Cell adaptation.....................pptx

1. Cell adaptation Dr. Aebeena B abu Oral Pathology

2. Overview: cellular responses to stimuli and noxious stimuli Stress Injurious stimulus Mild, transient Inability to adapt Severe, progressive CELL DEATH NORMAL CELL (homeostasis) REVERSIBLE INJURY ADAPTATION CELL INJURY IRREVERSIBLE INJURY APOPTOSIS NECROSIS

3. ADAPTATION OF CELLULAR GROWTH AND DIFFERENTIATION Adaptation are reversible changes in the size, number , phenotype, metabolic activity, or functions of cell in response to their environment (Robbin’s and cotran pathologic basis of disease 7 th edition)

4. Types of cell adaptation Hypertrophy (increase in size of cells and functional activity) Hyperplasia (increase in number) Atrophy (decrease In size and metabolic activity of cells) Metaplasia (change in phenotype of cells)

5. HYPERTROPHY

6. HYPERTROPHY Hypertrophy refers to an increase in the size of cells, Resulting in an increase in the size of the organ Due to the synthesis of more structural components of the cells Example : Muscular hypertrophy in response to exercise .

7. HYPERTROPHY HYPERTROPHY PATHOLOGICAL PHYSIOLOGICAL

8. PATHOLOGICAL HYPERTROPHY Hypertrophy of cardiac muscle which occurs in cardiovascular diseases Example: S ystemic hypertension Aortic valve disease Mitral insufficiency Hypertrophy of smooth muscle example: Pyloric stenosis(in stomach) cardiac achalasia(in oesophagus ) Hypertrophy of skeletal muscle Example: hypertrophied muscles in athletes and manual laborers

9. Compensatory hypertrophy : occur in an organ when the contralateral organ is removed Example : Adrenal hyperplasia following removal of one adrenal gland

10. PHYSIOLOGICAL HYPERTROPHY Enlarged size of the uterus in pregnancy is an excellent example of physiologic hypertrophy as well as hyperplasia

11. HYPERTROPHY MECHANISM

12. in mechanical stretch agonist Growth (increased work load ) ( eg : α -adrenergic hormones,angiotensin ) factors Signal transduction pathway Transcription factors( Myc,Fos,Jun,Others ) Induction of embryonic/fetal genes(e.g. cardiac Increase Synthesis of contractile proteins Increase production of growth factors Increase mechanical performance Increase Mechanical performance Decrease work load

13. HYPERPLASIA

14. HYPERPLASIA Hyperplasia is an increase in the number of parenchymal cells resulting in enlargement of the organ or tissue. Both hyperplasia and hypertrophy occurs together

15. HYPERPLASIA PATHOLOGICAL PHYSIOLOGICAL

16. PHYSIOLOGICAL HYPERPLASIA Physiological hyperplasia is divided into two types: 1) Hormonal hyperplasia 2) Compensatory hyperplasia

17. 1 ) Hormonal hyperplasia : hyperplasia occurring under the influence of hormonal stimulation Ex: Hyperplasia of female breast at puberty, during pregnancy and lactation 2) Compensatory hyperplasia: hyperplasia occurring following removal of part of an organ or a contralateral organ in paired organ ex: Regeneration of the liver following partial hepatectomy

18. P athologic hyperplasia : pathologic hyperplasia are due to excessive stimulation of hormones or growth factors. Ex : In wound healing, there is formation of granulation tissue due to proliferation of fibroblasts and endothelial cells

19. MECHANISM OF HYPERPLASIA Is the result of growth factor –driven proliferation of mature cells Increased output of new cells from tissue stem cells After some minor hepatic injury ,liver cells regenerate under the influence of certain growth factors But if regenerative capacity of hepatocyte is comprised( eg : in hepatitis) ,hepatocyte can instead regenerate from intrahepatic stem cells

20. METAPLASIA

21. METAPLASIA Definition: A reversible change of one type of epithelial or mesenchymal adult cells to another type of adult epithelial or mesenchymal cells, usually in response to abnormal stimuli, and often reverts back to normal on removal of stimulus.

22. METAPLASIA EPITHELIAL METAPLASIA MESENCHYMAL METAPLASIA SQUAMOUS COLUMNAR OSSEOUS CARTILAGINOUS

23. EPITHELIAL METAPLASIA Squamous metaplasia : change due to chronic irritation that may be mechanical, chemical, or infective in origin ex: in bronchus (lined by pseudostratified columnar ciliated epithelium) in chronic smokers Columnar metaplasia: condition in which there is transformation to columnar epithelium ex: intestinal metaplasia in healed chronic gastric ulcer

24. MESENCHYMAL METAPLASIA Osseous Metaplasia: Ex –In cartilage of larynx and bronchi in elderly people Cartilaginous metaplasia: Ex: In Healing Fractures

25. METAPLASIA MECHANISM Reprogramming of stem cells that are known to exist in normal tissues, or of undifferentiated mesenchymal cells present in connective tissue The precursor cells differentiate along a new pathway Brought by a signals generated by cytokines ,growth factors and extracellular matrix components in the cells environment

26. ATROPHY Reduction of the number and size of parenchymal cells of an organ or its parts which was o nce normal is called atrophy

27. Atrophy may occur from physiologic and pathologic causes PHYSIOLOGIC ATROPHY : Atrophy of brain with aging Atrophy of gonads after menopause

28. PATHOLOGIC ATROPHY Starvation atrophy Ischemic atrophy Disuse atrophy Neuropathic atrophy Endocrine atrophy Pressure atrophy Idiopathic atrophy

29. Pathological atrophy Starvation atrophy : In starvation, there is first depletion of carbohydrates and fat stores followed by protein catabolism. Ischemic Atrophy : Ex : atrophy of brain in cerebral atherosclerosis Disuse atrophy : Ex: Atrophy of the pancreas in obstruction of pancreatic duct Neuropathic atrophy : Ex: poliomyelitis

30. Endocrine atrophy : Ex: Hypopituitarism may lead to atrophy of thyroid , adrenal and gonads Pressure atrophy : Ex: erosion of spine by tumor in nerve root Idiopathic atrophy : Ex: T esticular atrophy

31. ATROPHY MECHANISM Decreased protein synthesis and increased protein degradation in cells Activates ubiquitin proteosome pathway increased autophagy(self eating) results in no. of autophagic vacuoles Autophagic vacuoles containing cell organelles are formed They fuse with lysosomes and organelles are digested

32. CONCLUSION Cell adaptation is the changes in structure and function of the cells in the human body. Cell adaptation provide a clue to pathologist in diagnosing the disease