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

Welcome

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.

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

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

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.

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

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

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

Hyperplasia
Normal adult breast
Lactating breast
Prostatic Hyperplasia

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.

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

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

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.

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

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

Barrett’s oesophagus