Step 1: Understanding the Concept:
Tissues and organs adapt to changes in their physiological environment or workload through distinct cellular changes.
Step 2: Detailed Explanation:
Atrophy is the reduction in size of an organ, tissue, or cell after it has attained its normal mature size, often due to disease, lack of use, poor nutrition, or loss of nerve supply.
Hypertrophy is the increase in the size of cells, leading to an increase in the size of the organ.
Aplasia is the developmental failure of an organ or tissue to form.
Anemia is a reduction in red blood cells or hemoglobin.
Step 3: Final Answer:
A decrease in the size of an organ or tissue is termed atrophy.