Transcript KS4 What is Blood

Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
Plasma and cells in suspension
If blood is separated it no longer looks like the red liquid
that we recognise.
centrifuge
55%
45%
The blood sample separates into two parts.
The top half is a straw coloured liquid called plasma.
The bottom half is a dark collection of blood cells.
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How a suspension works
As blood is 55% plasma and only 45% cells, the cells are
actually suspended within the plasma, a little like people
would be suspended within a swimming pool.
Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
First function of plasma
The plasma actually surrounds the cells and carries them
along as it flows through the blood vessels.
This is the first function of plasma.
Blood flows around the body, transporting substances
from one place to another.
Transport role
it usually picks up a substance
from an exchange site
takes it to a place where it is used
a reaction occurs
reaction
a useful product and a waste
product is made
Shifting the product
The blood then transports one or both of these
substances to another place in the body.
cell
blood vessel
useful/waste product
The cycle then starts again.
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Products dissolved in plasma
Blood has to rely on its plasma to transport some of these
useful or waste products.
For example, plasma carries CO2 from the cells to the lungs.
blood flowing along a
capillary
plasma
CO2
CO2
CO2
blood cell
CO2
CO2
blood cell
Dissolved digestive products
The third and fourth roles are also centred around the
moving of a substance from one place to another.
Plasma is responsible for carrying dissolved food.
Remember!
Our digestive system breaks down the food we eat to
release the useful nutrients.
Summary of absorption
Mouth
food is eaten
Sugars
Useful products of
digestion are absorbed
from the digestive system
and enter the blood.
Amino acids
Glycerol
Fatty acids
Anus
waste is excreted
Leaving the plasma
The soluble food dissolves into the plasma and is carried
from the small intestine to the cells of the body.
Here they diffuse into the cells and are used in various
chemical reactions.
glycerol
sugars
amino acids
plasma
body cell
fatty acids
Removing urea
The final role of the plasma is to carry a particular waste
product from the liver to the kidneys.
The waste product is called urea.
Urea is made in the liver by the breakdown of
amino acids.
As urea is toxic, it must be removed from the body as
quickly as possible!
The blood now has to help the body do this.
Filtration and expulsion of urea
Plasma carries the urea from the liver to the kidneys
that filter the blood. Urea is removed from the plasma
of the blood and passes down a tube to the bladder.
kidney
blood
urea
This urea in the bladder is stored before it is excreted. The
urea will leave the body within the liquid urine.
Reviewing the role of plasma
Plasma – role summary
In summary, plasma has a principle role in transporting
substances around the body.
substance
moving from
going to
CO2
cells
lungs
Cells
all over
the body
Dissolved
food
small
intestine
Urea
liver
cells
kidney
The full load
All this is being carried in just the plasma!
white
blood cell
platelets
sugar
fatty
acids
red blood
cell
amino
acids
urea
carbon dioxide
Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
Blood cells
There are 3 types of blood cell within human blood.
They have different shapes and carry out different functions.
Platelets
Red Blood
Cells
White Blood
Cells
(These are actually
fragments of cells so we
can’t really call them cells)
Image of the 3 constituents
red blood
cells
white blood
cells
platelets
Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
Red blood cells: erythrocytes
Of all the cells these are the most numerous.
In fact, every cubic centimetre of blood contains…
1 cm
1 cm
1 cm
5 000,000,000 cells
Basic diagram of a red blood cell
Therefore, it is not hard to realise that each red
blood cell is extremely small.
In fact, each one is only on average 7 micrometers in
diameter (one micrometer is a millionth of a metre).
This is a basic diagram
of a red blood cell.
Inside the red blood cells
Actually, although the red blood cell is a “cell”,
it does not contain one of the 3 parts of a
“normal” cell.
Red blood cells have no nucleus.
This may seem odd but, there is a reason for it.
Red blood cells also contain a unique substance
called haemoglobin.
This is a special iron based pigment whose
presence is essential if the red blood cell is to
perform its job.
Fe2+
Oxygen for carbon dioxide
Red blood cells carry OXYGEN (O2).
The story begins in the lungs because this is where the
oxygen gas enters the bloodstream.
Remember, during the process of breathing, oxygen gas
enters the body and is exchanged for carbon dioxide gas.
The oxygen gas will be needed for the process of respiration.
O2 diffusion
O2
oxygen is inhaled
O2
O2
It passes through the
breathing system and
reaches an alveolus.
O2
O2 O2
O2
The oxygen gas diffuses
across the lining of the
alveolus and the capillary.
alveolus
Inside the alveoli
Here is a close up showing the diffusion of oxygen gas.
As the oxygen gas diffuses across the lining of the
alveolus, it dissolves in the moist layer.
This speeds up the diffusion process.
O2
moist layer
lining of alveolus
lining of capillary
red blood cell
O2
Oxyhaemoglobin
If we now concentrate on one red blood cell, we can
see how important the haemoglobin molecule is to the
process of transporting oxygen.
The oxygen molecule
diffuses into the red
blood cell.
each red blood cell
contains the pigment...
Haemoglobin + O2
Oxyhaemoglobin
These two molecules bind together to
produce this new substance.
Oxygen binding at the alveolus
It is important to remember that this reaction is
happening in red blood cells at the alveolus.
This is how the red blood cells are able to bind hold of
the oxygen and carry it within the blood.
Oxyhaemoglobin
Oxyhaemoglobin
Oxyhaemoglobin
Each red blood cell is now Oxyhaemoglobin
loaded with oxygen molecules.
Oxyhaemoglobin
Oxyhaemoglobin
Order the following events
Offloading the oxygen to body cells
Once these red blood cells reach the cells of the
body, they are travelling through tiny capillaries
similar to those found in the alveolus.
capillary
cells
It is here that they offload their oxygen.
In order for this to happen, the oxyhaemoglobin
molecule must be broken down.
Oxygen diffusion at the capillary bed
Oxygen use in the body
ENERGY
In the cell, the oxygen is used in the
process of respiration which produces….
It diffuses across the cell
membrane and the lining of
the capillary and into the cell.
The oxyhaemoglobin breaks down to
release the oxygen molecule.
Features of red blood cells
1 There are vast numbers of them.
The more cells there are, the more O2 can be carried
and delivered to the cells.
Features of red blood cells
2 They have no nucleus.
This means they have more room for haemoglobin
molecules and therefore each red blood cell can carry
more oxygen gas.
Features of red blood cells
They have a large surface area compared to their
3
volume.
large surface area
small volume
Through having a small volume compared to its
surface area, the red blood cell is able to keep the
oxygen close to its surface.
Features of red blood cells
This means it can quickly release its oxygen by reducing
the time it takes for the gas to diffuse out of the cell.
The distance for the gas to move
is much smaller in a cell shaped
like this.
alternative
cell design
O2
O2
The overall effect of this means that the blood can
cope with the oxygen demands of the body.
Features of red blood cells
4 The diameter of red blood cells is slightly larger
than the average diameter of a capillary.
capillary
red blood cell
This means that the red blood cell is forced to slow down as it
passes through the capillary.
This means the exchange of the gas will definitely happen.
It also means the surface of the red blood cell will be
exposed to the surface of the capillary.
Red blood cell features
Useful or useless?
Diffusion at the capillary bed level
Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
White blood cell
Let’s now consider the white blood cell.
The white blood cell is bigger than the red blood cell.
It has a much more varied shape and there are
different types of white blood cell within the blood.
Role in defence
White blood cells play a part in the defence system
of the body.
There are far fewer white blood cells within the blood
compared with red blood cells.
They are designed to fight microbes such as bacteria
and viruses.
White blood cell count
When the body fights disease, more white blood cells
are produced. With some diseases, doctors can
establish how healthy someone is by testing their blood
to see how many white blood cells they have.
Disease
test
white blood cell
number is low
test
white blood cell
number is higher
Match the cells to the correct functions
Blood cell differences
Our final blood part is the platelet
As we mentioned, the platelet is actually a fragment
of a cell.
Therefore it does not have a nucleus.
They are also much smaller than both the white and
red blood cells.
Their role is to help to clot the blood when the
body has a wound.
cut
skin
Contents
What is Blood?
Plasma and cells in suspension
Plasma functions
Blood cells
Red blood cells
White blood cells
Summary quiz
Multiple-choice quiz