This document discusses the cellular response to stress, including adaptations like hypertrophy, atrophy, hyperplasia, and metaplasia. It defines each term and provides examples of physiological and pathological types. Hypertrophy is an increase in cell size, hyperplasia is an increase in cell number, atrophy is a decrease in cell size or number, and metaplasia is the replacement of one mature cell type with another. Too much stress can lead to reversible or irreversible injury and eventually cell death if the stress cannot be adapted to.

1. By
Dr. Mayada Saad Farrag
Lecturer of Pathlogy
Faculty of Medicine

2. Welcome

3. Key Concepts
* Normal cells have a fairly narrow range of
function or steady state: Homeostasis.
• Excess physiologic or pathologic stress may
force the cell to a new steady state:
Adaptation.
* Too much stress exceeds the cell’s adaptive
capacity: Injury.

4. Adaptation
Reversible Injury
Irreversible injury
Cell Death
Normal cell
Cellular Response to Stress

5. Adaptations
It is modification of cell morphology and function
to achieve a new steady but altered state,
preserving the viability of cells, which include
1- Hypertrophy
2 –Atrophy
3- Hyperplasia
4- Metaplasia

6. Hypertrophy
- Hypertrophy is an
increase in the size
of organ by + size
of its individual
cells, in response to
a stimulus or injury.
-RNA synthesis.

7. Types
 Physiological
 Hormonal: pregnancy
 Adaptive: athletes
 Pathological
 Hormonal: Gigantism
 Adaptive: LVH
 Compensatory: paired organs

8. Hyperplasia
-Is an increase in organ size by increase of
number of its cells, in response to a
stimulus or persistent cell injury.
-DNA synthesis
-Imp:
 C/p: mass - bleeding
 Reversible
 Precancerous

9. Types
 Physiological
 Hormonal: Lactation (breast)
 Adaptive: puberty (thyroid)
 Pathological
 Hormonal: endometrial
 Irritative: epithelium
 Compensatory: hepatoctes

10. Hyperplasia
Normal adult breast
Lactating breast
Prostatic Hyperplasia

11. Atrophy
- Shrinkage in the size of organ by decrease size &/or
number of its cells
- Atrophied cells are smaller than normal but they are
still viable.

12. Atrophy
Physiologic
 General:senility
 Local:Tissues / structures present in embryo or in childhood.
Pathologic
 General: starvatin –toxic-hormonal
 Local
Disuse
Neurogenic
Ischaemic
Hormonal
Thermal
Immune
pressure

13. Atrophy,
Myocytes are thinner and less colorful than normal, due to
severe iron deficiency anemia.

14. Morphology
N/E
 General
Skin: wrinkled
Fat: exhausted
Muscles: wasted
Lung: atrophic emphysema
Bone: osteoporosis
Heart: brown atrophy
 Local: decrease size &
weight.
M/E
 Cytoplasm: reduced
 Nucleus: normal
 Intercellular spaces:
fibrous or fibrofatty
tissue.

15. Metaplasia
-A reversible change in which one mature/adult cell
type (epithelial or mesenchymal) is replaced by
another mature cell type of the same category.
- A/E: Chronic irritation- avitminosis A- genetic
- Types: Epithelial, C.T, Mesothelial

16. Epithelial metaplasia
 Causes: It is an adaptive mechanism by which the
cells less sensitive to stress are replaced by
other cell type more capable to withstand the
adverse enviroment.
 Types: - Squamous metaplasia.
- Glandular metaplasia.
- Mesothelial metaplasia.
 It may be precancerous especially epithelial
metaplasia although it is reversible

18. Barrett’s oesophagus