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A double circulatory system
Because of this our circulatory system is in two parts.
It is in fact called a double circulatory system.
This section of the system
including the right side of
the heart, deals with the
deoxygenated blood.
Lungs
Body cells
This section of the
system including the
left side of the heart,
deals with the
oxygenated blood.
The human circulatory system
One
big
muscle
The heart is made almost entirely of muscle.
It is unlike
any other muscle in your body because it never tires.
And even though it is full of blood it still needs it own
blood supply.
Oxygenated blood is carried to the heart by the
coronary arteries.
Each side of the heart has two chambers.
1. An top chamber or atrium and
2. A bottom chamber or ventricle
Each of these chambers has its own function.
Look at the diagram on the next slide to see what that is.
Diagrammatical representation
The valves: structure and function
Besides the chambers there is also another very important part of the heart – the
valves.
These valves are found between the top and bottom chambers on both sides of the
heart.
blood
valve
These valves are rather
like doors that only open
in one direction.
Valves in action
As the atrium fills with
blood, the valves are
closed.
When the atrium contracts and
squeeze the blood, the valves
are pushed open.
These valves are connected to the side wall of the heart by tough tendons.
These tendons allow the valves to close but not invert.
Tendon holding
a
valve
valve
tendon
wall of
ventricle
These tendons can be compared to an arm holding onto the handle
of a door.
More valves
we also find valves
here
...and here!
These extra valves stop the blood from re-entering the heart when it is
pumped from the ventricles.
Lub - dub
When the blood knocks against the first heart valves, it makes a ‘lub’ like
sound.
When the blood knocks against the second set of heart valves, it
makes a ‘dub’ like sound.
The blood ‘slaps’ against the valve
and then passes along the artery.
artery
ventricle
valve
These two sounds – lub and dub – are actually what we hear as our heartbeat.
So our heartbeat is in fact the sound of the valves opening and closing.
The action in motion
Now that we can name all of the parts of the heart it is time to see how they
work to push blood around the body.
The heart pumps blood when its muscle contracts. As the muscle contracts
the chamber gets smaller and squeeze the blood out.
The two sides of the heart work together. The atria contract and relax at the
same time, as do the ventricles.
The next two slides describe what occurs inside the heart during one heart
cycle.
The actionblood
infrom
motion
blood from the
body
the lungs
1. The heart beat begins
when the heart muscles
relax and blood flows into
the atria.
2. The atria then contract and
the valves open to allow
blood into the ventricles.
The action in motion
3. The ventricles contract
forcing the blood to leave the
heart. At the same time, the
atria are relaxing and once
again filling with blood.
The staged cycle then repeats itself.
lungs
Different destinations
This journey is
far less
demanding. The
right ventricle
only has to pump
blood from the
heart to the
adjacent lungs.
This journey is
enormous.
The left
ventricle has
to pump blood
all over the
body!
body cells
Therefore, the left ventricle needs a thicker wall to generate a stronger
‘squeeze’ on the blood.
Drag the labels to the correct numbered boxes
on the diagram of the blood system.
Label the heart
Answer the questions
Multiple-choice quiz