AGING
Introduction
Aging is a natural process, yet worldwide we are in
search of anti-aging
solutions. With the advances of technology and antiaging
research we are fortunate to have the choice of
many anti-aging products
and treatments.
Some make you look and feel younger, whilst others concentrate
on slowing the aging process. To best understand how
these products and treatments work, and what impact
we can expect on the body, its helpful to understand
exactly what aging is, and how the body ages.
What Is Aging?
Aging is the predictable maturing of living organisms,
although the rate of aging varies greatly among individuals.
There are two distinct types of aging:
- Intrinsic - caused by the genes
we inherit. Regarded as the natural aging that commences
at age 20
- Extrinsic - caused by environmental
factors, such as exposure to the sun’s rays.
The physical manifestations
of aging, our appearance, results largely from our
“invisible aging” at cell level. The nucleus
of every cell has 23 pairs of chromosomes. And they
contain DNA or the genetic material of the cell. A prime
cause of aging is every cell’s chromosomes are
capped with a protein button called a telomere.
As individuals age, these telomeres wear out and fray,
slowing and halting the ability of the cells chromosomes
to divide and make new cells. Normally, cells divide
75 times over a lifetime and afterwards the cell dies.
How Long Can We Realistically Expect to Live?
The maximum natural or biological life span is theoretically
defined as the average number of years of life that
is expected for a member of a population. Like most
species, humans almost always die of disease or accident
before they reach their biologic limit.
Different cultures experience different expected life
spans. This difference is generally based upon genetics,
diet,
stress factors
and environmental
hazards. In the United States, the life span, which
is estimated at 85 to 100 years, has remained about
the same over the past 50 years. Life expectancy, however,
is reduced by about 20 years due to the top ten causes
of death.
Aging of Cells
Studies into the aging of the human body are still
regarded as work in progress; however, a few clearly
defined theories are widely supported in the medical
research field.
The cells of the human body have significantly different
life spans. Since aging at the cellular level is the
greatest contributor to how old we look on the outside,
it is worth understanding the physiology in a little
more detail.
The red and white blood cells only survive a few weeks
to months. Red blood cells survival averages about four
months, after which they trigger a mechanism for their
removal from the blood.
Cells with long life spans [years to decades] include
nerves, muscles, heart cells, and reproductive cells.
It is difficult to determine what changes are due to
age and what changes are due to disease or environmental
influences. As you will recall from Biology classes,
cells renew themselves by dividing.
The aging of cells can be classified according to
their rate of replication:
- Cells that are continuously dividing - cells in
the bone marrow that produce red and white blood cells
and the cells that line the gastrointestinal tract.
- Cells that are resting but can be stimulated to
divide - cells that function to respond to tissue
injury, found in the liver, parts of the kidney, and
the cells lining blood vessels
- Cells that are past the replicating phase altogether.
This suggests the body has a mechanism for identifying
and eliminating older body cells. Little is known about
aging and cell death in long-lived cells. Nerves, which
have been extensively studied in humans, are lost at
different rates in different parts of the brain.
A cell's ability to reproduce typically declines with
normal cellular aging, yet many age-related health problems
involve increases in proliferation. For example, the
prostate gland tends to increase its cells with age.
One hypothesis is that aging may cause inappropriate
cellular responses to signals to proliferate and to
signals that tell cells to stop proliferating.
Normal Aging and Disease
Aging is not the accumulation of disease, although
aging and disease are related in subtle and complex
ways. Several conditions once thought to be part of
normal human aging have been shown to be due to disease.
For example, heart
and blood vessel diseases are less common in populations
that eat no meat and little fat, and cataract formation
in the eye is largely dependent on the degree of exposure
to ultraviolet
radiation in sunlight.
The range of individual response to aging deserves
emphasis. Biologic and chronologic age are not the same,
and body systems do not age at the same rate within
any individual. You might have marked arthritis
or severe loss of vision while enjoying excellent heart
or kidney function. Even those aging changes that are
considered usual or normal do not necessarily represent
the optimum outcome for an aging individual or society.
NEXT: Causes Of
Aging
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