Ageing Theory

No one knows how and why people change as they get older. Some theories claim that ageing is caused by injuries from ultraviolet light over time, wear and tear on the body, or byproducts of metabolism. Other theories view ageing as a predetermined process controlled by genes.






Cells shrink. If enough cells decrease in size, the entire organ atrophies. This is often a normal ageing change and can occur in any tissue. It is most common in skeletal muscle, the heart, the brain, and the sex organs (such as the breasts).



Cells enlarge. This is caused by an increase of proteins in the cell membrane and cell structures, not an increase in the cell’s fluid. When some cells atrophy, others may hypertrophy to make up for the loss of cell mass.


The number of cells increases. There is an increased rate of cell division. Hyperplasia usually occurs to compensate for a loss of cells. It allows some organs and tissues to regenerate, including the skin, lining of the intestines, liver, and bone marrow. The liver is especially good at regeneration.







The formation of tumors, either cancerous (malignant) or noncancerous (benign). Neoplastic cells often reproduce quickly. They may have unusual shapes and abnormal function.
