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The structure of the Heart.
The Heart is two separate pumps
side by side. The left pump deals
with oxygenated blood from the
lungs, the right with
deoxygenated blood from the
body. The reason there are two
pumps is because blood has to
pass through tiny capillaries in
the lungs in order to present a
large surface area for gases. This
drops blood pressure, so
mammals have a system where
the oxygenated blood returns
back to the heart in order to
increase pressure and pass it to
the rest of the body. This is
called a double circulatory…read more

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Structure of the heart
On each side you have:
Atrium ­ upper part of heart.
Thin-walled, elastic, stretches
as it collects blood. Only has to
pump blood short distance to
Ventricle ­ lower part of heart.
Thick muscular wall as it has to
pump long distance either to
lungs or rest of body.
Valves ­ to prevent backflow of
blood into atria when
ventricles contract.
Blood vessels ­ these carry blood
towards or away from the
heart. Ventricles pump blood
away from heart and into
arteries and atria receive blood…read more

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Component Left side of Heart Right side of Heart
Atrium Relatively the same Relatively the same
Ventricle Thicker muscular wall, enabling it Thinner muscular wall, only
to create enough pressure to pump needs to pump blood short
blood to extremities of body. distance to the lungs.
Valves Left atrioventricular (bicuspid) Right atrioventricular( tricuspid)
valves ­ two cup-shaped flaps valves ­ three cup-shaped flaps.
Arteries Aorta ­ connected to left ventricle, Pulmonary artery- connected to
carries oxygenated blood to all right ventricle, carries
part of body, (not lungs). deoxygenated blood to lungs.
(usually arteries carry oxygenated
Veins Pulmonary Vein ­ connected to Vena Cava ­ connected to right
left atrium and brings oxygenated atrium, brings deoxygenated
blood back from lungs. (usually blood back from tissues of body.
veins carry deoxygenated blood)…read more

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Structure of Heart
The heart muscles is supplied by its own blood
vessels called the coronary arteries, which
branch off the aorta shortly after it leave the
heart.…read more

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Cardiac Cycle
There are two main phases:
Diastole ­ relaxing of the heart.
Systole ­ contracting of the heart.
Blood is always moving from a region of higher pressure to a region of
lower pressure. However there are situations within the circulatory
system when pressure differences would result in blood flowing in
the wrong direction. There are why valves are used to prevent back
Atrioventricular valves ­ these are between the atrium and ventricles
on both sides. They are open when atria are contracting and blood is
flowing from atria to ventricles. They are closed when ventricles
contract and pressure is high in ventricles and low in atria. The
valves then shut preventing blood flow back into the atria and
ensuring that blood flows into aorta and pulmonary artery.
Semi-lunar valves ­ these are in the aorta and pulmonary artery. They
are open when ventricles contract and force blood up into the aorta
and pulmonary artery. They are closed to prevent blood running
back into the ventricles when the recoil action of elastic walls in
vessels causes a higher pressure in vessels than in ventricle.…read more

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