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In-Depth Information
as system of articulated levers through a series of joints. In this structure there
is a degree of compromise between strength and flexibility. The rigidity of
the structure allows for greater strength, stability, and protection, whereas
the structure's articulation allows for more flexibility and a greater range of
movement. The cost of achieving flexibility is that joints do not have the same
degree of strength as the rest of the bones.
The number of bones in the adult human skeleton is 206 (which may vary
slightly from individual to individual), but at birth a newborn baby has
approximately 300 bones. The difference between the two numbers is a
result of the fusing together of a number of the smaller bones during growth.
In a healthy adult, the skeleton accounts for around 14% of the total body
weight.
The skeleton is complex structure of a wide variety of bones, which can be
classified into four major groups:
•
Long bones
•
Short bones
•
Flat bones
•
Irregular bones
Long Bones
Long bones are generally cylindrical in shape and broaden out to become
knobbier at each end. Bones in this category are found in the arms (humerus,
ulna, and radius) and the legs (femur, tibia, and fibula). They are also to be
found in the hand (metacarpals and phalanges) and the feet (metatarsals and
phalanges).
Short Bones
Short bones are generally solid and thickset and are typified by bones in the
wrist (carpals) and in the ankle (tarsals).
Flat Bones
The pelvic bones, sternum, and scapula fall into the category of flat bones.
Irregular Bones
The 24 vertebrae that make up the spinal column fall into the category of
irregular bones, as do the sacrum and the coccyx.
The necessary articulation in the skeleton is achieved through a series of
joints that interconnect the separate bones. These joints allow the bones
to be moved in relation to each other by the transmission of force through
the connected muscle. All joints are not the same, and they vary in both
their stability and flexibility. A joint's stability relates to its resistance to
displacement and has a direct impact on the amount of flexibility it provides;
