Changes in Ageing
Growth Repair Ageing & Death of Class 12
Individuals age at different rates. Even within same person the organs show different rates of decline. Some generalization are made though do not apply to all persons. Changes at 70 years age are :
Heart : Increases in size pumping efficacy decreases upto 65%, and hence blood supply to some vital organs also decreases. Heart rate increases.
Lungs : Vital capacity (normal 3000-4600 ml) decline by 44%.
Kidney : Number of nephron decreases upto 56% and rate of glomerular filtration drops upto 69% leading to oliguria.
Brain : 20% of neurons die, weight decreases upto 56%, number of dendrites and axon increases to increase the number of synapse, rate of nerve conduction slows.
Sight : Presbyopia begins at the age of 40, increase in susceptibility to glare, difficulty of vision at low illumination, problem in detecting moving objects, formation of cataract.
Hearing : Difficult to detect high frequency sound waves, hearing declines more quickly in men than in women.
Skin : Loses its elasticity and develops wrinkles.
Muscle : Mass degenerate by 22% in women and 23% in men, contractility decrease (can be prevented by exercise).
Body Fat : No much loss of fat but is redistributed from below skin to deeper parts of the body. Women have more deposited in lower parts while men have more in abdominal areas.
Ageing is greatly influenced by genetic factors, diet, social and environmental conditions.
Other changes include occurrence of diseases like diabetes, atherosclerosis, arthritis etc.
Increases in cholesterol and globulin levels in blood.
Cellular Ageing
A clear mechanism is still unknown but is believed that it starts with the accumulation of worn out cell organelles and waste molecules. Due to
continuous differentiation and maturation cell loses its functional ability which ultimately leads to cell death.
Changes Include
- Chromosomal aberration and gene mutation
- Deterioration of cytoplasmic content and
- Breakdown of membranous components.
Nuclei become irregularly lobed, with condensed chromatin, dehydrated, darkly stained nucleoplasm, called as pyknotic nuclei. Distorted ER, Golgi apparatus and vacuolated mitochondria. The enzyme aldolase become more and more inactive (in liver of mice).
Extracellular Changes
Increase of interstitial collagen fibres reduces the flexibility, permeability and solubility of the tissue which obstruct the flow of nutrient and gaseous material to the cell. (Collagen theory of ageing).
