By: Suraj Choudhary IInd B.pharm 2009-10
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Homeostasis
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The “steady state” that cell exists in normally.
An equilibrium of the cells with their environment
for adequate function.
When disturbed there is a predisposal for the onset of
pathology.
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1.
Cells adapt to changes (stimuli, stressors). Adaptations occur on a spectrum. Some are:
helpful: hypertrophy or hyperplasia increase organ size so it can
function better more harm than good. Example: increased organ size requires more blood supply. If that is not available, organ becomes ischemic 2. Adaptation can involve: change in cell size or number change to different type of cell
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On application of Stress
Stress, demand ADAPTATION
NORMAL CELL
Fails to adapt
Injurious stress
CELL INJURY CELL DEATH
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Atrophy
Metaplasia: simple columnar to
brown atrophy Hypertrophy
stratified squamous (lungs)
Dysplasia: some loss of control
as in cervix
Hyperplasia
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DEFINITION:SHRINKAGE OF CELLS CAUSES:
Physiologic due to decreased work load (e.g., decreased size of uterus following child birth, or disease) Pathologic Starvation Ischaemic Disuse Neuropathic
Endocrine Pressure Idiopathic
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Example of Atrophy
I’m Normal !
Atrophy Attack!:????
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DEFINITION: In the size of cells which results in enlargement of the
organs , without any change in the no. of cells
It is mostly seen in cells that cannot divide, such as skeletal muscle
(pumping iron), and cardiac muscle (hypertension).
These changes usually revert to normal if the cause is removed. Hypertrophy is mediated by different mechanisms. Dividing cell
Non-dividing cell
Hypertrophy + Hyperplasia Hypertrophy
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Causes of Hypertrophy
Physiologic
Enlarged size of uterus in pregnancy Action of estrogenic hormones Pathologic Hypertrophy of cardiac muscle Hypertrophy of Smooth muscle Hypertrophy of skeletal muscle Compensatory Hypertrophy
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DEFINITION: Increased number of cells in an organ or tissue. Hyperplasia may sometimes co-exist with hypertrophy. Hyperplasia can be classified as:
Physiologic--hormonal (e.g., breast and uterus during pregnancy) Compensatory--regeneration of liver following partial hepatectomy.
Various growth factors and interluekins are important in such hyperplasia.
Pathologic--excessive hormonal stimulation viral infection (papilloma
viruses); neoplasms
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Example of Hyperplasia
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DEFINITION: Transformation or replacement of one adult cell type to
another adult cell type (e.g., the change from columnar to squamous cells in respiratory tract, from squamous to columnar in Barrett esophagitis).
Metaplasia also occurs in mesenchymal tissue
(e.g., formation of bone in skeletal muscle).
Metaplastic changes usually result from chronic irritation. Metaplastic changes seem to precede the development of cancer, in
some instances.
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Types of Metaplasia
Epithelial Metaplasia
Squamous metaplasia
Columnar metaplasia
Mesenchymal Metaplasia
Osseous metaplasia
Cartilagenous metaplasia
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DYSPLASIA
The term “dysplasia” means “disordered cellular development”
It often accompanied by metaplasia & hyperplasia,thereby also referred
as Atypical Hyperplaisa
Short Duration Long Duration
Reversible Carcinoma
Cancer
It may occurs due to Chronic Irritation or Prolonged inflammation.
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Example of Dysplasia
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Key Facts
Adaptable within physiological limits. Heat Shock Proteins (HSPs):
Can respond to injury by producing cell stree proteins.
Demand met by Hypertrophy & Hyperplasia. Demand met by Atrophy.
Apoptosis :
Cell loss can be achieved from Programmed cell death
Tissue can adapt to demand by a change in differentiation known as
Metaplasia.
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