Transport in Humans
Learning Outcomes

understand the need for and the
structure of the human circulatory
system and know that there are
two separate circulations, one to
the lungs and one to the other
organs of the body.
Why do we need a
circulatory system?
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Transport over short
distances is
achieved by
diffusion, osmosis or
active transport.
Situation in larger
organisms is different
Giant redwoods
need to transport
water to a height of
100m without the
expenditure of
energy
Why do we need a
circulatory system?
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Cell Metabolism – What do cells need?
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Amino acids, glucose, oxygen
Removal of waste products
What is important in determining
whether an organism has a transport
system?
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Size
Surface area to volume ratio
Level of activity
Double Circulation
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The heart is divided into two halves, the
left and the right. The blood on the right
side does not mix with the blood on the
left. So the circulation is in two parts.
The blood passes through the heart
twice in one circuit, this is called a
double circulation.
Blood picks up oxygen in the lungs
(oxygenated), and gives up its oxygen
to the body cells (deoxygenated).
Double Circulation
Blood
Learning Outcomes

be able to draw and label
diagrams of a white blood
cell/phagocyte and a red blood
cell and know the differences
between them; know the functions
of the four main parts of the blood:
red cells, platelets, plasma, white
cells.
The Blood
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The blood consists of four
components.
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Plasma
Red blood cells
White blood cells
Platelets
Plasma
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It has red blood cells, white blood
cells and platelets suspended in it.
Plasma transports
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Carbon dioxide from organs to lungs
Soluble products of digestion from
small intestine to other organs
Urea from liver to kidneys
platelets
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Small fragments of cells
No nucleus
Help to clot blood at site of wound
Platelets and clot formation
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When platelets in the blood are
exposed to air at a cut, proteins
(fibrinogen) in the blood plasma
form threads of fibrin.
These threads form a mesh over the
wound which traps red blood cells.
These then dry to form a scab.
White blood cells
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Have a nucleus
Two main types
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Phagocytes and lymphocytes
Help defend body against micro
organisms
Red Blood Cells
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Transport oxygen from lungs to the
organs.
Have no nucleus
Contain the pigment haemoglobin

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Oxygen + haemoglobin  oxyhaemoglobin
In the organs, oxyhaemoglobin
splits back to haemoglobin and
oxygen.
Learning Outcome

know that the heart pumps blood
around the body, is made mainly
of muscle, has its own blood supply
through the coronary vessels and
that the blood flows to the organs
through arteries and returns to the
heart through veins.
Blood Vessels
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The blood flows from the heart to organs
through arteries and returns through veins.
Arteries have thick walls containing muscle and
elastic fibres, they carry blood to the organs.
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Arteries contract and bounce back to force the
blood along,
this bouncing back can be felt as a “pulse” as the
blood flows through.
Veins have thinner walls and often have valves
to prevent the back-flow of blood.
Blood Vessels
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In the organs the blood flows
through capillaries.
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These are very narrow, thin-walled
blood vessels, they are only one cell
thick.
Substances needed by the cells in
body tissues pass out of the blood,
and substances produced by cells
pass into the blood through the walls
of the capillaries.
Structure and function of arteries, capillaries
and veins
Blood
vessel
structure
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Artery
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Vein
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Capillary
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Thick, tough wall with
muscles, elastic and
fibrous tissue
Narrow lumen
No valves
Thin wall – mainly fibrous
tissue, little muscle or
elastic tissue
Lumen large
Valve present
Wall is one cell thick, no
muscle or elastic tissue
Lumen one red blood
cell wide
Valves absent
How structure is related to function
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Carries blood at high pressure prevents bursting and maintains
pressure wave
Maintains a high blood pressure
High blood pressure stops blood flowing
backwards
Carries blood at low pressure
Reduce resistance to blood flow
Prevent back flow of blood
Allows diffusion of materials between
capillary and surrounding tissue
Blood cells pass through slowly to allow
diffusion of materials and tissue fluid
Blood pressure lower than in arteries
Learning Outcome

recognise and label on a given
diagram of the heart: the atria,
ventricles, valves, pulmonary artery,
pulmonary vein, aorta and vena
cava
The Structure of the heart
Structure of heart
pulmonary artery
vena cava
right atrium
tricuspid valve
right ventricle
aorta
pulmonary vein
left atrium
semi-lunar valve
bicuspid valve
tendon supporting
valve
left ventricle
muscle
The Heart
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The heart pumps blood through the
circulatory system all round the body.
The heart is a double pump.
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The right side collects blood from the body
and pumps it to the lungs.
The left side collects blood from the lungs
and pumps it to the rest of the body.
Heart Dissection
Heart Dissection

Cut open heart by two vertical cuts; one
through the left atrium and ventricle, the other
through the right atrium and ventricle.
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Note – the difference thickness in the walls, reason
why?
If blood vessels are still intact, try to identify which is
which.
Look for coronary arteries on the surface.
Look inside – valves between atria and ventricles;
valves at the base of the pulmonary artery and the
aorta
Learning Outcomes

be able to describe the passage of
blood through the heart including
the functions of the valves in
preventing backflow of blood.
Valves in the heart
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There are three main types of valves in
the heart. These are:
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Semi-lunar valves
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aorta and pulmonary artery
Tricuspid valves
Bicuspid valves
The valves are attached to the wall of
the heart by tendons (heart strings),
which prevent the valves being turned
inside out.
What do these valves do?
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Each valve has a particular function
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Semi-lunar valves – these prevent blood
sucking back into the ventricles when they
stop contracting.
Tricuspid valve (between the right atrium
and ventricle) and bicuspid valve (between
the left atrium and ventricle) these prevent
blood passing up into the atria when the
ventricles contract.
The Cardiac Cycle

Draw a flow chart to demonstrate
the blood flow through the heart.

Mention which muscles are
contracted
Which valves are open
Which valves are closed
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Use the diagram to help you
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The effect of exercise on
heartbeat
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A heart beat is a contraction
The heart beats about 70 times a
minute
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The lower the heart beat rate the fitter
you are
During exercise the heart rate
increases to supply the muscles
with more oxygen and glucose
Learning Outcomes

know that in the organs blood flows
through very small blood vessels
called capillaries. Substances
needed by cells pass/diffuse out of
the blood to the tissues, and
substances produced by the cells
pass/diffuse into the blood, through
the walls of the capillaries.
Capillary exchange
Capillary exchange
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The walls of capillary blood vessels are
one cell thick, allowing substances to
diffuse easily between the blood and
body cells.
The blood in capillaries supply nearby
cells with oxygen, food molecules and
other substances. It also carries carbon
dioxide and other wastes produced by
cell metabolism.
Capillary exchange
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Tissue fluid carries oxygen, food and
other substances to the cells. The fluid is
blood plasma that is forced out through
the thin capillary walls by the pressure of
the blood inside.
Red blood cells squeeze through the
smallest capillaries in single file; this
results in a drop of pressure as the blood
passes through capillaries from the
artery to the vein.