Strong enough to protect our vital organs, intricately
structured to keep the body upright and flexible enough to allow great freedom
of movement - the human skeleton is a marvel of mechanical and architectural
Human bone is light enough for our muscles to move it easily but as strong
and tough as concrete. It can support great weights without bending, breaking or
Linked by joints and moved by muscles attached at either end, our bones
provide both protective cages for our soft and delicate organs and a flexible
scaffolding that supports our body.
Each of the different parts of the skeleton is designed to do a particular job.
The skull or cranium protects the brain and also the eyes and ears. The lower
jaw and teeth are attached to it, enabling us to chew our food. There are holes
for the eyes, ears, nose and mouth and also one in the base of the skull where
it joins the spinal column. The spinal cord passes through this, connecting the
brain to every other part of the body.
STRONG AND FLEXIBLE
The spine forms the central axis of the skeleton and is made up of a chain of
small bones, rather like cotton reels, called vertebrae. It is very strong but,
because it is made up of several small sections instead
of one solid piece of bone, it is also very flexible. This allows us a full
range of movement from touching our toes to standing upright. We can also twist
from side to side.
The vertebrae also protect the spinal cord which passes through the middle of
them. Between each of the vertebrae are discs of cartilage which cushion the
vertebrae and protect them from rubbing as we move. The bottom end of the spinal
column is called the coccyx - the remains of what was once a tail.
The rib cage is made up of the ribs, the costal cartilages, the breastbone,
or sternum, in the front and the spinal column at the back. It encloses the
heart and lungs and protects them from injury.
The arms articulate with the shoulder joints which are made up of the scapula
(shoulderblade) and the clavicle (collarbone). The large bone of the upper arm
is called the humerus and is joined at the elbow to the two bones of the
forearm, the radius and ulna.
The hand and wrist are made up of a large number of small bones. This makes
it possible for us to grip things and to carry out precise and complicated
movements using all the bones in co-ordination.
The legs are attached to the spine by the pelvic girdle, which shields the
reproductive organs and the bladder. In women, it partially protects a
developing baby which lies in this part of its mother's body.
The femur - the thick bone of the thigh - is the longest bone in the body.
Its round head fits into the socket in the pelvis to form the ball-and-socket
hip joint. This is designed to give the leg maximum freedom of movement.
There are two bones in the lower leg: the shin bone, or tibia, and the much
thinner fibula. Like the hand, the foot is made up of a complex arrangement of
small bones. This gives us the strength to stand firmly
and the flexibility to walk and run without falling over.
At birth, we have more bones than we do as adults, This is because, as we
grow, many of these bones fuse together into larger units. A baby's skull is a
good example of this. During birth, it is squeezed through a narrow canal and,
were it inflexible, the baby wouldn't be able to pass through the mother's
The fontanelles, or small gapsbetween the various sections of a baby's skull,
allow it to be moulded to the birth canal. These fontanelles slowly close up
during the next 18 months of life.
The skeleton of a child is made not only of bone, but also of flexible
cartilage. As the child grows, the cartilage gradually hardens and becomes bone
- a process known as ossification. It is not until the age of about 20 that the
bones finally 'set'.
The proportions of the human skeleton change quite dramatically as we mature.
The head of a six-week-old embryo is as long as its body. At birth, the midpoint
of a baby's skeleton has moved from its chin to its navel and by adulthood, when
the bones reach their full growth, it is just above the genitals.
Each individual has his own 'timetable' for skeletal growth, but it can be
affected by environmental factors such as diet and disease. For instance, there
are certain glandular disorders which can cause too much or too little growth: a
lack of vitamin D can lead to rickets and occasionally people are born with
extra bones, such as an extra pair of ribs or a sixth finger.
In general, a woman's frame is lighter and smaller than a man's. Her pelvis
is proportionately wider and it allows room for the growing foetus during
pregnancy. The male shoulders are broader and the rib-cage longer but, contrary
to the popular myth, men and women do have the same number of ribs.