2. At the end of the lesson, you should be able to
State the functions of blood:
Red blood cells – haemoglobin which aids in oxygen
transport
White blood cells – phagocytosis, antibody
formation and tissue rejection
Platelets – fibrinogen to fibrin, causing clotting
Plasma – transport of blood cells, ions, soluble food
substances, hormones, carbon dioxide, urea,
vitamins, plasma proteins
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3. What is Blood? Blood
3 types of cells present in the
human blood cell:
• red blood cells
(erythrocytes)
• white blood cells
(leukocytes) plasma, 55%
• platelets (thrombocytes)
Plasma is a liquid consisting
91% water which has
blood cells, 45%
inorganic ions, nutrients,
waste products, hormones
and soluble proteins dissolved
in it.
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4. Red Blood Cells Blood
Formed in bone marrows of long bones.
Formed from nucleated cells called erythroblasts.
Exposed to maximum surface area for the exchange of
oxygen and carbon dioxide.
95% of the protein in red blood cell is haemoglobin and
5% of the protein are enzymes that allow the cell to
survive for about 120 days.
cytoplasm
containing
haemoglobin
plasma
membrane
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5. Red Blood Cells Blood
The binding of oxygen to haemoglobin is reversible.
In the lungs, where oxygen concentration is high, oxygen
combines with haemoglobin to form oxyhaemoglobin.
When blood arrives at cells where the oxygen concentration
is low, it unloads and becomes maroon haemoglobin once
again.
high oxygen concentration
Hb + 4O2 Hb(O2)4
(haemoglobin) low oxygen concentration (oxyhaemoglobin)
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6. Red Blood Cells Blood
As red blood cells pass through tissues, they pick up carbon dioxide.
Most of the carbon dioxide combines with water to form carbonic acid.
CO2 + H2O H2CO3
carbonic
acid
The carbonic acid then ionises to form hydrogen ions and hydrogen
carbonate ions.
H2CO3 H+ + HCO¯
3
carbonic acid hydrogen hydrogen
ion carbonate ion
About 70% of the ions leave the red blood cells and remain in plasma.
When the blood reaches the lungs, carbon dioxide is released and
diffuses out of the blood to enter the alveoli.
Carbon dioxide is then breathed out.
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7. What is anaemia?
Lower red blood cell count
Caused by deficiency in
iron in diet leading to less
haemoglobin being
produced
Symptoms:
Easily tired, looks pale,
breathless
Who’s vulnerable? Pregnant
ladies, people who have lost large
amounts of blood
8. Why do people
living in high
altitudes have rosy
cheeks?
Concentration of oxygen in air is lower
Absorb insufficient oxygen for respiration
Acclimatisation Body produces more red
blood cells increase amount of haemoglobin
per unit volume of blood
Hence more oxygen can be transported to cells
9. Blood group
Red blood cells carry special protein called antigens
on their cell surfaces. Blood plasma contains
antibodies.
Blood groups are classified according to the
antibodies and antigens present in their blood.
There are four groups of blood, named A, B, AB and
O.
Each group is named after the antigen present.
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