Transcript The Heart and Circulatory System

Circulation
The Heart and
Circulatory System
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Contents
The Heart and Circulatory System
The circulatory system
Structure of the heart
Valves in the heart
How the heart pumps blood
Summary quiz
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How do substances move around the body?
The body has its own transport
system that carries substances
around the body.
Which organs are involved in
this system?
heart
blood vessels
blood
The body’s transport system is
called the circulatory system.
Why is it given this name?
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What is carried by the circulatory system?
Which gases are transported to and from the body’s cells
by the blood flowing in the circulatory system?
carbon
dioxide
oxygen
Oxygen is the gas needed for respiration and is transported
to the body’s cells.
Carbon dioxide is the waste gas produced by respiration
that must be carried away from the body’s cells.
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Two types of blood
The circulatory system carries two types of blood:
oxygen-rich
blood
oxygen-poor
blood
 blood travelling
c
to the body cells
 blood travelling
away from the body cells
 high oxygen content
 low oxygen content
 low carbon dioxide
content
 high carbon dioxide
content
The arrangement of the circulatory system means that these
two types of blood do not mix. Why is this important?
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At the heart of the circulatory system
The heart is the organ at the centre of the circulatory system.
It pumps blood around the body.
How are the two types of blood (oxygen-rich and
oxygen-poor) kept apart inside the heart?
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Inside the heart
The inside of the heart is divided into two sections so that
the two types of blood (oxygen-rich and oxygen-poor)
are kept apart.
right side
of the heart
left side
of the heart
oxygen-poor
blood
oxygen-rich
blood
Remember that the heart is always labelled as if it is in a
body facing you, so the right side of the heart is on the
left of the diagram.
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The two sides of the heart
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How does blood circulate around the body?
Blood is pumped
around the body by
the heart.
It takes about 30
seconds for blood to
go once around the
body.
Starting with the left
side of the heart,
what route does the
blood follow to
complete one circuit
of the body?
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How does blood circulate around the body?
The left side of
the heart pumps
oxygen-rich blood
to the rest of the body.
This blood supplies
the body’s cells with
oxygen.
What gas does the
blood then pick up
from the body’s cells
and where does the
blood go next?
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body’s
cells
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How does blood circulate around the body?
Blood picks up
carbon dioxide from
the body’s cells.
This oxygen-poor
blood then travels
back to the right side
of the heart.
The oxygen-poor
blood needs to lose
the carbon dioxide and
pick up more oxygen.
How does it do this?
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body’s
cells
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How does blood circulate around the body?
Next, the right side
of the heart pumps
oxygen-poor blood
to the lungs.
lungs
In the lungs the blood
gets rid of the waste
carbon dioxide and
collects more oxygen.
Where does this
oxygen-rich blood
then travel to?
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body’s
cells
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How does blood circulate around the body?
The oxygen-rich
blood then returns
to the left side of the
heart.
lungs
This completes the
blood’s journey
around the body.
Why is the journey
of blood through the
circulatory system
called a double
circulation?
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body’s
cells
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A double circulatory system
During one complete
circuit of the body,
blood passes through
the heart twice.
lungs
The heart has two
jobs to do and so the
circulatory system
involves a double
circulation.
What are the two jobs
that the heart carries
out during this double
circulation?
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body’s
cells
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Which way does blood flow?
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Contents
The Heart and Circulatory System
The circulatory system
Structure of the heart
Valves in the heart
How the heart pumps blood
Summary quiz
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The structure of the heart – exterior
The heart pumps blood around the circulatory system.
What is the heart made of?
muscle
tissue
The heart is made of muscle and keeps pumping blood
around your body, even when you are asleep!
What do the blood vessels on the outside of the heart do?
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The heart needs blood too!
The heart is full of blood but also needs its own blood
supply so that the muscle can keep pumping.
muscle
tissue
blood vessels
supply blood
to muscle tissue
The blood vessels on the outside of the heart carry
oxygen-rich blood to the heart muscle cells.
Oxygen-poor blood is then carried away from these
cells by outer blood vessels and back into the heart.
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The structure of the heart – interior
The inside of the heart is divided into two sections to keep
oxygen-rich and oxygen-poor blood separate.
Each side of the heart is also divided into two sections.
right side
of the heart
left side
of the heart
Each section of the heart is called a chamber.
How many chambers are there?
4
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The chambers of the heart
The four chambers of the heart have special names:
An upper chamber is called an atrium (plural atria).
right
atrium
left
atrium
right
ventricle
left
ventricle
A lower chamber is called a ventricle.
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What do atria and ventricles do?
The chambers of the heart have different functions.
blood to
the lungs
blood from
the body
blood to
the body
blood from
the lungs
The atria collect blood that enters the heart.
The ventricles pump blood out of the heart.
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Inside the heart – labels
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Inside the heart – labelling activity
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Chambers of the heart – activity
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Contents
The Heart and Circulatory System
The circulatory system
Structure of the heart
Valves in the heart
How the heart pumps blood
Summary quiz
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Preventing backflow
Blood always flows in the same direction as it moves
through the heart during each circulation of the body.
Why is it important that blood does not flow backwards?
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Heart valves
The chambers of the heart are separated by valves
which prevent blood from flowing in the wrong direction.
valve leading
out of
right ventricle
valve between
right atrium and
right ventricle
valve leading
out of
left ventricle
valve between
left atrium and
left ventricle
There are valves between the atria and the ventricles…
…and there are valves leading out of the ventricles.
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Naming the heart valves
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How are valves held in place?
The valves between the atria and ventricles are connected
to the inner walls of the heart by tough tendons.
valve open
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How are valves held in place?
The tendons allow the valves to close and hold the valve
flaps in place. They prevent the valves from flipping up
and turning inside out. Why is this important?
valve open
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valve closed
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How do valves work?
A valve acts like a door that only opens in one direction.
If the door is held by someone at a fixed point, only the arm
moves as the door opens and closes.
When the door is closed the arm is fully extended, so the
door can only be opened in one direction.
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How do valves work?
A valve acts like a door that only opens in one direction.
In the heart, the tendons holding the valve are like the
arm holding the door.
One end of each tendon is fixed to the wall of the heart
and so the valve can only open in one direction.
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Contents
The Heart and Circulatory System
The circulatory system
Structure of the heart
Valves in the heart
How the heart pumps blood
Summary quiz
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How does the heart pump blood?
Imagine the force needed
to squeeze a tennis ball.
That’s how much force
the heart uses to pump
blood around the body!
How does the heart produce
enough force to keep doing
this 24 hours a day?
The heart can pump blood
because it is made of muscle.
Muscle tissue works by
contracting (squeezing)
and relaxing.
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How does the heart pump blood?
All the parts of the heart on
either side, work together
in a repeated sequence.
The two atria contract and
relax; then the two ventricles
contract and relax.
This is how blood moves
through the heart and is
pumped to the lungs and
the body.
One complete sequence of
contraction and relaxation is
called a heartbeat.
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Heartbeat animation
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Stages of a heartbeat
Stage 1:
A heartbeat begins
with the heart muscle
relaxed and valves
closed.
Blood flows into the
two atria and both
sides fill up with blood.
This blood has to be
pushed through the
valves to get into the
ventricles. How does
this happen?
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Stages of a heartbeat
Stage 2:
The atria contract and
the blood is squeezed
which causes the
valves leading to the
ventricles to open.
Blood then flows from
the atria into the
ventricles.
What happens to the
open valves when the
atria are empty?
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Stages of a heartbeat
Stage 2 (continued):
The valves between
the atria and the
ventricles close.
This prevents any
backflow.
What happens next
to the blood in the
ventricles?
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Stages of a heartbeat
Stage 3:
Almost immediately,
the ventricles contract
and the blood is
squeezed again.
The pressure of the
blood forces open the
valves leading out of
the heart.
Blood is pumped out
of the heart.
What happens to the
open valves when the
ventricles are empty?
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Stages of a heartbeat
Stage 3 (continued):
When the ventricles
are empty, the valves
leading out of the
heart close and the
heart muscle relaxes.
This completes the
sequence of
contraction and
relaxation in one
heartbeat.
What will happen
next?
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Stages of a heartbeat
Stage 1 (again):
The atria fill up with
blood as the heartbeat
sequence begins
again.
Why are the walls
of the atria thinner
than the walls of
the ventricles?
Why is the wall of the
left ventricle thicker
than the right
ventricle?
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Listening to a beating heart: lub-dub
What does a doctor hear when they listen to a patients’ heart?
lub-dub, lub-dub, lub-dub, lub-dub, lub-dub, lub-dub…
The sound of a heartbeat is the sound of the heart valves.
The “lub” is caused by
the closing of the valves
leading to the ventricles.
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The “dub” is caused by
the closing of the valves
leading out of the heart.
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Measuring a beating heart
You can measure how
fast your heart is beating
by taking your pulse.
Place the fingertips of one
hand on the opposite wrist,
where an artery passes
near the surface of the skin.
Each pulse that you feel
is due to the pressure of
blood leaving the heart as
the left ventricle contracts.
What is your heart rate,
in beats per minute,
right now?
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How many heartbeats?
If your heart beats at an average rate of 70 times
per minute, how many heartbeats are there…
…in one hour?
70 x 60 =
4, 200
…in one day?
4, 200 x 24 =
100, 800
…in one year?
100, 800 x 365 =
36, 792, 000
…in 70 years?
36, 792, 000 x 70 =
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2, 575, 440, 000
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The sequence of a heartbeat
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Journey of blood around the body
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Contents
The Heart and Circulatory System
The circulatory system
Structure of the heart
Valves in the heart
How the heart pumps blood
Summary quiz
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Multiple-choice quiz
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