Cellular Injury and Adaptation
Pathology
-Morphology : gross and microscopic changes of
cell and tissue
-Use ancillary techniques as :
Histochemical,immunohistochemical, molecular
and cytogenetics
- This will result in signs & symptoms
At the end : the pathologist will give a diagnosis and
guide therapy.
Pathology is the discipline that bridges clinical
practice and basic science
The Cell and the Environment

Cells are constantly adjusting their structure and function to
accommodate changes in their environment (stress stimuli)

Achieving a new steady state and preserving viability i.e.
ADAPTATION

if the cell adaptive capability is exceeded cell injury
develops
The Cell and the Environment
Stimuli
Cell
Adaptation
Cell Injury
Reversible
Irreversible (cell death)
apoptosis
necrosis
Causes of Cell Injury
1.
Hypoxia:



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2.
(Oxygen deficiency) Mainly due to:
ischemia (impaired blood supply) most common
inadequate oxygenation of blood (cardio-respiratory failure)
loss of oxygen carrying capacity (anaemia)
Carbon monoxide poisoning
Physical Agents
 Trauma, radiation, extremes of temperatures, electric shock
3.
Chemicals and Drugs
 Wide variety
4.
Microbiologic Agents
 Viruses, worms, bacteria …..
5.
Immunologic Reactions
 Allergic reactions, autoimmune diseases
6.
Genetic Defects
 Obvious congenital malformations (Down syndrome)
 Subtle single amino acid substitution (hemoglobin S of sickle cell anemia)
7.
Nutritional Imbalances
 Deficiency of nutrients/ or excess
8.
Aging
There are 4 main forms of Adaptation

Atrophy:
decrease in size or number of cells leading to reduction in tissue mass

Hypertrophy:
increase in size of cells leading to increase in size of organ

Hyperplasia:
increase in number of cells leading to increase size of organ

Metaplasia:
reversible change in which one adult tissue type is replaced by another
Cellular Adaptation to Injury

Physiologic


Pathologic


Responses to normal processes
Allows cells to modulate environment and hopefully
escape injury
Cellular adaptive responses can occur at any of
these Steps:

Receptor binding, signal transduction, protein
transcription, translation, export
Atrophy

Definition:
Shrinkage in the size of a cell by loss of cell
substance


Diminished cell function but cells are NOT dead
Organ Atrophy

Results when a substantial number of cells are
involved by:

Cell atrophy (cells living)
Atrophy

Causes






Decreased workload
Loss of innervations
Diminished blood supply
Inadequate nutrition
Loss of endocrine stimulation
Aging
Atrophy

Biochemical Mechanisms



Decreased protein synthesis
Increased protein catabolism (degradation)
Or/ Both
Morphology
Decreased cell size



Atrophy represents a reduction in the structural components of
the cells contain fewer mitochondria and myofilaments and a
lesser amount of endoplasmic reticulum
Increased autophagic vacuoles
Increased residual bodies (lipofuscin)
Atrophy
Normal
Kidneys,
left side normal size
right side atrophy