In degenerations there is an alteration in cellular elements (metabolic or enzymatic disturbance). Some changes are reversible, some if the insult lasts a prolonged period are irreversible. Biochemical changes within a cell occur before morphological changes are visible.
Atrophy: acquired decrease in size of a portion of body, organ, tissues or individual cells.
Reduction in the size of the organ may be due to either decrease in a number of its structural units (cells) – numerical atrophy, or to the decrease in the size of the individual units – simple atrophy
Atrophy may be unaccompanied by other degenerative changes. Often fuctional parenchyma is more affected then connective tissue (relative increase).
Fat tissue replacement (pancreatic, renal tissue) – numeral atrophy
Increase pigment content (atrophied cardiac muscle) – simple atrophy
Almost all atrophy are due to changes in the nutrition and metabolism of involved cells.
Certain organs (tissues) normally undergo a reduction in size during the life time – e.g. thymus, ovarian and breast atrophy ….