Biomedical Engineering Reference
In-Depth Information
Patella
FIGURE 1.5
Illustration of patellar bones.
are the pisiform (smallest of the carpals) and the two small bones at
the base of the first metatarsal. Sesamoid bones are usually present
in a tendon where it passes over a joint, which serves to protect the
tendon.
Bones can also be classified based on their pattern of development and
their region. Details can be found in Appendix A.
As well, from a material standpoint, bone can be viewed as a composite
material composed of about 65% hydroxyapatite crystals and about 34 type
I collagen fibrils (by dry weight). Water in bone usually makes up 25% of
the wet weight of bone material.
1.3 Bone Functions
To allow optimal function, the arrangement of individual bones is as precise,
orderly, and purposeful as the full skeletal system itself, and their distri-
bution from top to bottom is extremely balanced. Most of the bones in our
body are structured in a symmetrical fashion. That is, many of our bones are
matched on each side of the body. This matched design allows us to balance
and stabilize ourselves in the face of various forces that act on our bodies.
With optimal arrangement, the bone forms the basic unit of the human skel-
etal system, provides the framework for bearing the weight of the body, pro-
tects the vital organs, supports mechanical movement, hosts hematopoietic
cells, and maintains iron homeostasis. These functions can be classified into
three categories:
• Mechanical functions of bones
• Protection. In numerous places inside the body, bones serve to
protect important and delicate organs, reducing risk of injury to
them. The best examples are the brain (protected by the skull),
