Biomedical Engineering Reference
In-Depth Information
heart and lungs (protected by the ribcage), and spinal cord
(protected by vertebrae).
• Shape. Because of their rigid nature, bones provide a framework
around which the body is built and is kept supported. Thus,
bones are responsible for the shape and form of a human body.
• Movement. Working with skeletal muscles, tendons, ligaments,
and joints, the bones form the moving machinery of the human
body and function together to generate and transfer forces so that
individual body parts or the whole body can be manipulated in
three-dimensional space. One of the major roles of bones in move-
ment is that they act as levers, which make use of the forces gen-
erated by skeletal muscles in a beneficial way (i.e., the bones of the
upper and lower limbs pull and push, with the help of muscles).
Leg and arm movements are the most obvious examples; a less
obvious example is that ventilation of the lungs depends on
movement of the ribs by skeletal muscles. Interactions between
bones and muscles are studied in biomechanics.
• Sound transduction. Bones are important in the mechanical
aspect of hearing. In fact, our ability to hear is largely dependent
on bones. The arrangement of bones inside the ear structure is
essential for audition.
• Synthetic functions of bones
• Synthesis of blood cells. The major synthetic role of bone is in the
production of blood cells. The bones themselves are not capable
of doing this. Instead, they house the bone marrow, which con-
tains hematopoietic stem cells capable of producing blood cells.
In infants, the bone marrow of all long bones is capable of this
synthesis; as a person ages, however, the red marrow turns into
yellow fatty marrow, which is no longer capable of hematopoi-
esis. The red marrow in adults and older individuals is restricted
to the vertebrae and the heads of the tibia and femur.
• Metabolic functions of bones
• Mineral storage. Bones serve as an important storehouse of min-
erals such as calcium and phosphorus. In general, 97% of the
body's calcium is stored in bone. Here it is easily available and
turns over quickly. When required, bones release minerals into
the blood, facilitating the balance of minerals in the body.
• Fat storage. The yellow bone marrow of long bones stores fatty
acids.
• Marrow holder. This is secondary to the production of maxi-
mum strength for minimum weight: The cavities produced in
unstressed areas (like the holes in the tubes of a bicycle frame) are
used for marrow or, in some places (mastoids), just for air storage.
