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The Effects of Aging On The Body: The Effects of Aging on Cells: 1) 2) 3) 4) 5) 6) 7) 8) Finite number of divisions (Hayflick limit) Molecular damage by free radicals Molecular (protein) damage by glucose Accumulation of sugars, fats, proteins, RNA Decline in DNA Mitochondria accumulate damage Hydrolysis by rampant lysosomal enzymes Decline in cell number (30% by age 75) The Effects of Aging on Skin: 1) 2) 3) 4) Collagen cross linkage Age lines increase Photoaging Chronological aging The Effects of Aging on the Nervous System: 1) Thousands of neurons lost per day after age 30 2) 7% loss in brain mass by age 80 3) Cerebral cortex loses 45% of cells by age 80 4) Neurotransmitter production declines 5) Fewer cells + less transmitter = slower 6) Peripheral nervous functional loss results in decrease sensitivity to pain, loss of smell, taste, hearing balance The Effects of Aging on the Cardiovascular System: 1) Heart enlarges 2) Myocardium replaced by fat, collagen 3) Loss of reserve capacity at 1% per year after age 30 4) Loss of elasticity of vessels results in hypertension, inefficient control of local flow The Effects of Aging on the Respiratory System: 1) Lungs lose elasticity 2) Respiratory membrane thickens 3) Breathing is more labored The Effects of Aging on the Musculoskeletal System: 1) 2) 3) 4) Osteocyte activity continues Loss of bone mass in BOTH sexes Osteoporosis common in women Muscle mass declines The Effects of Aging on the Digestive System: 1) 2) 3) 4) 5) Loss of tone, slower peristalsis Ca, B-12, Zn less well absorbed Enzymes – OK Gall bladder slows, stones develop Liver metabolizes alcohol, drugs more slowly The Effects of Aging on the Immune System: 1) 2) 3) 4) Thymus gland involutes T-cell number and function decline B-cells identify antigen less efficiently Increased incidence of autoimmunity The Effects of Aging on the Reproductive System: 1) Increased risk of certain fetal genetic defects 2) Female - menopause 3) Male - significant decline in testosterone and sperm after 65 4) Male benign prostatitis 5) Increased risk some cancers The Effects of Aging on the Excretory System: 1) Decreased renal blood flow reduces kidney function 2) Nephron number decreases 3) Less ability to concentrate urine 4) Bladder capacity declines The Effects of Aging on the Endocrine System: 1) most glands continue to function normally. Hayflick Limit: 1961 - Leonard Hayflick and Paul Moorhead discovered that human cells derived from embryonic tissues could only divide a finite number of times in culture. The Hayflick limit is the maximal number of cell division that a cell can achieve in vitro. When cells reach this limit they undergo morphological and biochemical changes that eventually lead to arrest of cell proliferation a processes called cell senescence Cell senescence is the phenomenon by which normal diploid cells stop diving.