Page 76 - Textbook of Pathology, 6th Edition

60 2. Genetic control in invertebrates. Clock (clk) genes mechanism appears to be oxidative damage to mitochondria.
responsible for controlling the rate and time of aging have The role of antioxidant in retarding the oxidant damage has
been identified in lower invertebrates e.g. clk-1 gene mutation been reported in some studies.
in the metazoa, Caenorhabditis elegans, results in prolonging
the lifespan of the worm and slowing of some metabolic ORGAN CHANGES IN AGING
functions.
Although all organs start showing deterioration with aging,
3. Diseases of accelerated aging. Aging under genetic following organs show evident morphologic and functional
control in human beings is supported by the observation of changes:
high concordance in lifespan of identical twins. A heritable 1. Cardiovascular system: Atherosclerosis, arteriosclerosis with
SECTION I
condition associated with signs of accelerated aging process calcification, Mönckeberg’s medial calcification, brown
is termed progeria and is characterised by baldness, cataracts, atrophy of heart, loss of elastic tissue from aorta and major
and coronary artery disease. Another example is Werner’s arterial trunks causing their dilatation.
syndrome, a rare autosomal recessive disease, characterised 2. Nervous system: Atrophy of gyri and sulci, Alzheimer’s
by similar features of premature aging, atherosclerosis and disease, Parkinson’s disease.
risk for development of various cancers. 3. Musculoskeletal system: Degenerative bone diseases,
4. Oxidative stress hypothesis (free radical-mediated frequent fractures due to loss of bone density, age related
injury).Currently, it is believed that aging is partly caused muscular degeneration.
by progressive and reversible molecular oxidative damage 4. Eyes: Deterioration of vision due to cataract and vascular
due to persistent oxidative stress on the human cells. In changes in retina.
normal cells, very small amount (3%) of total oxygen 5. Hearing: Disability in hearing due to senility is related to
consumption by the cell is converted into reactive oxygen otosclerosis.
species. The rate of generation of reactive oxygen species is 6. Immune system: Reduced IgG response to antigens, frequent
directly correlated with metabolic rate of the organisms. With and severe infections.
aging, there is low metabolic rate with generation of toxic 7. Skin: Laxity of skin due to loss of elastic tissue.
oxygen radicals, which fail to get eliminated causing their 8. Cancers: As discussed later in Chapter 8, 80% of cancers
accumulation and hence cell damage. The underlying occur in the age range of 50 and 80 years.

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General Pathology and Basic Techniques