Aging notes

Aging Notes

  • Aging is a normal physiological process
    • Vital organs begin to lose some function during adulthood. Most people do not notice this loss immediately, because organs are rarely used to their fullest ability
    • Mainly associated with cellular changes produced by genetic and environmental/lifestyle factors
  • Each person ages differently (not predictable)
    • Although some changes always occur with aging, they occur at different rates and to different extents
  • Distinction between aging and disease is unclear
  • Maximal life span of humans: 80-100 years; average life span has improved in Western countries

THEORIES OF CELL AGING

  • How or why people age is poorly understood
  • There are several theories:
  • Wear and tear theory: Chemical insults and free radicals have cumulative effects on cellular function. Exposure to harmful environmental factors can affect the rate at which we age.
  • Immune system disorders: Autoimmune responses and progressive weakening of the immune response compromise health
  • Genetic theory: Cessation of mitosis and cell aging are programmed into genes; cells cannot divide forever. Telomere shortening occurs each cell division and once too short division stops.

Cellular Changes

  • Cells vary in how they change with age
    • Atrophy; some cells shrink causing a decrease in the size of a tissue or organ; common in skeletal muscle, the heart, the brain, and the sex organs
    • Hypertrophy; many cells become larger and less able to divide; there is an increase in cellular inclusions (not ICF)
    • Plasma membranes changes result in decreased transport into and out of the cell
  • Many cells lose their ability to function, or function abnormally
    • Dysplasia: The size, shape, or organization of mature cells becomes abnormal
    • Metaplasia: abnormal change in the nature of a tissue
  • The reproduction rate of some cells increases
    • They may or may not have unusual shapes and abnormal function
    • Hyperplasia: The enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells
    • Neoplasia: The formation of tumours, either cancerous (malignant) or non-cancerous (benign)
  • As aging continues, waste products build up in tissue
    • eg lipofuscin (an age-relate pigment) and fat collects
    • Many tissues become more stiff and rigid🡪 increased resistance to blood flow 🡪 poor tissue perfusion 🡪 cells do not receive adequate blood supply 🡪 homeostatic imbalance
  • Homeostatic imbalances = poor health

Aging and the Integumentary System

  • Shortening and decrease in the number of capillary loops; blood vessels of the dermis become more fragile. Epidermal replacement slows, skin becomes thin = Increased bruising, senile purpura, cherry angiomas etc
  • Skin strength and elasticity, and subcutaneous fat decrease = Wrinkles, elastosis and cold intolerance
  • A decrease in the numbers of functional melanocytes and Langerhans’ cells; melanocytes increase in size = pale skin, gray hair and atypical pigmentation eg age spots, decreased sun protection
  • Atrophy of the sebaceous glands; produce less oil/sebum = Skin becomes dry (dehydrated) and itchy; cracking occurs; Nails may also become more brittle
  • Atrophy of the sweat glands = decreased ability to thermoregulate
  • May be less able to sense touch, pressure, vibration, heat, and cold
  • Older people at increased risk of:
  • Injury to the skin, slowed wound healing, pressure ulcers, increased risk of infection and decreased ability to thermoregulate
  • Skin tags, warts, and rough patches (keratoses)
  • Increased risk of skin cancer

Aging and the Skeletal System

  • Bones lose mass/density
  • Bone remodelling time is lengthened and bone resorption predominates
  • Faster in women after menopause (oestrogen aids in normal density of a female skeleton)
  • Bones to become stiff and brittle with decreased strength; may break more easily
  • Osteoporosis (aka osteopenia): bone thinning disease
    • 50% of women over age 65; 20% of men over age 70
    • Bones become fragile and can easily fracture
    • Vertebral collapse results in kyphosis
  • Cartilage becomes more rigid, fragile, stiff; ligaments and tendons shorten and weaken; synovial fluid may decrease = Decreased range of motion (ROM)
  • Joint problems ranging from mild stiffness to osteoarthritis are very common in older people. Full ROM exercises key to postponing joint problems
  • Costal cartilages ossify, causing the thorax to become rigid impacting on breathing
  • Intervertebral discs degenerate: become thin, less hydrated, and less elastic = Risk of disc herniation increases; loss of stature by age 55; posture may become more stooped (bent).

Aging and the Muscular System

  • Muscle tissue is lost. Muscle fibres decrease (atrophy); replacement slows = Decrease in muscle strength and bulk/mass (sarcopenia)
  • By age 30, loss of muscle mass (sarcopenia) begins
      • Muscle strength at 85 is about half that at age 25
      • Regular exercise reverses sarcopenia
  • Lost muscle tissue may be replaced with a connective tissue
    • Lipofuscin and fat are deposited in muscle tissue = reduced functionality
    • Connective tissue increases 🡪 reduced lean muscle mass 🡪 decreased per cent of total body water 🡪 higher risk for developing dehydration
  • Muscle weakness contributes to fatigue, reduced activity tolerance, gait changes, and instability = Increased risk of falls
  • Changes in the muscles and tendons cause reduced reflexes
  • Involuntary movements (muscle tremors and fasciculations) are more common in the older people
  • Older people who are not active may have weakness or abnormal sensations (paresthesias)

Aging and the Cardiovascular System - Heart

  • Sclerosis and thickening of heart valves. May lead to a heart murmur and heart valve diseases
  • Fibrosis of cardiac muscle; deposits of lipofuscin = Reduced functionality if the myocardium
  • Decreased cardiac output; decline in cardiac reserve; slower heart recovery rate
  • Abnormal rhythms (arrhythmias), such as atrial fibrillation, are more common in older people
  • The baroreceptors become less sensitive with aging. May contribute to orthostatic hypotension which is common in older people

Aging and the Cardiovascular System - Blood Vessels

  • Progressive arteriosclerosis (thickening, hardening and stiffening of artery walls) and atherosclerosis (a specific type of arteriosclerosis due to plaque formation; plaques = buildup of fats, cholesterol and other substances)
  • May result in coronary artery disease 🡪 angina and heart attack
  • May block distal arteries leading to intermittent claudication 🡪 severe pain in leg muscles
  • Transient ischemic attacks (TIA) or strokes can occur if blood flow to the brain is disrupted
  • Loss of elasticity of vessels leads to hypertension
  • Venous valves weaken; varicose veins
  • The capillary walls thicken slightly = slower rate of exchange of nutrients and wastes

Aging and the Cardiovascular System - Blood

  • Only changes slightly with age
  • Decrease in blood volume. Aging cause a reduction in total body water
  • Erythrocyte plasma membranes become fragile
  • Reduced red blood cell production in response to stress and illness = a slower response to blood loss and increased risk of anaemia
  • Neutrophils decrease in number and function = Increased risk of infection

Aging and the Respiratory System

  • Stiffening of the chest wall; diaphragm weakens; elasticity of lungs decreases; increases in flow resistance (airways close easily); increased alveoli size; thickened capillaries
  • Decreased chest wall compliance and vital capacity 🡪 Shortness of breath and decreased exercise tolerance
  • Alterations in gas exchange 🡪 blood oxygen levels decrease; stimulating effects of carbon dioxide decrease
  • Elderly are often hypoxic and exhibit sleep apnea
  • Nerves in the airways that trigger coughing become less sensitive; reduced numbers of cilia
    • Decreased effectiveness of cough and mucus clearance
    • More risks of infection eg pneumonia and bronchitis

Aging and the Nervous System - CNS & PNS

  • Brain and spinal cord lose neurons and weight (atrophy); fewer dendritic processes; less myelin
    • Slowing of neurological responses; cognitive decline
    • Deterioration of sensory function
  • Increased permeability of the blood–brain barrier; reduced cerebral circulation
    • plaques and tangles may form due to waste product accumulation 🡪 May lead to Alzheimer’s and dementia
  • Less myelin, nerve impulse conduction slows; lipofuscin can build up in nerve tissue
    • Nerve degeneration 🡪 reduced or loss of neuromuscular control, reflexes or sensations 🡪 problems with movement and safety
  • Diminished thirst perception 🡪 lower water intake 🡪 higher risk for developing dehydration

Aging and the Nervous System - Special Senses

  • Vision. The lens loses clarity, dilator muscles are less efficient 🡪 Presbyopia —“old vision”, visual acuity is drastically decreased by age 70. Problems of aging also include: glaucoma, cataracts, and arteriosclerosis of the eye’s blood vessels
  • Hearing and equilibrium. Changes in the ear structure result in reduced hearing and equilibrium. eg Otosclerosis (fusing of ear ossicles) 🡪 Presbycusis
  • Taste and smell. Decrease in sensitivity after age 40 as the number of olfactory and gustatory receptors decreases

Aging and the Lymphatic and Immune System

  • Lymphatic vessels degenerate; increased vessel permeability
  • compromised lymph flow and tissue fluid homeostasis
  • decreased lymph transport to the lymph nodes oedema; decreased pathogen transport
  • pathogen escape from lymphatic tissues into surrounding tissues
  • Decreased T and B cell activity – the immune system begins to wane, and incidence of cancer increases
  • Impaired inflammation due to chronic illness eg diabetes, cardiovascular disease, etc.
  • Healing response is diminished because of skin’s loss of regenerative ability
  • Infections are more common in older adults

Aging and the Endocrine System

  • Most endocrine organs operate smoothly until very old age
  • Atrophy of some endocrine organs including the pituitary gland (master gland)
  • Decreased production and clearance of some hormones
  • eg Decline in growth hormone production 🡪 muscle atrophy, bone loss
  • Fibrosis and inflammation of thyroid gland
  • Reduced thyroid hormone production 🡪 contributes to lower basal metabolic rates
  • Reduced calcitonin production
  • Decreasing function of female ovaries at menopause leads problems associated with reduced oestrogen levels
  • Breasts lose fat, tissue, and mammary glands
  • Decreased bone density, thinning of skin
  • Increased total blood cholesterol levels and falling HDL
  • Increased risk of osteoporosis, cardiovascular disease, hypertension, myocardial infarction, changes to brain function (irritability and depression in some)
  • Testosterone also diminishes with age, effect is not usually seen until very old age eg increased body fat and reduced muscle bulk
  • Parathyroid hormone levels rise with age 🡪 may contribute to osteoporosis
  • Insulin production doesn’t change but cells become more insulin resistant with age
  • Altered output of endocrine glands leads to a generalized increase in incidence of: Tissue loss, Diabetes mellitus, Decreased metabolic rate, Immune system depression, Cancer rates in some areas

Aging and the Digestive System

  • Tooth enamel and dentin wear down; gum recession; bone loss from jaw. Teeth are lost; increased risk of periodontal disease
  • Decreased saliva production; increased difficulty swallowing (dysphagia)
  • GI tract and pancreas atrophy 🡪 digestive enzyme activity declines, delayed gastric emptying; absorption is less efficient, and peristalsis (GI tract motility) is slowed
  • Impaired absorption of vitamin B12, calcium, iron, folate
  • Age-related problems include: Diverticulosis, faecal incontinence, and cancer of the GI tract

Aging and the Urinary System

  • Renal decline
  • Blood vessels harden 🡪 decreased renal blood flow and GFR
  • Amount of kidney tissue and nephrons decreases
  • Increased risk for drug toxicity
  • Bladder changes: becomes less stretchy causing a decrease in capacity and detrusor weakens; sphincters weaken
  • The urethra can become blocked
  • ♀ due to bladder, uterus or vagina prolapse caused by weakened muscles
  • ♂ due to enlarged prostate gland (hyperplasia)
  • Increased risk of urinary incontinence or retention

Aging and the Reproductive System - Female

  • Perimenopause – transition from a regular menstrual cycle to menopause
  • Menopause - a whole year has passed without menstruation
  • Ovaries stop functioning as endocrine organs (stop making oestrogens and progesterone)
  • Childbearing ability ends
  • Vaginal walls become thinner, dryer, and less elastic; external genital tissue decreases and thins
  • The usual age range is 45 to 55
  • Increase risk of yeast infections (thrush)
  • Decreasing sex hormone results in lower sex drive (libido) and sexual response

Aging and the Reproductive System - Male

  • Testosterone levels decline after 20 years
  • Male climacteric (less well defined than in females)
  • Decreased erectile and ejaculatory function, and libido

Aging: Summary Body System Changes

  • Integumentary: skin thins - decreased protection against trauma, sun protection and temperature changes; diminished secretion of oil and sweat
  • Musculoskeletal: Loss of bone and muscle; degeneration of joints; reduced reflexes; changes in gait, instability
  • Cardiovascular: Decreased cardiac output and reserve; slower heart recovery rate; hypertension; orthostatic hypotension
  • Respiratory: Decreased chest wall compliance and vital capacity; Decreased gas exchange; Decreased effectiveness of cough and mucus clearance
  • Nervous: Brain, spinal cord and nerve tissue; Reduced speed of nerve conduction; Slowing of neurological responses and cognitive decline; Deterioration of sensory function
  • Lymphatic and Immune: Compromised lymph flow and tissue fluid homeostasis; decreased pathogen transport and increased; impaired inflammation; decreased T and B cell activity; slow healing
  • Endocrine: Atrophy or fibrosis of some glands reduces hormone production leading various homeostatic imbalances
  • Digestive: Teeth loss; dysphagia; reduced digestive activity, nutrient absorption and peristalsis
  • Aging: Summary Body System Changes
  • Urinary: atrophy of kidneys and renal decline; decreased bladder capacity; increased risk of urinary incontinence or retention
  • Reproductive: ♀ Menopause - Ovaries stop functioning and hormone production ceases; childbearing ability ends; ♂ Testosterone decline; decreasing sex hormone results in lower libido and sexual response