Download the heart - Doktorscience

The Heart:
Muscular organ located between
lungs
32 000 000 beats per year!
structure
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Composed of myocardium (cardiac muscle
tissue)
Inside the heart is lined with endocardium
(squamous epithelial)
Outside of heart is lined with pericardium
which forms pericardial sac (for heart
lubrication)
The heart is divided into two halves by the
septum
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Two halves of the heart are divided into 4
chambers
Blood flow through the heart is controlled
by valves
The atrio-ventricular valves are held in
place by chordae tendinae
The semi lunar valves direct flow out of the
heart (resemble a half moon)
Function
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The heart acts as a double pump
The right side of the heart pumps blood to
the lungs (called the pulmonary circuit)
The left side pumps blood to the rest of the
body (called systemic circuit)
This is why the left side of the heart is
larger (has to pump blood farther)
Pathway of blood
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Venae cavae (inferior and superior) to the
right atrium
Right atrium to right ventricle
Right ventricle to pulmonary artery (to
lungs/pulmonary veins and back to heart)
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Left atrium to left ventricle
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Left ventricle to aorta to the body
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Systole – contraction: first atria contract,
then ventricles
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Diastole – relaxation
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Sound: lub-dupp
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Lub: atrioventricular valves close
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Dupp: closing of semi-lunar valves
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Heart murmur often due to ineffective
valves (hear a “slush” sound instead of
“lub”) this can cause back-flow in the heart
Blood pressure
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Average = 120/80 mm Hg
systole of left ventricle
diastole of left ventricle
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The ratio of the contraction and relaxations
Heart beat control
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The heart beat is intrinsic, meaning it can
beat independently of the central nervous
system
The heart has its own pacemaker: the
sino-atrial node
This is located in the upper dorsal wall of
the right atrium
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The SA node initiates the heart beat by
causing the atria to contract
The electrical impulse then reaches the
atrio-ventricular node located at the base
of the right atrium
The signal is then transmitted through the
ventricles by purkinje fibres
This then causes the ventricles to contract
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The heart is controlled by the nervous
system at the medulla oblongota (brain
stem)
Heart beat is sped up or slowed down
depending on what your body requires
Electrocardiogram (ECG) shows voltage
changes across the heart during
contraction