This document discusses cellular adaptive changes and injury. It describes how cells can undergo adaptive changes or lethal changes in response to various stimuli like physical or chemical agents, microorganisms, hypoxia, genetic defects, and nutritional imbalances. The types of adaptive changes cells may exhibit include accumulation of substances, changes in size or number through processes like atrophy, dysplasia, hyperplasia, hypertrophy, and metaplasia. Cellular injury can be sublethal or lethal, with lethal injury resulting in necrosis that can be coagulative or colliquative depending on how the cell structure breaks down.

1. Alterations in cell function and growth
By dr Abdiasis Omar Mohamed
MBBS

2. Cell injury and Cellular Adaptive Changes
• The life cycle of a cell exists on continuum that includes
normal activities and adaptation, injury or lethal changes.
• Adaptation is a normal life cycle adjustment like in growth
during puberty; changes during pregnancy or aging and
stressful life style produce physiologic changes that may lead
to adaptation or disease

3. • When cells are confronted to one of the following stimulus,
they may undergo adaptive changes. The common stimuli
are:-
1. Physical agents
• Trauma
• Burn
• Pressure
• Irradiation.

4. 2. Chemical agents
• Poisons, drugs, simple compounds, etc.
3. Micro organisms
• Bacteria - Virus - Fungus – Parasites
4. Hypoxia
• Is the most common stimuli (cause)
• Is because of inadequate oxygen in the blood or decreased
tissue Perfusion.

5. 5. Genetic defects
• Can affect cellular metabolism through inborn errors of
metabolism or gross malformation
6. Nutritional imbalances
• Under nutrition or over nutrition causes cellular injury or
changes.
7. Immunologic reaction E.g. – Hypersensitivity reaction.

6. • Types of cellular Adaptive-changes
• Increased concentrations of normal cellular constituents.
• Accumulate abnormal substances
• Change the cellular size or number.
• Undergo a lethal change.

7. 1. Abnormal and normal accumulation of intracellular
substances
• Cellular swelling
• Lipid accumulation (Fatty change process in the cytoplasm of
cells).
• Glycogen depositions (Excess deposition of glycogen in
organs).

8. • Calcification (precipitation of calcium in dead or Chronic
inflammation area)
• Hyaline infiltration( characteristic alteration within cells or in
the Extra-cellular spaces that appear as inclusion on stained
histology).

9. 2. Changes to cellular size or numbers(harmful agents.)
• Atrophy(decrease in cell size)
• Causes:
- Decreased work load (Disuse atrophy)
- Loss of nerve supply
- Decreased blood supply
- Inadequate nutrition

10. - Loss of hormonal stimulation Eg. (Uterine atrophy after
menopause.) (Physiologic Atrophy) Eg. - Loss of muscle bulk
with ageing.

11. • Dysplasia:- refers to the appearance of cells that have
undergone some atypical changes in response to chronic
irritation.
• It is controlled reproduction of cells, but closely related to
malignancy in that it may transform into uncontrolled, rapid
reproduction.

12. • It is complete loss of normal architectural orientation of one
cell with the next both in shape and size.
• Epithelial cells are common sites for dysplastic changes. Eg: -
Bronchial epithelium, - Cervical epithelium, etc.

13. • Hyperplasia:- increase of tissue mass due to an increase in the
number of cells.
• It occurs in cells that are under increased physiologic
workload or stimulations. I.e. the cells are capable of dividing
thus increasing their numbers.

14. • Types of Hyperplasia
1. Physiologic Hyperplasia: (hormonal stimulation) e.g.
puberty and pregnancy
2. Compensatory-Hyperplasia: (regenerating lost tissues) e.g.
liver
3. Pathologic Hyperplasia: (abnormal stimulation of organs
with cells that are capable of regeneration) e.g. Enlargement
of Thyroid gland due to TSH from pituitary gland.

15. • Hypertrophy :- increase in the size of individual cells,
resulting in increased tissue mass with out an increase in the
number of cells.
• It is usually response of a specific organ to an increased
demand for work.
• Enlargement of muscles in Athletes

16. • Metaplasia:- is a reversible change in which one type of adult
cell is replaced by another type.
• It is an adaptive substitution of one cell type more suitable to
the hostile environment for another.
• Replacement of the normal columnar, ciliated goblet cells of
the bronchial mucosa by Stratified squamous epithelial cells
in chronic smokers.

18. 3. Cellular injury and lethal changes (cell death)
• Cell injury can be sub lethal or lethal.
• Sub lethal injury alters functions with out causing cell death.
• The changes caused by this type of injury are potentially
reversible if the injuring stimuli are removed.
• Causes:-same causes of cellular adaptive changes

19. • Classification of cell injury:-
1. reversible
2. irreversible change

20. 1. Reversible cell injury:- Is cell injury which can be reversed
when the stimulus or the cause of injury is removed.
• Example -Ischemia:- Ischemia refers to a critical lack of
blood supply to a localized area (atherosclerosis) →Angina
pectoris.

21. 2. Irreversible Cell injury:-is cellular injury that can not be
corrected (reversed) after the stimulus or cause has been
removed.
• Infarction(Ischemic Necrosis):-Is localized area of tissue
death due to lack of blood supply.
• Septic Infarction(evidence of infection in the area)
• Example:- Acute myocardial infarction (AMI)

22. • Necrosis:-refers to cell or tissue death characterized by
structural evidence of this death.
- mitochondrial swelling
- rupture of cell membrane
- shrinking of nucleus or fragmenting,
- release of lysosomal enzymes, etc.

23. • Based on the structural changes, Necrosis is classified in to
two main classes:- Coagulative-Necrosis and Colliquative-
Necrosis

24. 1. Coagulative-Necrosis:- Usually results from lack of blood
supply to an area.
• The cell structure and its architectural outline is preserved,
but the nucleus is lost (structureless necrosis)
• Caseouse Necrosis(tuberculosis)

25. 2. Colliquative- Necrosis (liquefactive Necrosis):- It
frequently occurs in brain tissues and results from break down
of neurons by released lysosomal enzymes resulting in
formation of pockets of liquid, debris and cyst like structures in
the brain tissue. Example:- Wet gangrene.