Cellular Adaptations ability of cells to respond to various types of stimuli and adverse environmental changes Atrophy(decrease in cell size) Hypertrophy(increase in cell size) Hyperplasia(increase in cell number) Metaplasia(change in cell type): Replacement of one differentiated cell type with another mature differentiated cell type that is not normally present in that tissue. Dysplasia (increase in abnormal cell): Dysplasia is not cancer, but it may sometimes become cancer. Terminologies used in Disturbances of Cell Growth which are not adaptations Agenesis refers to the failure of an organ to develop during embryonic growth and development Hypoplasia is the underdevelopment or incomplete development of a tissue or organ. It is technically not the opposite of hyperplasia (too many cells). Hypoplasia is a congenital condition, while hyperplasia generally refers to excessive cell growth later in life. Aplasia is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process.

1. LECTURE NO 2
Cellular Response to cell Injury
Cellular Adaptations

2. Learning Outcomes
• By the end of the lecture you should be able to:
• Define Cell injury
• Enlist Cellular Response of cells
• Define and Discuss about the different types of adaptation e.g. Atrophy,
Hypertrophy, Hyperplasia, Metaplasia, Dysplasia

3. Cellular Injury
At some point, a stimulus exceeds the cell‘s ability to
adapt, causing cell injury to occur.
Cell Injury: Any change resulting in loss of the ability to
maintain the normal or adapted homeostatic state

4. Cellular Response
The cells react to an adverse influence by:
Cellular
adaptations
Atrophy,
hypertrophy,
hyperplasia etc.
Reversible cell
injury/
Degeneration
Cell Swelling
Fatty Change etc.
Irreversible cell
injury
Necrosis, Apoptosis

5. Normal Cells
Stress
Adaptation
Severe Stress
Reversible Injury Irreversible Injury
Cell death
Necrosis Apoptosis
More stress
Recovery

6. ABILITY OF CELLS TO RESPOND TO VARIOUS TYPES
OF STIMULI AND ADVERSE ENVIRONMENTAL
CHANGES
Cellular adaptation
CELLS RESPOND TO
HOMEOSTATIC CHALLENGES
THROUGH ADAPTATION

7. Cellular Adaptations
•Atrophy(decrease in cell size)
•Hypertrophy(increase in cell size)
•Hyperplasia(increase in cell number)
•Metaplasia(change in cell type): Replacement of one
differentiated cell type with another mature differentiated cell
type that is not normally present in that tissue.
•Dysplasia (increase in abnormal cell): Dysplasia is not cancer,
but it may sometimes become cancer.

9. ATROPHY
Adaptation

11. Muscle - Atrophy in a male rat from a chronic study. Individual
hypereosinophilic muscle fibers of reduced diameter are sometimes
surrounded by clear spaces.

12. Skeletal muscle - Atrophy in a male mouse from a subchronic study. Note
the reduction in myofiber diameter of the affected fibers (top) compared
with the more normal myofibers along the bottom.

13. HYPERTROPHY
Adaptation

16. Pathologic hypertrophy. Liver from a dog with enlarged hepatocytes
having increased pale, “waxy” cytoplasm (a*), due to profound increase
in smooth endoplasmic reticulum

17. Skeletal muscle - Hypertrophy in a male rat from a subchronic study.
Large, hypertrophic fibers (arrows) are adjacent to longitudinally split
muscle fibers (arrowheads).

18. HYPERPLASIA
Adaptation

19. Gingival Hyperplasia

22. Normal Endometrium

23. Hyperplasia without atypia: increase in endometrial gland to stroma ratio
with budding and complex intraluminal contours.

24. METAPLASIA
Adaptation

26. Smoking induced metaplasia in
Trachea and Bronchi

28. DYSPLASIA
Adaptation

32. Dysplasia on a Biopsy from the Uterine Cervix

34. Smoking induced cancer

35. Terminologies used in Disturbances of Cell Growth
which are not adaptations
• Agenesis refers to the failure of an organ to develop during embryonic
growth and development
• Hypoplasia is underdevelopment or incomplete development of a tissue or
organ. It is technically not the opposite of hyperplasia (too many cells).
Hypoplasia is a congenital condition, while hyperplasia generally refers to
excessive cell growth later in life.
• Aplasia is a birth defect where an organ or tissue is wholly or largely absent.
It is caused by a defect in a developmental process.