Transcript red blood cells

Blood
ACCESS HE
Human Biology.
Clare Hargreaves-Norris
Introduction
The circulatory system is comprised of:
 Blood, this fluid transports vital
substances to all areas of the body.
 Blood is transported in vessels known as
arteries, veins and capillaries.
 The heart acts as a pump to move the
blood around the body.
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Functions Of The Blood
The blood has three
main functions
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1. Transportation
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Red blood cells carry oxygen to the cells of the
body.
Carbon dioxide is carried back to the lungs.
Nutrients such as glucose, vitamins and minerals
are transported around the body.
Hormones are secreted into the blood and attach
to the plasma so that they can be transported
around the body to their target organs.
All waste materials such as urea are carried in the
blood to be removed and excreted.
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2. Defence
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Leucocytes (white blood cells) fight against
disease and microbe entry.
Leucocytes engulf the bacteria and destroy them
(phagocytosis).
Lymphocytes (specialised leucocytes) produce
antibodies which give the body future resistance
to re-infection.
Coagulation. Platelets start the clotting process
to prevent excessive blood loss and to stop
infection from gaining entry into the body.
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3. Regulation
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The blood regulates body heat by
absorbing it from the liver and muscles as
it passes by, and then transports it around
the body.
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Composition of blood
Blood is made from
 Plasma (55%) a strawcoloured fluid
 Erythrocytes (red
blood cells)
 Leucocytes (white
blood cells)
 Thrombocytes
(platelets)
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Structure
Plasma
90% water.
 Remaining 10%
consists of other
substances:
- blood proteins,
- mineral salts,
- nutrients,
- waste material,
- gases,
- enzymes,
- hormones,
- antibodies.
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Function
Renews the
cellular fluid.
 Maintains the
pH of the blood
at 7.4.
 Makes the
blood viscous.
 Provides
energy to the
cells.
 Produces
chemical
reactions.
 Protects
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against infection.
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Structure
Erythrocytes
(red blood
cells)
Minute biconcave discs.
 They obtain their red
colour from haemoglobin
combining with oxygen to
form oxyhaemoglobin.
 Made in the red bone
marrow.
 They take
approximately 7 days to
form.
 They then function for
approximately 4 months.
 They are then
destroyed by the liver or
spleen.
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Function
To carry
oxygen around the
body to the cells.
 To take carbon
dioxide away from
the cells.
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Leucocytes
(white blood
cells)
Structure
Function
Are colourless
cells, contain a
nucleus, and are
larger than red
blood cells.
There are fewer
leucocytes than
erythrocytes.
There is
approximately 1
leucocyte to
every 600
erythrocytes.
To fight infection.
2 main types of leucocytes:
1.
Granulocytes (75%)
Neutrophils - digest
bacteria & cell debris.
Basophils – release
histamine and heparin.
Eosinophils – combat
inflamation.
2.
Agranulocytes (25%).
Lymphocytes (23%) produce antibodies to
kill foreign proteins.
Monocytes (2%) ingest foreign proteins.
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Structure
Platelets
 Platelets are
(Thrombocytes). formed in the
red bone
marrow.
 They are tiny
fragments that
are even smaller
than red blood
cells.
Function
They produce
thrombokinase.
 Thrombokinase
starts the
‘clotting cascade’.
 Clotting cascade
is a chain of
reactions resulting
in a blood clot.
 This is an
essential part of
homeostasis to
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prevent
blood loss.
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Blood clotting
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Platelets produce a substance
called thrombokinase.
This sets off a chain of reactions
resulting in the laying of fibres.
The fibres cover the wound thus
preventing blood loss.
When the blood clots it forms a
scab.
A scab is a natural protective
seal (plaster) to the area.
This process is known as the
‘Clotting Cascade’.
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Factors affecting the blood clotting
process
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The health and efficiency of the blood
supply can be affected by:
Smoking
Alcohol
Poor nutrition intake
Anti-coagulant drugs such as warfarin and
aspirin.
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