Structure and Functions of Blood Tissue
Note: This page is part of
the section about the structure and function of different Tissue
Types, which is related to the section about
Histology and Cells (incl. structure
of animal cells, cell
division, mitosis, meiosis).
This "Tissue Types" section is included to complete description
of the knowledge of "Histology - The Cell" required
by some courses in First-Level Anatomy and Physiology. To
read
about other
tissue types see the list of on the left.
1.0 Where in the body are the blood tissues ?
The components
of blood are referred to as blood "tissue" for
the purposes of this page/section.
Blood tissues are found inside the blood vessels (arteries, arterioles, capillaries, venules and veins -
see the systemic
circulation for further details about the path
the blood follows and the names of specific blood vessels) and
also within the chambers of the heart.
Some white blood cells are also found in other types of body tissues,
for example lymphocytes are
also found in the lymphatic system.
2.0 The Structure (Physical Description) of the blood
tissues
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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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The main components of blood (i.e. types of blood cells)
are summarised in the following diagram:
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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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2.1 Physical Description of Blood
Plasma |
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Blood plasma is a pale coloured liquid that contains the
blood cells mentioned in the three sub-sections below.
It is approx. 90% water, the rest of its mass being due to dissolved substances.
These dissolved substances include food for the body's cells, waste matter
and carbon dioxide (CO2) for removal from the body, antibodies
to fight infections, and hormones and
enzyemes that control the body's processes.
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Read more about blood
plasma. |
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2.2 Physical Description of Red Blood
Cells (Erythrocytes) |
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Red blood cells (more formally called "erythrocytes")
have the physical form of disc-shaped cells that have no
nuclei when mature. They contain an iron compound called
haemoglobin which gives blood its dard red colour.
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Read more about erythrocytes.
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2.3 Physical Description of White
Blood Cells (Leucocytes) |
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White blood cells (more formally called "leucocytes")
are large opaque
blood cells - which means that they appear
to be solid rather than transparent, therefore one cannot
see
through
them. There are many different types of white blood cells,
each of which has a different physical structure and functions
within the immune system.
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Read more about leucocytes.
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2.4 Physical Description of Blood
Platelets (Thrombocytes) |
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Blood Platelets (more formally called "thrombocytes")
are very small disc-shaped bodies that do not have any nuclei.
They have an important role in blood
clotting and so they
gather at locations of injury.
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Read more about thrombocytes.
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3.0 The Functions of blood tissues
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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See also related pages about: The
Structure and Functions of Blood (similar information to
that on this page - but in more detail;
most of the information on this page is extracted from the main "The Structure and Functions of Blood" page),
the Glossary Pages about The
Components of Blood,
The
Structure and Functions of Blood Vessels (related information),
and Blood
Pressure (related information).
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