This document discusses different types of cell adaptations: atrophy, hypertrophy, hyperplasia, and metaplasia. Atrophy is a decrease in cell size and number. Hypertrophy is an increase in cell size due to increased functional demand or stimulation by hormones. Hyperplasia is an increase in cell number through cell division. Metaplasia is a reversible change where one cell type replaces another through reprogramming of precursor cells.

1. Cell Adaptations
By Dr. Amnah Shaukat

2. Introduction:

3. Introduction:

4. Causes of Cell Injury:
Hypoxia (oxygen deficiency)
Physical Agents
Chemicals
Infections
Immunological Reactions
Genetic Errors
Nutritional Imbalances

5. Cell Adaptations:
1. Atrophy
2. Hypertrophy
3. Hyperplasia
4. Metaplasia

6. 1. Atrophy:
Decrease in the number and
size of the cells of an organ
Mechanism :Decreased protein
synthesis and increased protein
degradation in the cells

7. 1. Atrophy:

8. 1. Atrophy:

9. 2. Hypertrophy:
Increase in the SIZE of the
parenchymal cells in the organ
 Cause : Increased functional
demand or by stimulation of
hormones and growth factors
Mechanisms : Increased production
of cellular proteins.

10. 2. Hypertrophy:

11. 2. Hypertrophy:

12. Atrophy VS Hypertrophy:

13. 3. Hyperplasia:
Increase in the NUMBER of cells in an
organ
It takes place if the cell population is
capable of dividing
Mechanism :
Results from growth factor induced
proliferation of mature cells or
Increased output of new cells from stem cells.

15. 3. Hyperplasia:

16. Hypertrophy VS Hyperplasia:

17. 4. Metaplasia:
It is a reversible change in which one
differentiated cell type (epithelial or
mesenchymal) is replaced by another
cell type
Mechanism: Due to
REPROGRAMMING of the precursor
cells, present in the normal tissues.

18. 4. Metaplasia: