Human Growth and Development

Aging Theories ●​ Wear and Tear Theory suggests that the body, like a repeatedly played CD, gradually deteriorates over time due to constant use and stress. ●​ Cellular Accidents occur when errors happen during cell division. While most are harmless, multiple errors can lead to dysfunction . Free radicals, produced during metabolism, can damage DNA. Vitamins C and E help neutralize these harmful radicals. ●​ Error Catastrophe occurs when a body no longer has the ability to contain damaged cells that cellular accidents have caused. This aging theory usually helps explain malignant tumors . ●​ Cellular-senescence is when a cell permanently stops dividing but remains alive and inactive. While it serves as a protective mechanism, its accumulation in tissues can contribute to aging and age-related diseases. ●​ Immuno-senescence refers to the gradual decline in immune system function as people age. It contributes to the increased susceptibility of older adults to infections, autoimmune diseases, and cancer. ●​ Programmed-senescence suggests that aging is driven by a genetically programmed process, where cells and tissues age according to a biological timeline. ●​ Genetic Clock aligns with programmed senescence, suggesting that aging is regulated by genes located in the telomeres at the end of chromosomes. Conditions like Trisomy 21 (Down Syndrome) and progeria , which accelerates aging, highlight the role of genetics in aging. Leonard Hayflick's research found that cells stop dividing after a certain number of divisions, known as the Hayflick Limit, regardless of damage. Some of the visible signs of aging can be seen in the skin, hair, and body shape. Bones weaken, behavior slows, and weight loss occurs. Lifestyle factors like poor nutrition, smoking, and high blood pressure play a larger role in heart disease. Around 25% of older adults die from cancer, which often develops before symptoms appear, partly due to weakened immunity. The risk of chronic diseases increases, including arthritis, hypertension, heart disease, and stroke. Women are more likely to develop chronic conditions, while men are at higher risk for heart disease. Both genders face increased risks of heart disease and cancer, the leading causes of death. Infectious diseases also rise due to immune system decline.

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