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The Human Circulatory System
and the Components of Blood
Circulatory System
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The circulatory system is also
referred to as the cardiovascular
system
Functions very closely with digestive
and respiratory systems
Basic system requires:
1. a pump (heart);
2. vessels/pathways (veins, arteries,
capillaries);
3. fluid (blood).
Circulatory System
Key Roles:
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Maintains homeostasis
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body temperature regulation
controls blood pressure
Delivers and removes substances
throughout body
Delivers
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nutrients
oxygen
messages (via hormones)
toxins
Removes
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metabolic wastes
carbon dioxide
toxins
Components of Blood
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a sample of blood can be spun in a
centrifuge
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high speed, circular motion
causes blood to separate by the weights
of its components
Components of Blood
Erythrocytes: Red Blood Cells
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Produced in bone marrow, stored in spleen
Constantly destroyed and replaced
Distinct biconcave shape
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Flattened disc that is pinched in the centre
Makes it flexible for traveling through various
blood vessels
No nucleus
No mitochondria
Contains special
hemoglobin molecule
Hemoglobin
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Complex protein made up of 4 protein
chains, each with a central iron-containing
heme group
Iron gives RBCs their distinct red colour
Iron binds with oxygen
(4 O2 molecules per
hemoglobin
molecule) – blood
becomes
oxygenated
Iron is recycled in
bone marrow
Anemia
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Medical condition when there is a less
than normal amount of hemoglobin
in the blood
Less hemoglobin, less O2 being
delivered throughout the body
Can be caused by a genetic disorder
(e.g., sickle cell anemia or
thalassemias) or by a great loss of
blood
Leucocytes: White Blood Cells
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Produced in bone marrow
Larger than red blood cells, but much
fewer in number
Amoeboid-shaped
Contain nucleus and lysosomes
Leucocytes: White Blood Cells
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Part of body’s immune response system
Detects and defends body from infection
and diseases
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Pus is formed at site of infection
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Lysosomes digest foreign bacteria
White blood cells (living & dead) + bacteria
Body’s natural “soap”
An increase in WBCs indicate the body is
fighting an infection
A problem with WBC overproduction could
mean Leukemia
Platelets
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Fragments of special cells from the
bone marrow
Important for circulatory system
repair
Form blood clots
Platelets – Blood Clotting
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Detect damaged blood vessels
Burst and release special adhesive
chemicals
Platelets stick together and form
a platelet plug
Through chemical reactions,
forms strand-like fibrin molecule
A mesh of fibrin strands forms a
blood clot
Clot protects body from losing
blood through the damaged vessel
Holds vessel wound together until it can be
reconstructed with new tissue growth
Hemophilia
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X-linked genetic disorder
Individual lacks special proteins that
are needed for creating blood clots
Can bruise easily
Can bleed excessively if cut –
sometimes bleeding to death
Shock
An actual medical condition – can be lifethreatening
 Body (or parts of body) shut down because
circulatory system cannot meet oxygen
demands of some vital organs
 Body reduces blood flow to arms and legs so it
can maximize O2 getting to the vital organs (in
body’s core)
 Can result from loss of blood, extreme fright or
emotional disturbance
First Aid:
 Put person in half upright position, keep warm
 Apply direct pressure to any areas of severe
bleeding
 Get (call for) medical help
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