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Knowledge of the structure and function of blood and other aspects
of the heart and vascular system are essential parts of training
in many therapies, such as Massage (in its many forms, "Indian
Head Massage", "Swedish Massage", "Accupressure
Massage" etc.), Aromatherapy, Acupuncture, Shiatsu, and others.
This page is intended to include the detail required for most Basic
/ First Level Courses in these therapies, and some ITEC Diplomas.
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This page is divided into the following sections:
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1.
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The Functions of
Blood
(generally - as opposed to the functions of particular components
of blood).
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2.
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The Composition
of Blood
(incl. the different types of blood cells and their properties
and functions).
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3.
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Process of Oxygenation
of Tissues due to Circulation of Blood
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4.
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Types of Leucocytes
(White Blood Cells)
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Click on the links above or scroll down this
page.
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1. Functions of Blood
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1.
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| Transports: |
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Dissolved gases (e.g. oxygen,
carbon dioxide);
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Waste products of metabolism
(e.g. water, urea);
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Hormones;
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Enzymes;
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Nutrients (such as glucose,
amino acids, micro-nutrients
(vitamins
& minerals),
fatty acids, glycerol);
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Plasma proteins (associated
with defence, such as blood-clotting
and anti-bodies);
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Blood cells (incl. white blood
cells 'leucocytes', and red
blood cells 'erythrocytes').
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2.
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Maintains
Body Temperature |
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3.
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| Controls
pH |
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The pH of blood must remain in the
range 6.8 to 7.4, otherwise it begins
to damage cells.
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4.
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| Removes toxins
from the body |
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The kidneys filter all of the blood
in the body (approx. 8 pints), 36
times every 24 hours. Toxins removed
from the blood by the kidneys leave
the body in the urine.
(Toxins also leave the body in the
form of sweat.)
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5.
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| Regulation
of Body Fluid Electrolytes |
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Excess salt is removed from the body
in urine, which may contain around
10g salt per day
(such as in the cases of people on
western diets containing more salt
than the body requires).
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2. Composition of Blood
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Blood consists of many components (constituents).
These include:
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55%
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Plasma
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45%
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Components, i.e. 'Blood Cells'.
Of these, 99% are erythrocytes (red blood cells)
and 1% are leucocytes (white blood cells) and
thrombocytes (blood platelets).
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This is summarised in the following diagram, and described
in further detail below.
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The summary chart above includes: erythrocytes (red
blood cells), thrombocytes (blood platelets) and leucocytes
(white blood cells). It also includes categories of
leucocytes: agranulocytes and granulocytes (also known
as polymorphonucleocytes), which may also be sub-divided
into lymphocytes, monocytes, basophils, neutrophils
and eosinophils.
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The following table includes further general information
about the constituents of blood.
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Structure
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Functions
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Plasma
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Normal blood plasma is 90-92 % water.
This is the straw-coloured fluid in which
the blood cells are suspended, and consists
of:
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The medium in which the blood cells
are transported around the body
(by the blood
vessels) and are able to operate
effectively.
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Helps to maintain optimum body
temperature throughout the organism.
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Helps to control the pH of the
blood and the body tissues, maintaining
this within a range at which the
cells can thrive.
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Helps to maintain an ideal balance
of electrolytes in the blood and
tissues of the body.
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Dissolved substances including electrolytes
such as sodium, chlorine, potassiun, manganese,
and calcium ions;
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Blood plasma proteins (albumin, globulin,
fibrinogen);
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Hormones.
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Erythrocytes
(Red
blood
cells)
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Immature erythrocytes have a nucleus
but mature erythrocytes have no nucleus.
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Carry oxygen (process described in more
detail - below).
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Haem
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Erythrocytes have a "prosthetic
group" (meaning "in addition
to" - in this case, in addition
to the cell). The active component
of this prosthetic group is Haem.
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Haem relies on the presence of
iron (Fe).
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Haem combines with oxygen to form
oxyhaemoglobin:
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...
continued in section below.
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Erythrocytes are eventually broken down
by the spleen into the blood pigments
bilinubin and bilviridin, and iron. These
components are then transported by the
blood to the liver where the iron is re-cycled
for use by new erythrocytes, and the blood
pigments form bile salts. (Bile breaks
down fats.)
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Have a longevity of approx. 120 days.
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There are approx. 4.5 - 5.8 million erythrocytes
per micro-litre of healthy blood (though
there are variations between racial groups
and men/women).
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Leucocytes
(White
blood
cells)
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There are different types of leucocytes
(described in more detail - below),
classified as:
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Granular: e.g. Neutrophils,
Eosinophils, Basophils.
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Agranular (do not contain
granules): e.g. Monocytes, Lymphocytes.
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Major part of the immune system.
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Have a longevity of a few hours to a
few days (but some can remain for many
years).
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There are approx. 5,000 - 10,000 leucocytes
per micro-litre of blood.
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Trombocytes
(Platelets)
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Blood platelets are cell fragments;
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To facilitate blood clotting - the purpose
of which is to prevent loss of body fluids.
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Disk-shaped;
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Diameter 2-4 um
(1 micro-metre = 1 um = 0.000001m);
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Have many granules but no nucleus;
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Have a longevity of approx. 5-9 days.
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There are approx. 150,000 - 400,000 platelets
per micro-litre of blood.
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3. The Oxygenation of Blood
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The oxygenation of blood is the function of the erythrocytes
(red blood cells) and takes place in the lungs.
The sequence of events of the blood becoming oxygenated (in
the lungs) then oxygenating the tissues (in the body) is as
follows:
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The Right Ventricle (of the heart) sends de-oxygenated
blood to the lungs.
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While in the lungs:
1. Carbon Dioxide diffuses out of the blood into the
lungs, and
2. Oxygen (breathed into the lungs) combines with haemoglobin
in the blood as it passes through the lung capillaries.
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Oxyhaemoglobin returns to the heart via the pulmonary
vein and then enters the systemic circulation via the
aorta.
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There is a low concentration of oxygen in the body
tissues. They also contain waste products of the metabolism
(such as carbon dioxide).
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Due to the high concentration of oxygen in the blood
and the low concentration of oxygen in the tissues,
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... the high concentration of carbon dioxide in the
tissues diffuses into the blood. (95% of this carbon
dioxide dissolves in the blood plasma.)
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Blood returns from the tissues back to the heart via
the superior vena cava (from the upper-body) and the
inferior vena cava (from the lower-body)
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4. Types of Leucocytes (White Blood
Cells)
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Lymphocytes:
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Monocytes:
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*Basophils:
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*Neutrophils:
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*Eosinophils:
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Approx. 24% of leucocytes are lymphocytes.
These produce anti-bodies and include:
*T-Cells
*B-Cells
*Natural
Killer Cells
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Approx. 4% of leucocytes
are monoocytes. These are also known as phagocytes.
They combat microbes by the process of phagocytosis.
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60-70%
of leucocytes are basophils.
Diameter 10-12 micro-metres.
Phagocytosis. Destruction of bacteria with lysozyme
and strong oxidants.
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2-4% of
leucocytes are neutrophils.
Diameter 10-12 micro-metres.
Combat the effects of histamine in allergic reactions;
Phagocytize antigen-antibody complexes;
Destroy some parasitic worms.
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0.5-1%
of leucocytes are eosinophils.
Diameter 8-10 micro-metres.
Liberate heparin, histamine, and seratonin in allergic
reactions, intensifying inflammatory response.
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* It is only possible to observe the
differences between these by staining them.
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Further notes about the types of leucocytes identified
above:
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| Lymphocytes: |
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The term "antigen" refers to something
that is not naturally present and 'should not
be in the body'.
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T Cells (lymphocytes) are activated by the thymus
gland.
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B Cells (lymphocytes) are activated by other
lymphoid tissue. The 'B' indicates 'bone marrow'
cells.
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Both T-cells and B-cells:
(1) destroy antigens, and
(2) produce 'memory cells' and anti-bodies.
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| Basophils: |
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An increased (higher than usual) percentage of
basophils in the blood may indicate an inflammatory
condition somewhere in the body.
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| Neutrophils &
Monocytes: |
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Neutrophils are the first leucocytes to
respond to bacterial invasion of the body. They
act by carrying out the process of phagocytosis
(see opposite), and also be releasing enzymes
- such as lysozyme, that destroy certain bacteria.
Monocytes take longer to reach the site
of infection than neutrophils - but they eventually
arrive in much larger numbers.Monocytes that migrate
into infected tissues develop into cells called
wandering macrophages that can phagocytize
many more microbes than neutrophils are able to.
Monocytes also clear up cellular debris after
an infection.
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| Eosinophils: |
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An increased (higher than usual) percentage of
eosinophils in the blood may indicate parasitic
infection somewhere in the body.
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Phagocytosis:
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A phagocyte is a cell able to engulf and
digest bacteria, protozoa, cells, cell debris,
and other small particles. Phagocytes include
many leucocytes (white blood cells) and macrophages
- which play a major role in the body's defence
system.
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Phagocytosis is the engulfment and digestion
of bacteria and other anigens by phagocytes.
This is illustrated below.
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This is the end of this article but further information about
blood vessels, the structure
and functions of the heart,
systemic circulation, and the vascular system generally
are included on other pages of this website. (These are presented
separately to minimise the download-times of image-intensive
pages.)
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More revision pages are added to this website approximately
weekly.
... End of Article ...
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