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The Heart
The Heart
• Muscular pump, about the size of a clenched
fist
Approximately 12cm long
9cm wide
6cm thick
Weighs approx 11 ounces
The average adult heart beats –
• 72 times a minute;
• 100,000 times a day;
• 3,600,000 times a year;
• 2.5 billion times during a lifetime.
 Because the heart has its own electrical impulse, it can
continue to beat even when separated from the body, as long
as it has an adequate supply of oxygen
 When the body is at rest,
it takes only 6 seconds for the blood to go from the heart to the
lungs and back,
only 8 seconds for it to go the brain and back,
and only 16 seconds for it to reach the toes and travel all the
way back to the heart
 5% of blood supplies the heart,
15-20% goes to the brain and central nervous system,
and 22% goes to the kidneys.
The Heart continued
Made up of a special muscle
called Myocardium
This can contract continuously
without getting tired
Main purpose is to drive blood
through the arteries
This delivers blood to the working
muscles and other tissues.
The heart is located in the chest
cavity - posterior to the
breastbone, between the lungs
and superior to the diaphragm
• The Heart sits in a twin layered sac known
as the Pericardium
– Filled with pericardial fluid
• Prevents friction as your heart beats.
The heart is split into 4 sectionsRight & Left side – separated by the septum
Upper & Lower chambers – the atria & ventricles
Atria
 Latin for “entrance hall,”
The upper chambers of the heart
They receive blood.
 Right Atrium – receives deoxygenated blood from the body
(Via the Vena Cava)
 Left Atrium – receives oxygenated blood from the lungs
(Via the pulmonary Vein)
Ventricles
Latin for “little belly.”
The lower chambers of the heart
They have thicker walls and are stronger
Job is to pump the blood
– Right Ventricle pumps blood to the lungs (pulmonary
circulation)
– Left ventricle pumps blood to the body (systemic
circulation)
Valves
The “thump-thump” of a heartbeat is the sound made by the four valves of the
heart closing
All valves make sure that the blood flows in one direction, and there is no back
flow
• Pulmonary Valve
• Aortic Valve
• Bicuspid Valve
(mitral valve)
• Tricuspid Valve
•Chordae Tendineae
Cord like tendons that
connect to the
tricuspid and bicuspid
valves
Ensure the valves
stay the right way
round and keep the
blood flowing in the
same direction.
Aorta and Vena Cava
The largest vein is the
Vena Cava
Carries blood directly
into the right atrium
from the body
- Superior vena cava
– brings blood
from the upper
body
– Inferior Vena Cava
– Brings blood
from the lower
body.
The largest Artery is
the Aorta
– Carries
oxygenated
blood directly
out of the left
ventricle to the
body tissues
Pulmonary Circulation
• Pulmonary Vein
• Pulmonary
Artery
Carries oxygenated
blood from the
lungs to the left
atrium
It is the only vein
that carries
oxygenated
blood.
Carries
deoxygenated
blood from the
right ventricle to
the lungs.
It is the only artery
that carries
deoxygenated
blood
The Heart = Double pump
• To describe the flow of blood
around the heart and the body,
you will need to mention that
the heart is made up of two
pumps
– Pulmonary circulation
• Pumps blood to and from
the lungs
– Systemic circulation
• Pumps blood around the
body
The
side of the heart
• Blood enters the heart from the body via the vena cavae,
• It goes into the right atrium
• The right atrium contracts and the blood goes through the
•
•
•
•
tricuspid valve and into the right ventricle
The right ventricle contracts and the blood is pushed out of
the heart through the semi lunar or pulmonary valve and into
the pulmonary artery
The pulmonary artery carries the blood to the lungs
The heart relaxes and the valves close to stop back flow of the
blood
In the lungs, the blood becomes oxygenated, and begins it’s
journey back to the heart through the pulmonary vein
The
side of the heart
• The heart is relaxed, and this allows blood to enter the left atrium from the
pulmonary vein
• The left atrium contracts and pushes blood through the bicuspid valve and
into the left ventricle
• The left ventricle has a very strong muscular wall and contracts very
strongly.
• This closes the bicuspid valve to prevent backflow, and pushes the blood
through the aortic valve and into the aorta. This is the largest artery and
splits taking the blood to different areas of the body
• The heart contracts and the aortic valve closes, preventing back flow of the
blood.
Cardiac Conduction
 Cardiac conduction is the rate at which the heart conducts
electrical impulses.
 Cardiac muscle cells contract spontaneously and are
coordinated by the sinoatrial node (the pacemaker) located in
the right atrium
 Other factors that influence heart rate include endocrine
hormones, body temperature and exercise.
Cardiac Cycle
 The cardiac cycle is the sequence of events that occur when
the heart beats.
 There are two phases of this cycle which are the diastole and
systole phases.
 During the diastole phase, the atria and ventricles are relaxed
and blood flows into the atria and ventricles.
 In the systole phase, the ventricles contract sending blood to
the rest of the body.
Terminology
• Heart rate (H.R.)
– The amount of times the heart beats in a
minute.
• Usually measured in beats per minute
(b.p.m.)
• Stroke Volume (S.V.)
– The amount of blood leaving the left
ventricle in one beat.
• Normally measure in mililitres
• Cardiac Output
– The amount of blood leaving the heart in
one minute
• Normally measured in litres/minute
• Cardiac Output = Stroke Volume x Heart
Rate
Superior
Vena cava
Aorta
Pulmonary
Artery
Pulmonary Valve
Pulmonary
Vein
Right Atrium
Left Atrium
Tricuspid
Valve
Right
Ventricle
Inferior
Vena cava
Left
Ventricle
Bicuspid
Valve
Septum