Biomedical Engineering Reference
In-Depth Information
Chapter 7
Bones
The bones that form the skeleton are made of an organic matrix—collagen, and
inorganic crystals of calcium and phosphate, plus water. The bones are made to
support the body's weight as well as quite larger stresses. Collagen is responsible
for the bone's great elasticity and the inorganic crystals for their resistance to tensile
and compressive forces. The elastic properties of the bone are compared with those
of steel-reinforced concrete.
7.1 Objectives
To introduce skeleton and bones
To introduce the elastic properties of solids
To discuss the concepts of elastic moduli of solids
To discuss the elastic properties of bones
To analyze stress on intervertebral discs
To analyze the situations in which bones fracture
7.2 Skeleton and Bones
The skeleton is a mechanical structure and is composed of bones, cartilage, and
articulations. Its main functions are: body support, movement, protection of impor-
tant organs such as the brain, eyes, internal ears, heart, lungs, etc. and the storage of
chemical substances, being calcium the most important. An adult skeleton is made
up of 206 bones of different shapes and sizes, half of which belongs to hands and
feet. Due to their composition, bones are extraordinarily strong although also
extraordinarily light, mainly because of their porosity. In a standard adult the
mass of all of the bones corresponds to 14-18 % of the total body mass.
