Atrophy & Hypertrophy

Atrophy

Atrophy is the decrease in size of an organ that have formerly reached its full size.

It may occur by two ways-

1.      Numerical atrophy that is caused by death of cells and

2.      Quantitative atrophy that is caused by decrease in size of cells.

Etiology

• Physiological, e.g., senile atrophy,

• Pressure atrophy,

• Disuse atrophy e.g. Atrophy of immobilized legs,

• Hormonal, e.g., atrophy of testicles,

• Environmental pollution, e.g., atrophy of lymphoid organs,

• Inflammation/ fibrosis.

Macroscopic features

•      Size, weight and volume of the organ is reduced.

Microscopic features

•      Size of cells is reduced.

•      Number of cells is decreased.

•      Wrinkles in capsule of organ are present.

•      More fat and connective tissue is present.

Hypertrophy

Hypertrophy is the increase in size of cells leading to increase in size of organ than normal without increase in the number of cells.

Etiology

•      Increase in metabolic activity, e.g., enlargement of myometrium during pregnancy or enlargement of mammary gland before the onset of lactation (Hormonal hypertrophy).

•      Enlargement of skeletal muscle due to repeated exercise/ loss of a kidney may lead to enlargement of the other kidney (Compensatory or adaptive hypertrophy).

Macroscopic features

•      Size, weight and volume of the organ is increased.

Microscopic features

•      Size of cells is increased.