Growth disturbances, Cellular adaptation and reversible cell injury

1. Dr. A K M Maruf Raza
Associate Professor of Pathology
Based on Robbins and Cotran
9th edition
Item No. 02
Growth disturbance, adaptive
changes and Reversible cell
injury

2. Cellular response to stress and
injurious stimuli
• A normal cell handle physiologic demands and
maintain a steady state which is called
Homeostasis.
• Cells constantly undergo adaptation to the changes
in their environment.
• The adaptation allows cell to survive and continue
to function in the altered environment.

3. Cellular response to stress and
injurious stimuli
• In altered environment cells undergo functional
and structural changes called Cellular Adaptation.
• The cellular adaptation is a reversible state.
• When the adverse environment is eliminated cells
recover to its original state.

4. Cellular Adaptation
• Adaptations are reversible changes in the size,
number, phenotype, metabolic activity or
functions of cells in response to changes in their
environment..
• When the stress is eliminated the cell recover to its
original state.

5. What are the altered environment
and injurious stimuli?
• Increased demand to increase functional capacity of
a cell.
• Increased stimulation by growth factors, hormones.
• Decreased nutrients
• Decreased nerve stimulation
• Chronic irritation (physical or chemical)

6. Cellular response to stress and
injurious stimuli

7. Cellular Adaptations types
• Hypertrophy
• Hyperplasia
• Atrophy
• Metaplasia

8. Hypertrophy
• Hypertrophy refers to an increase in the size of
cells, that results in an increase in the size of the
affected organ.
• The hypertrophied organ has no new cells, just
larger cells.
• Hypertrophy occurs in non dividing cells (cardiac
muscle).

9. Hypertrophy of Uterus During Pregnancy

10. Hypertrophy of Uterine muscle in Pregnancy
No new cells; Cells just bigger

11. Causes of Hypertrophy
• Hypertrophy occurs usually due to increased
demand.
• In hypertrophy there is increased production of
cellular proteins.
• Hypertrophy can be physiologic or pathologic.

12. Causes of Hypertrophy
Physiologic hypertrophy:
i. Hypertrophy of pregnant uterus
ii. Hypertrophy of skeletal muscle of body
builders
Pathological hypertrophy: Hypertrophy of cardiac
muscle in chronic circulatory overload resulting to:
i. Left Ventricular Hypertrophy
ii. Right Ventricular Hypertrophy

13. Pathological hypertrophy
Myocardium in hypertensive heart disease
LV=left ventricle

14. Hyperplasia
• Hyperplasia is the increase in the number of cells
in an organ or tissue.
• Cells capable of division may undergo both
hyperplasia and hypertrophy.
• Hyperplasia can be physiologic or pathologic.

15. Physiologic Hyperplasia
1. Female breast at puberty and in pregnancy.
2. Uterus in pregnancy.
3. Liver after partial hepatectomy.

16. Pathologic Hyperplasia
• Endometrial hyperplasia due to excess estrogen
hormonal stimulation.
• Prostatic hyperplasia / Nodular hyperplasia of
prostate in old age male.

17. Nodular hyperplasia of prostate
From a young man
showing uniform
texture of gland
From an elderly man
showing irregular
hyperplastic nodules.
This would cause
obstruction

18. Atrophy
• Atrophy is decrease in cell size and cell number
resulting in reduction in the size of an organ or
tissue.
• Atrophy can be physiologic or pathologic.

19. Physiologic atrophy
• Notochord and thyroglossal duct undergo atrophy
during fetal development.
• Atrophy of Uterus shortly after giving birth.

20. Pathologic atrophy
• Decreased workload (atrophy of disuse).
• Loss of innervation (denervation atrophy).
• Diminished blood supply (senile atrophy).
• Inadequate nutrition (cachexia).
• Loss of endocrine stimulation (Reproductive organs).
• Pressure atrophy.

21. Muscle atrophy

22. Metaplasia
• Metaplasia is a reversible change in which one
differentiated cell type is replaced by another
differentiated cell.
• Metaplasia is an adaptive change but also a fertile
soil for malignancy.
• Metaplasia is called a two edged sword.

23. Types of Metaplasia
i. Epithelial metaplasia.
ii. Connective tissue metaplasia.
• Epithelial metaplasia: Types:
i. Squamous metaplasia.
ii. Columner metaplasia.
• Connective tissue metaplasia:
Metaplasia occurs in connective tissue.
Bone formation in muscle (myositis ossificans).

24. Metaplasia
• Squamous metaplasia: Metaplasia from columnar
to squamous cell:
Respiratory tract ciliated columnar
epithelium is replaced by squamous cells due
to chronic irritation like cigarette smoking.
• Columner metaplasia: Metaplasia from squamous
to columnar cell:
Esophageal squamous epithelium is replaced by
columnar epithelium (Barrett esophagus).

25. Columnar cells replaced by squamous cells
Squamous Metaplasia

26. Metaplasia is a fertile soil for malignancy
• During metaplasia one cell type is replaced by
another cell type from the reserve cells.
• During this transformation there is chance of
change in the DNA (mutation).
• If that mutation is not corrected, the cell may
undergo malignant transformation (Cancer).

27. Metaplasia is a two edged sword
• During metaplasia one cell type is replaced by
another cell type.
• So in one hand that transformed cell can not
perform function of previous cell type.
• And in other hand there is a chance of malignancy
(mutation) in this process of transformation.
• Example is in respiratory tract metaplasia.

28. Cell Injury

29. Cell Injury
• If the limits of adaptive responses are exceeded or
if cells are exposed to injurious agents or stress,
deprived of essential nutrients that affect essential
cellular constituents, a sequence of events follows
that is termed cell injury.

30. Cell Injury
• Cell injury is reversible up to a certain point, but if
the stimulus persists or is severe enough, the cell
suffers irreversible injury and ultimately undergoes
cell death.

31. Cellular response to injury

32. Cellular response to injury
• Adaptation.
• Cell injury:
i. reversible, ii. Irreversible injury
• Intratcellular acumulations, Calcifications.
• Cellular ageing.

33. Causes of Cell Injury
• Oxygen Deprivation (Hypoxia and ischemia)
• Physical Agents (mechanical trauma, extremes of
temperature (burns and deep cold), radiation,
electric shock).
• Chemical Agents and Drugs (arsenic, cyanide,
insecticides, even oxygen in high concentration).

34. Causes of Cell Injury
• Infectious Agents (bacteria, virus, fungus).
• Immunologic Reactions (autoimmune diseases).
• Genetic abnormality (Down syndrome).
• Nutritional Imbalances (Protein-calorie
deficiencies, Obesity).

35. Types of cell injury
1. Reversible cell injury:
i. Cellular swelling
ii. Fatty change
2. Irreversible cell injury:
i. Necrosis
ii. Apoptosis

36. Reversible cell injury:
i. Cellular Swelling.
ii. Fatty Change.
• Fatty change is manifested by the appearance of
lipid vacuoles in the cytoplasm. Fatty change
affects liver, Heart, kidneys.

37. Reversible Injury: What are the changes?
– Changes not seen in light microscope.
Ultrastructural changes seen in electron
microscope:
i. Plasma membrane blebbing and loss of
microvilli.
ii. Mitochondrial swelling.
iii. Dilation of endoplasmic reticulum with
detachment of ribosomes.

38. Reversible Injury

39. Reversible injury: Fatty Change of liver