major functions of this system are in structural support, protection of
soft tissues, mineral storage, and blood production.
bones of the skeletal system become thinner and relatively weaker as a
normal part of the aging process. Everyone begins to lose bone mass
between the ages of 30 and 40. Over this period of time, the number of
osteoblasts (bone building cells) begins to decline, while the number
of osteoclasts (cells that break down bone) remains the same. The
balance between the activities of osteoblasts and osteoclasts is very
important when it comes to the maintenance of bone health and strength;
when osteoclasts remove calcium faster than osteoblasts can deposit it,
bones become weaker.
skeleton undergoes continual remodeling which is defined as the
replacement of old bone with new bone.
As a matter of fact, bone is completely regenerated
every 10 years.
number of osteoblasts declines, women lose roughly 8% of their skeletal
mass each decade, while men lose about 3% each decade. All parts of the
skeleton are not equally affected. The ends of long bones (like the
humerus), vertebrae, and the jaws lose more than their fair share which
results in fragile limbs, a reduction in height, and the loss of teeth.
Thus, a significant percentage of women and a smaller proportion of men
suffer from osteoporosis, a condition characterized by reduced bone
mass sufficient enough to compromise normal functioning.
A decline in
sex hormones, as well as aging itself, both contribute to the loss of
bone density. In men, testosterone production declines gradually, so
bone loss is linear and slow. In women, a rapid phase of bone loss
occurs during the first 5 to 10 years after menopause due to the
immediate and dramatic decrease in estrogen. In addition to this rapid
bone loss during early menopause, women accumulate less skeletal mass
than men during their growing years -- particularly during puberty.
This results in smaller, narrower, more fragile bones with thinner
cortices. In old age, therefore, the consequences of bone loss are
greater among women than among men, and the incidence of bone fractures
is two-to-threefold higher.