Date post: | 25-Jan-2015 |
Category: |
Health & Medicine |
Upload: | hrudi-sahoo |
View: | 1,299 times |
Download: | 1 times |
ADAPTATION OF CELLULAR GROWTH &
DIFFERENTIATION
PRESENTED BY:Dr. Hrudi Sundar Sahoo
CONTENTS:IntroductionAdaptation of cellsMechanismsAdaptive disorders Atrophy Hypertrophy Hyperplasia Metaplasia Dysplasia
INTRODUCTION:On exposure to stress, the cells make
adjustments with the changes in their environment to:
* Physiologic needs
*Pathologic injury
ADAPTATION:PHYSIOLOGIC: Represents cells to
normal stimulation by hormones/ endogenous chemical substances.
PATHOLOGIC: The cells have the ability to modulate their environment.
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”.
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.
ADAPTIVE DISORDERS OF GROWTH:
SIZE & NUMBER:Atrophy HypertrophyHyperplasia
DIFFERENTIATION OF CELLS: MetaplasiaDysplasia
ATROPHY:Shrinkage in the size of the cell by loss of
cell substance.It represents a form of adaptive response.
CAUSES:PHYSIOLOGIC: Normal process of aging in some tissues,
which could be due to endocrine stimulation & arteriosclerosis.
Eg: Atrophy of lymphoid tissue.
CAUSES:PATHOLOGIC:Starvation atrophy- carbohydrate/fatIschemic atrophy- atrophic kidneyDisuse atrophy- atrophy of pancreaseNeuropathic atrophy- poliomyelitisEndocrine atrophy- hypopituitarismPressure atrophy- erosion of spineIdiopathic atrophy- testicular atrophy
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.
CAUSES:PHYSIOLOGIC: Enlargement of uterus
in pregnancy.
PATHOLOGIC: Hypertrophy of:
* cardiac muscle
*smooth muscle
* skeletal muscle
*compensatory hypertrophy
HYPERPLASIA:An increase in number of parenchymal
cells, which results in enlargement of organ/tissue.
CAUSES:PHYSIOLOGIC: HORMONAL:
Eg: Hyperplasia of pregnant uterus
COMPENSATORY:
Eg: Regeneratio of liver.
CAUSES:PATHOLOGIC: Occurs due to excessive stimulation of
hormones & growth factors.
Eg: Endometrial hyperplasia-following oestrogen excess.
METAPLASIA:META-TransformationPLASIA-GrowthIt 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.
CLASSIFICATION:EPITHELIAL METAPLASIA:
*Sqamous metaplasia
*Columnar metaplasia
MESENCHYMAL METAPLASIA:
*Osseous metaplasia
*Cartilaginous metaplasia
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.
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.
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.
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.
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.
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.
THANK YOU