3. INTRODUCTION:
On exposure to stress, the cells make
adjustments with the changes in their
environment to:
* Physiologic needs
*Pathologic injury
4. ADAPTATION:
PHYSIOLOGIC: Represents cells to
normal stimulation by hormones/
endogenous chemical substances.
PATHOLOGIC: The cells have the
ability to modulate their environment.
5. SURVIVAL OF THE FITTEST:
Adaptive responses are reversible on
withdrawal of stimulus.
If the irritant / stimulus persists for a longer
time cell may not be able to survive.
Thus, the concept of evolution “ survival
of fittest” holds true for adaptation as
“survival of adaptable”.
6. MECHANISM:
Altered cell surface receptor binding.
Alterations in signal for protein synthesis.
Synthesis of new proteins by the target
cell such as heat-shock proteins.
9. ATROPHY:
Shrinkage in the size of the cell by loss of
cell substance.
It represents a form of adaptive response.
10. CAUSES:
PHYSIOLOGIC:
Normal process of aging in some tissues,
which could be due to endocrine
stimulation & arteriosclerosis.
Eg: Atrophy of lymphoid tissue.
12. HYPERTROPHY:
An increase in the size of the cells, which
results in enlargement of organ without
any changes in the number of cells.
Occurs due to incresed functional demand
& hormonal stimulation.
14. HYPERPLASIA:
An increase in number of parenchymal
cells, which results in enlargement of
organ/tissue.
15. CAUSES:
PHYSIOLOGIC:
HORMONAL:
Eg: Hyperplasia of pregnant uterus
COMPENSATORY:
Eg: Regeneratio of liver.
16. CAUSES:
PATHOLOGIC:
Occurs due to excessive stimulation of
hormones & growth factors.
Eg: Endometrial hyperplasia-following
oestrogen excess.
17. METAPLASIA:
META-Transformation
PLASIA-Growth
It is a reversible change of one type of
epithelial or mesenchymal cells, usually in
response to persistant abnormal stimulus
which in turn may change into a
malignant cell.
19. EPITHELIAL METAPLASIA:
The most common type.
Metaplastic change cane either patchy or
diffuse.
Leads to alterations in the epithelium.
Deprivation of protective mucous secretion.
More prone to infection.
20. TYPES:
SQAMOUS METAPLASIA:
Occurs due to chronic irritation
(chemical/mechanical/infective)
Eg: Bronchus in chronic smokers.
COLUMNAR METAPLASIA:
Eg: Intestinal metaplasia in healed
chronic gastric ulcer.
21.
22. MESENCHYMAL
METAPLASIA:
Less often there is transformation of one
type of mesenchymal tissue to another.
OSSEOUS: Formation of bone in fibrous
tissue, cartilage & myxoid tissue.
Eg: In arterial wall in old people.
CARTILAGENOUS: In healing of
fractures, where there is undue mobility.
23. DYSPLASIA:
Disordered cellular development often
accompanied with metaplasia & hyperplasia
(ATYPICAL HYPERPLASIA).
Occurs most often in epithelial cells, which is
characterised by cellular proliferation & cytologic
changes.
24.
25.
26. CAUSES:
Occurs due to chronic irritation or
prolonged inflammation.
On removal of simulus, the changes may
disappear.
In majority of cases dysplasia progresses
into carcinoma insitu or invasive cancer.
27. CHANGES:
Increased number of layers of epithelial
cells.
Disorderly arranged cells.
Loss of basal polarity.
Cellular & nuclear pleomorphism.
Increased nucleocytoplasmic ratio.
Nuclear hyperchromatism.
Increased mitotic activity.