Transcript Heart

Heart
ACCESS H.E.
HUMAN BIOLOGY.
Clare Hargreaves-Norris
Heart structure
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The heart is a hollow, cone shaped organ with cardiac muscle
forming its walls.
There are three layers which form the walls of the muscle:
endocardium, myocardium and pericardium.
The heart is approximately 10 cm long and is situated in the
thoracic cavity, behind the sternum, lying to the left side.
The heart is divided into a right and left side with the
septum separating each side.
The heart contains four chambers; two upper chambers
called the right and left atriums and two lower chambers
called the right and left ventricles.
The valves separate the atrium and ventricle chambers and
when they open and close they change the pressure within
the chambers.
Clare Hargreaves-Norris
Contraction and relaxation of the
heart
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When the cardiac muscle
contracts (at systole) it
forces the blood out of
the heart and into the
arteries which carry the
blood around the body.
When the cardiac muscle
relaxes (at diastole) the
heart fills with blood.
This mechanism of
contraction and
relaxation is known as a
heart beat.
Clare Hargreaves-Norris
The sequence the blood flows through
the heart
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Deoxygenated blood returns from the body
via the superior and inferior vena cava into
the right atrium of the heart.
The blood is squeezed through the tricuspid
valve into the right ventricle.
It is then forced out into the pulmonary
artery which transports the deoxygenated
blood to the lungs to become oxygenated.
The oxygenated blood from the lungs enters
into the left atrium of the heart via the
pulmonary veins.
The blood is squeezed through the bicuspid
valve into the left ventricle.
It is then forced into the body’s largest
artery - the aorta, which transports the
oxygenated blood to the rest of the body.
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The Heart
The Heart
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Pulmonary & Systemic Circulatory
Systems
Two distinct systems
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Pulmonary circulation
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Pulmonary circulation transports
blood from the lungs to the
heart and back.
Deoxygenated blood is taken via
the pulmonary artery from the
right ventricle of the heart to
the lungs.
The lungs enrich the blood with
oxygen.
Carbon dioxide is removed from
the blood.
Pulmonary veins carry the
oxygenated blood back to the
left atrium of the heart.
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Systemic circulation
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Systemic circulation transports
blood from the heart to the rest
of the body and back.
It carries oxygenated blood from
the left ventricle via the aorta to
the body organs and tissues.
The aorta branches off to supply
the various areas of the body.
As the blood travels around the
body, the oxygen is removed.
Carbon dioxide is picked up by the
blood.
The superior and inferior vena
cava returns the deoxygenated
blood back to the heart.
Clare Hargreaves-Norris