American Academy of Health and Fitness
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Integumentary (Skin) System
Skeletal System
Muscular System
Nervous System
Endocrine System
Cardiovascular System
Lymphatic (Immune) System
Respiratory System
Digestive System
Urinary System
Reproductive System

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Skeletal System

The major functions of this system are in structural support, protection of soft tissues, mineral storage, and blood production.

The 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.


Fun fact:

The 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.

Once the 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.

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Contact Information:

American Academy of Health and Fitness
Phone 800-95-SRFIT (800-957-7348)
Fax (703) 451-4952

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