Download Chapter 5: Blood and Circulation

MAKING SENSE OF
THE BLOOD
IGCSE Biology
2.3 Blood and Circulation
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MrExham.com
Image © Depositphotos.com/[julos #4371007]
3cm
2cm
1cm
• Its all to do with surface area to volume ratio.
• Small organisms have a larger surface area to
volume ratio then larger organisms.
1cm
3cm
2cm
Width of cube
(cm)
Surface area
(cm2)
Volume
(cm3)
Surface area: volume
1
6
1
6
2
24
8
3
3
54
27
2
• Single celled organisms = large surface area to
volume ratio
• They can rely on diffusion to get what they
need and remove wastes.
Single celled organisms viewed down a microscope
• Larger multicellular organisms = small surface
are to volume ratio
• therefore need a circulatory system to supply
all the cells with what they need.
– Provide oxygen
– Remove carbon dioxide
– Provide nutrients
– Remove urea
– Provide hormones
– Provide antibodies
• Can you recall the composition of blood?
• What is the role of plasma in the transport of carbon
dioxide, digested food, urea, hormones and heat
energy?
• How are red blood cells adapted for transporting
oxygen?
• How does the immune system respond to disease
(pathogens) using phagocytes and lymphocytes?
• Can you explain how vaccinations work?
• How are platelets involved in blood clotting?
• If you take a sample of blood and spin it in a
centrifuge very quickly it will separate into two
layers.
• The blood cells will go to the bottom and a light
straw coloured liquid called plasma comes to the
top.
• If you take a sample of blood and spin it in a
centrifuge very quickly it will separate into two
layers.
• The blood cells will go to the bottom and a light
straw coloured liquid called plasma comes to the
top.
55% plasma
Centrifuge
45% blood cells
• Also known as
.
• They are made in the bone marrow.
• Their function is to carry oxygen around the
body.
• These are the most numerous of all the blood
cells, in every cubic millimetre of blood there
are 5,000,000 cells.
disc shape.
• large surface area to volume ratio,
– lots of oxygen can get to the centre of each cell by
diffusion.
• don’t have a nucleus.
– carry more
.
• Haemoglobin is a carrier protein which picks
up oxygen and forms
.
Oxygen + Haemoglobin  oxyhaemoglobin
• The oxygen is delivered to the respiring cells.
Biconcave shape = increase SA for diffusion
No nucleus = more space for haemoglobin
• To protect our body against the invasion of
disease causing organisms (pathogens).
• This is done in two ways:
– Phagocytosis (by phagocytes)
– Antibody production (by lymphocytes)
• 70% of our white blood cells are phagocytes.
• These can engulf bacteria by the process of
phagocytosis.
Watch this video
of phagocytosis.
• 70% of our white blood cells are phagocytes.
• These can engulf bacteria by the process of
phagocytosis.
Bacteria (Pathogen)
Phagocyte
• 70% of our white blood cells are phagocytes.
• These can engulf bacteria by the process of
phagocytosis.
• 70% of our white blood cells are phagocytes.
• These can engulf bacteria by the process of
phagocytosis.
• 70% of our white blood cells are phagocytes.
• These can engulf bacteria by the process of
phagocytosis.
Digestive enzymes
released by the cell to
breakdown and destroy
pathogen.
• Approximately 25% of our white blood cells
are lymphocytes.
• Their function is to produce
.
• Pathogens have markers on their surface
membranes called
.
• Antibodies stick to these and destroy the
pathogen.
Antibodies
Pathogen
Antigen
• Antibodies stop pathogens in a number of
ways:
– Cause bacteria to burst.
– Cause the bacteria to stick together making it
easier for phagocytes to ingest them.
– Neutralising toxins produced by the pathogens.
• Some lymphocytes develop into memory cells.
• Remain in blood for many years and provide
immunity to that specific pathogen.
• If it enters the blood again we will recognise it
faster and mass produce the antibodies
quicker.
• This is called the
.
• Sometimes we can trick the body into thinking
it’s been infected.
• This will give us the immunological memory so
that if we really get infected, the secondary
immune response will occur.
• The vaccination can be one of these things:
– A dead pathogen
– A weakened strain of the actual pathogen
– Modified toxins of the bacteria
– The antigens removed from a pathogen
• Platelets are small fragments of cells that help
your blood to clot when you cut yourself.
• This stops bleeding and prevents infection of
the wound.
• They produce a chemical which causes a
plasma protein called
to change
into
.
• Fibrin forms the clot.
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
• Over 90% of plasma is water.
• The plasma transports the following things:
.