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Knowledge of the structure and function of bones and aspects of
skeletal system generally are essential parts of training in many
therapies, such as Massage, 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 The Skeleton
generally - as opposed to the functions of particular bones.
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2.
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Types of Bones
with examples.
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3.
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The Structure of Bone
with diagram and definitions.
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1. Functions of The Skeleton
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1.
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| Support |
The skeleton is the framework
of the body, it supports the
softer tissues and provides
points of attachment for most
skeletal muscles.
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2.
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Protection
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The skeleton provides mechanical protection
for many of the body's internal organs,
reducing risk of injury to them.
For example, cranial bones protect the brain,
vertebrae protect the spinal cord, and the
ribcage protects the heart and lungs.
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3.
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| Assisting
in Movement |
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Skeletal muscles are attached to
bones, therefore when the associated
muscles contract they cause bones
to move.
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4.
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| Storage of
Minerals |
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Bone tissues store several minerals,
including calcium (Ca) and phosphorus
(P). When required, bone releases
minerals into the blood - facilitating
the balance of minerals in the body.
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5.
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| Production
of Blood Cells |
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The red bone marrow inside some larger
bones (including, for example, the
....) blood cells are produced.
(Red Blood Cells, White Blood Cells
and Platelets are described on the
page: Structure
& Functions of Blood.)
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6.
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| Storage of
Chemical Energy |
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With increasing age some bone marrow
changes from 'red bone marrow' to
'yellow bone marrow'.
Yellow bone marrow consists mainly
of adipose cells, and a few blood
cells. It is an important chemical
energy reserve.
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2. Types of Bones
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There are axial and appendicular
bones.
(The appendages are the arms
and legs, which contain approx. 30 bones each.)
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There are typically 22 bones in the head.
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There are 33 bones in the spine.
These include:
7 cervix (neck);
12 thorax;
5 lumbar;
5 sacral;
4 coccyx.
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The pelvic girdle is fused to the sacrum
at the sacro-illiac joint.
The pelvis is the part that is added onto the
spine.
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The thorax (chest) consists of 12 pairs
of ribs:
7 pairs 'true' ribs (joined directly to the sternum
("breast-bone"));
3 pairs 'false' ribs (joined to the sternum ("breast-bone")
by cartilage);
2 pairs 'floating' ribs (not connected to the
sternum ("breast-bone") at all, connected
to the diaphragm.;
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The shoulder girdle consists of the scapula
(shoulder blade) and the clavicle ("collar
bone").
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The following table summarises the five main categories
of bones, together with another category (sutural bones).
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1.
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| Long
bones: |
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"Long bones" have
greater length than width and
consist of a shaft and a variable
number of endings (extremities).
They are usually somewhat curved
for strength.
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Examples include femur, tibia,
fibula, humerus, ulna and
radius.
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2.
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Short
bones: |
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"Short bones" are roughly cube-shaped
and have approximately equal length and
width.
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Examples include ankle
and wrist bones.
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3.
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| Flat
bones: |
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"Flat bones" have a thin
shape/structure and provide considerable
mechanical protection and extensive
surfaces for muscle attachments.
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Examples include cranial
bones (protectin the brain), the
sternum and ribs (protecting the organs
in the thorax), and the scapulae (shoulder
blades).
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4.
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| Irregular
bones: |
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"Irregular bones" have
complicated shapes and so cannot be
classified into any of the above (shape-based)
categories. Their shapes are due to
the functions they fulfill within
the body e.g. providing major mechanical
support for the body yet also protecting
the spinal cord (in the case of the
vertebrae).
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Examples include the vertebrae and
some facial
bones.
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5.
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| Sesamoid
bones: |
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"Sesamoid bones" develop
in some tendons in locations where
there is considerable friction, tension,
and physical stress. They may therefore
form in the palms of the hands and
the soles of the feet, however their
presence and quantity varies considerably
from person to person.
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Examples common to everyone include
the patellae (kneecaps).
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6.
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| Sutural
bones: |
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"Sutural bones" are classified
by their location rather than by their
shape. They are very small bones located
within the sutural joints between
the cranial bones. The number of sutural
bones varies considerably from person
to person, therefore these are un-named
bones.
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3. The Structure of Bone
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Bones grow from their ends (extremities).
Under normal circumstances bones stop growing when the
owner reaches his.her late teens or early twenties.
Bone marrow (see diagram below) produces stem cells,
such as erythrocytes
(red blood cells) and leucocytes (white blood cells).
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Definitions of main types of bone tissue:
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Compact (also known
as "compact") tissue forms the outer shell
of bones. It consists of a very hard (virtually solid)
mass of bony tissue arranged in concentric layers (Haversian
systems).
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Cancellous (also
known as "spongy") tissue is located beneath
the compact bone and consists of a meshwork of bony
bars (trabeculae) with many interconnecting spaces containing
bone marrow.
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Diagram illustrating the general structure of long bones:
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The diagram above labels the basic components of a typical
long bone: articulartory (also known as 'articular') cartilage;
spongy bone; bone marrow; endosteum; compact bone; periosteum;
medullary cavity, and a blood vessel (indicating blood supply
and circulation within bones).
Articulatory (or articular) cartilage reduces friction
and absorbs shock at freely moveable joints.
Endosteum is the membrane that lines the cavity of a bones.
Periosteum is a tough fibrous membrane that surrounds
the outside of bones wherever they are not covered by articulatory
cartilage.
In adults the medullary cavity contains fatty yellow
bone marrow.
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This is the end of this page about the structure and functions
of bones.
Information about cranial
and facial bones and bones
of the feet and hands are also included on this website.
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... End of Article ...
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Revision Index.
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