1. Cellular Adaptations of Growth and Differentiation
Dr. Abdulmalik Alsheikh,MD, FRCPC

2. Cellular Adaptations of Growth and Differentiation
Introduction
Adaptations
Hyperplasia
Hypertrophy
Atrophy
Metaplasia

3. Hyperplasia
Definition : an increase in the number of cells in an organ or tissue.
It is possible only if cells are capable of synthesizing DNA and mitotic division.
Types :
Physiologic
pathologic

4. Hyperplasia Physiologic Hyperplasia: Hormonal Hyperplasia:
increases the functional capacity of the tissue
Breast during pregnancy and lactation
Pregnant uterus
Compensatory Hyperplasia:
Increases tissue mass
Liver after partial hepatectomy

5. growth factors acting on target cells
Hyperplasia
Pathologic Hyperplasia:
caused by excessive :
hormonal stimulation or
growth factors acting on target cells

6. Hyperplasia Pathologic Hyperplasia: Hormonal :
Endometrial hyperplasia:
Increased Estrogen
Progesterone/Estrogen imbalance
Benign prostatic hyperplasia:
Androgens

7. Hyperplasia Pathologic Hyperplasia Growth Factors Stimulation
Skin wart due to viral effect :
Human Papilloma Virus ( HPV ) .

8. Hyperplasia IS IT REVERSIBLE ? IS IT PREMALIGNANT ? YES
NO…..BUT….PATIENT IS AT INCREASED RISK TO DEVELOP CANCER
Good environment !!
Endometrial hyperplasia

9. Hypertrophy
Definition : an increase in the size of cells and consequently an increase in the size of the organ.
Due to synthesis of more structural components
NO NEW CELLS!! ONLY BIGGER

10. Hypertrophy Types : Causes : Physiologic Pathologic
Hormonal Stimulation
Increased functional demand

11. Hypertrophy Physiologic : Gravid uterus Muscle mass in athletes
Both hypertrophy and hyperplasia of smooth muscle.
Muscle mass in athletes
hypertrophy

12. W. B. Saunders Company items and derived items Copyright (c) 1999 by W
W.B. Saunders Company items and derived items Copyright (c) 1999 by W.B. Saunders Company
Slide 2.3

13. Hypertrophy Pathologic :
Cardiac muscle hypertrophy: due to chronic hemodynamic overload
Hypertension - cardiac muscle hypertrophy due to increased resistance !!
Cardiac valves diseases

14. Cardiac and skeletal muscle cannot divide
Remember!!
Cardiac and skeletal muscle cannot divide

15. Atrophy Remember ….atrophic cells are not dead !!
Definition : Shrinkage in the size of the cell by the loss of cell substance.
If sufficient number of cells is involved, the entire organ/tissue will decrease in size ….ATROPHIC.
Remember ….atrophic cells are not dead !!

16. Atrophy Physiologic or Pathologic Physiologic: Pathologic:
Some embryonic strucrures during fetal development
Uterus after delivery
Pathologic:
Local
generalized

17. Atrophy Causes : Decreased workload Loss of innervation
Decreased blood supply
Inadequate nutrition
Loss of endocrine stimulation
Aging
Pressure

18. Atrophy Normally ….Synthesis = Degradation Atrophy….
Decreased synthesis and/or increased degradation

19. W. B. Saunders Company items and derived items Copyright (c) 1999 by W
W.B. Saunders Company items and derived items Copyright (c) 1999 by W.B. Saunders Company
Slide 2.5

20. Metaplasia
Definition : a reversible change in which one adult cell type ( epithelial or mesenchymal ) is replaced by another adult cell type.
Can occur in epithelial or mesenchymal tissues

21. Metaplasia WHY ?!! It is an adaptation process.
Sensitive cells are replaced by other cells which more capable to withstand ( tolerate ) the adverse environment.
Examples:
Smoker lung
Barrett’s esophagus

22. W. B. Saunders Company items and derived items Copyright (c) 1999 by W
W.B. Saunders Company items and derived items Copyright (c) 1999 by W.B. Saunders Company
Slide 2.6

23. Slide 2.7

24. Metaplasia Mechanism Is it good or bad ?!!
Stem cells/ undifferentiated cells
Reprogramming
Is it good or bad ?!!
Stimuli that predispose to metaplasia , if persistent, may induce malignant transformation in the metaplastic epithelium