Transcript What is Blood?

KS4 Biology
What is Blood?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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Blood and the circulatory system
The circulatory system is
made up of the heart, blood
and blood vessels.
What exactly is blood and
what does it do?
Blood is the fluid that flows
in the circulatory system
and carries substances
around the body.
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How much blood?
How many litres of blood are
there in the circulatory system
of an average adult?
5.5 litres
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What is blood made of?
Blood is made up of a liquid
called plasma and blood cells
that float in this plasma.
If a test tube of blood is left
to stand for a while what
happens to it?
The blood cells sink to the
bottom of the test tube and
separate from the plasma
which is a clear yellow liquid.
The liquid in blood is yellow!
So why does blood look red?
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plasma
(55% of
volume)
blood cells
(45% of
volume)
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Different types of blood cells
Blood plasma carries three types of blood cells.
They have different shapes and carry out different functions.
red
blood cell
white
blood cell
platelet
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What’s in a drop of blood?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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What does plasma do?
Blood flows around the body
transporting substances from
one place to another.
Plasma is the blood fluid that
surrounds blood cells and
carries them along as it flows
through the blood vessels.
Plasma is mostly water and
contains other substances that
are dissolved in it.
What useful and waste
substances are dissolved in
and transported by plasma?
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What is dissolved in plasma?
Plasma is mostly water with other
substances dissolved in it.
 Useful substances dissolved
in plasma are digested food.
This must be transported to
where it is needed in the body.
 Waste substances dissolved
in plasma are carbon dioxide
and urea.
These must be transported to
where they can be removed
from the body.
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Plasma: transporting digested food
The digestive system breaks long insoluble molecules of
food into small soluble molecules that the body can use.
Where does soluble digested food enter the blood?
digested food
in blood plasma
Soluble digested food diffuses from the small intestine
into the bloodstream and dissolves in the plasma.
The digested food is then carried to the body’s cells
and used in various chemical reactions.
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Plasma: transporting carbon dioxide
Carbon dioxide is produced by respiration in the body’s cells.
This waste product is poisonous to the body and so must
be removed as quickly as possible. How does this happen?
carbon dioxide
in blood plasma
Carbon dioxide diffuses from body cells into the blood
where it dissolves in plasma.
Carbon dioxide then carried from the cells to the lungs.
How is this waste product finally removed from the body?
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Plasma: transporting urea
Urea is another waste substance that is transported by the
blood. It is made in the liver.
Urea is toxic to the body and must be removed as quickly
as possible.
urea
in blood plasma
Urea enters the blood in the liver and dissolves in plasma.
It is then carried from the liver to the kidneys.
The kidneys filter blood and remove urea from plasma.
This waste product is then removed from the body in urine.
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Dissolved substances in plasma
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What does plasma do?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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What do red blood cells do?
Red blood cells are the most
common type of blood cell.
The job of red blood cells is to transport oxygen from the
lungs to the body’s cells, where is used in respiration.
oxygen
The body contains millions and millions of red blood cells.
Why does it need so many?
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Features of a red blood cell
A red blood cell has several features that help it do its job:
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It contains
haemoglobin,
a special pigment
that combines
with oxygen.
Disc-shaped, with
a dent on each
side, creates a
large surface area
for gas exchange.
It has no nucleus,
so there is more
space for
haemoglobin and
so more oxygen.
A large surface
area compared to
volume, so oxygen
is always close to
the surface.
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Another feature of red blood cell
Another important feature of a red blood cell is its size.
The diameter of a red blood cell is slightly bigger
than the average diameter of a capillary.
How does this help the release of oxygen?
The size of a red blood cell forces it to slow down as it
passes through a capillary. The surface of the red blood
cell is exposed to the surface of the capillary and so gas
exchange will definitely happen.
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Features of a red blood cell – activity
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Red blood cells and haemoglobin
Haemoglobin is the special pigment in red blood cells.
At the lungs, oxygen diffuses into red blood cells and
combines with haemoglobin to form oxyhaemoglobin.
oxygen
+
oxyhaemoglobin
haemoglobin
This is how red blood cells are able to bind to oxygen and
carry it in the blood.
Oxyhaemoglobin makes red blood cells appear bright red.
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Red blood cells and haemoglobin
Red blood cells loaded with oxyhaemoglobin carry oxygen
from the lungs to the body’s cells.
Here, oxyhaemoglobin changes back to haemoglobin and
oxygen is released.
oxyhaemoglobin
haemoglobin
+
oxygen
Oxygen is then able to diffuse into the body’s cells.
Why do red blood cells appear a dull red colour when
oxygen is released?
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Journey of a red blood cell
Oxygen enters the body
when air is inhaled into
the lungs.
oxygen +
haemoglobin
How does this oxygen
enter the blood?
Oxygen diffuses from
the alveoli on the
surface of the lungs
into the bloodstream.
The oxygen then
diffuses into the red
blood cells where it
meets haemoglobin.
(not to scale)
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Journey of a red blood cell
In the red blood cells
at the lungs, oxygen
combines with
haemoglobin to form
oxyhaemoglobin.
This oxygen-rich
blood travels from
the lungs, through the
circulatory system,
to body cells.
How does oxygen get
from red blood cells
into the body’s cells?
oxygen +
haemoglobin
oxyhaemoglobin
oxyhaemoglobin
oxyhaemoglobin
oxyhaemoglobin
(not to scale)
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Journey of a red blood cell
When red blood cells
reach the body’s cells,
oxyhaemoglobin
changes back to
haemoglobin and
oxygen is released.
Oxygen then diffuses
from the red blood cells
across the lining of the
capillary and into the
body’s cells.
What happens next to
the red blood cells?
oxygen +
haemoglobin
oxyhaemoglobin
oxyhaemoglobin
oxyhaemoglobin
oxyhaemoglobin
haemoglobin
+ oxygen
(not to scale)
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Journey of a red blood cell
Red blood cells that
have released oxygen
to the body’s cells have
to get back to the lungs.
oxygen +
haemoglobin
oxyhaemoglobin
oxyhaemoglobin
So this oxygen-poor
blood travels from the
body’s cells through the
circulatory system.
At the lungs, the red
blood cells can pick up
more oxygen and start
another journey around
the body.
oxyhaemoglobin
oxyhaemoglobin
haemoglobin
+ oxygen
(not to scale)
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Red blood cells in an alvelous
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Red blood cells in a capillary bed
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How do red blood cells carry oxygen?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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What do white blood cells do?
White blood cells are the largest type of blood cell.
They have a large nucleus and can change their shape.
White blood cells protect the body from disease by
fighting invading microbes that can cause infection.
White blood cells can squeeze through the walls of
capillaries. How does this help them fight against
microbes?
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Different types of white blood cells
Different types of white blood cells protect the body
in different ways:
Some white blood cells fight against infection by
surrounding invading microbes and then digesting them!
Other white blood cells produce antibodies or antitoxins
to fight against infection.
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White blood cell count
Doctors can check the number of white blood
cells in a person’s blood to find out if they are
healthy or fighting off an infection.
healthy
white blood cell
count is low
unwell
white blood cell
number is high
Why is the white blood cell count higher when a person
is fighting off an infection?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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What do platelets do?
Platelets are the third type of blood cell.
platelet
They are important for blood clotting.
Platelets are cell fragments that have broken off from
other larger cells.
They are much smaller than red and white blood cells
and do not have a nucleus.
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Platelets and blood clotting
1 Platelets help to
make tiny fibres
that form a net at
the site of a cut.
2 Red blood cells
are trapped in
this net forming
a blood clot.
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3 The clot dries and
forms a scab which
protects the cut
while new skin grows.
Why is it important
not to pick a scab?
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Contents
What is Blood?
What is blood made of?
Plasma
Red blood cells
White blood cells
Platelets
Summary activities
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What do blood cells do?
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Which type of blood cell?
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Multiple-choice quiz
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