization
Depolarization
The heart is autorhythmic
The heart is autorhythmic
♥ Depolarization begins
in sinoatrial (SA) node
♥ Spread through atrial myocardium
♥ Results in myocardial contration of the atria
♥ Delay in atrioventricular (AV) node
♥ To the Bundle of His
♥ AKA atrioventricular bundle
Electrocardiogram
Variations in electrical potential radiate
from the heart
ECG records electrical events in the heart.
♥ Separates into 2 main
branches left & right
♥ Located in the interventricular septum
♥ Left bundle – antero-superior division
♥ Right bundle – postero-inferior division
♥ Bundle branches divide - small, dense network
of conduction tissue called the Purkinje Fibers
Entire musculature depolarizes quickly
P wave
Depolarization of atria
Followed by contraction
P-P = one cardiac cycle
P-Q = time for atrial depolarization
Q-T = time for ventricular depolarization
T-P = time for relaxation
QRS complex
3 waves (Q, R, & S)
Depolarization of ventricles
Followed by contraction
T wave
Repolarization of ventricles
P-Q interval
Time atria depolarize & remain depolarized
Q-T interval
Time ventricles depolarize & remain depolarized
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P
T
PR
QRS
SA node Represented on the ECG as P wave
AV node conduction is represented on the
ECG as the PR Interval
The Bundle Branch and purkinje fibre depolarisation
constitutes ventricular depolarisation Represented
on the ECG as the QRS
Atrial repolarization occurs within the QRS &
therefore is masked
Ventricular repolarization is represented on the
ECG as a T wave
1) atrial depolarization begins
2) atrial depolarization
complete (atria contracted)
3) ventricles begin to
depolarize at apex;
atria repolarize (atria relaxed)
4) ventricular
depolarization complete
(ventricles contracted)
5) ventricles begin to repolarize at apex
6) ventricular repolarization complete (ventricles
relaxed)
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