Cellular Adaptations for the student of paramedical

Cellular Adaptation

1. CELLULAR ADAPTATIONS

2. CONTENTS Introduction Atrophy Hypertrophy Hyperplasia Metaplasia Dysplasia Conclusion References

3. Cellular changes

4. INTRODUCTION Adaptations are reversible changes in the size, number, metabolic activity, or functions of cells in response to changes in their environment. Such adaptations may take several distinct forms. Atrophy Hypertrophy Hyperplasia Metaplasia Dysplasia

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

6. ATROPHY Atrophy may occur from physiologic and pathologic causes:

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

8. Pathological atrophy Endocrine atrophy . Ex: Hypopituitarism may lead to atrophy of thyroid, adrenal and gonads. Pressure atrophy . Ex: Erosion of spine by tumour in nerve root. Idiopathic atrophy. Ex:Testicular atrophy.

9. Atrophy Mechanism

10. HYPERTROPHY Hypertrophy is an increase in the size of parenchymal cells resulting in enlargement of the organ or tissue, without any change in the number of cells.

11. HYPERTROPHY Hypertrophy may be physiologic or pathologic Physiologic hypertrophy . Enlarged size of the uterus in pregnancy is an excellent example of physiologic hypertrophy as well as hyperplasia.

12. Pathologic hypertrophy : Hypertrophy of cardiac muscle may occur in a number of cardiovascular diseases Ex: Systemic hypertension Hypertrophy of smooth muscle Ex: Pyloric stenosis (in stomach) Hypertrophy of skeletal muscle Ex: hypertrophied muscles in athletes and manual labourers

13. Compensatory hypertrophy may occur in an organ when the contralateral organ is removed Ex. Following nephrectomy on one side in a young patient, there is compensatory hypertrophy as well as hyperplasia of the nephrons of the other kidney.

14. Hypertrophy mechanism

15. HYPERPLASIA Hyperplasia is an increase in the number of parenchymal cells resulting in enlargement of the organ or tissue. Quite often, both hyperplasia and hypertrophy occur together.

16. HYPERPLASIA Hyperplasia has also been divided into physiologic and pathologic. Physiologic hyperplasia - The two most common types follows: 1.Hormonal hyperplasia 2.Compensatory hyperplasia

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

18. Pathologic 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. Hyperplasia mechanism Cell proliferation via increased production TRANSCRIPTION FACTORS due to Increased production of growth factors Increased levels of GF receptors Activation of intracellular signaling.

20. METAPLASIA

21. METAPLASIA Metaplasia is defined as 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. Metaplasia is broadly divided into 2 types: epithelial and mesenchymal . A. EPITHELIAL METAPLASIA . Two types of epithelial metaplasia are seen squamous and columnar

22. 1. Squamous metaplasia : squamous metaplastic change due to chronic irritation that may be mechanical, chemical or infective in origin. Ex: In bronchus (normally lined by pseudostratified columnar ciliated epithelium) in chronic smokers 2. Columnar metaplasia : There are some conditions in which there is transformation to columnar epithelium. Ex: Intestinal metaplasia in healed chronic gastric ulcer

23. B. MESENCHYMAL METAPLASIA. Less often, there is transformation of one adult type of mesenchymal tissue to another. 1. Osseous metaplasia: Ex- In cartilage of larynx and bronchi in elderly people 2. Cartilaginous metaplasia. In healing of fractures, cartilaginous metaplasia may occur where there is undue mobility

24. Metaplasia Mechanism

25. DYSPLASIA It is defined as the alteration of size, shape and architectural orientation of the cellular components of the epithelium Epithelial dysplasia is characterised by histomorphologic and histopathologic changes. These changes include: Histopathologic alterations: Bulbous or teardrop shaped rete ridges. Loss of polarity keratinization or epithelial pearls. Loss of typical epithelial cohesiveness.

26. Histomorphological alterations : Enlarged nuclei and cells Large and prominent nucleoli Increased nuclear to cytoplasmic ratio Hyperchromatic nuclei Pleomorphic nuclei and cells Dyskeratosis Increased mitotic activity Abnormal mitotic figures.

27. Grades of dysplasia Mild dysplasia : Disturbance in architecture limited to the lower third of the epithelium, accompanied by minimal cytological atypia .

28. Moderate dysplasia : Disturbance in architecture extending up to the middle third of the epithelium. Alternatively lesion with mild atypical features extending in to the middle third of the epithelium. Grades of dysplasia

29. Grades of dysplasia Severe dysplasia : Recognition of severe dysplasia starts with greater than two thirds of the epithelium showing disturbance in architecture with associated with cytological atypia .

30. Grades of dysplasia Carcinoma in situ : when full thickness of epithelium shows dysplasia but the basement membrane is intact, i.e., the cells have not infiltrated through the basement membrane, it is called carcinoma in situ.

31. Conclusion Overall cellular adaptations is the changes in structure and function of cells in the human body. Thus, cellular adaptations provide clue to pathologists in diagnosing the disease.

32. References Harsh Mohan: Text Book of Pathology; 6th edition Robbins :Pathologic basis of diseases; 8th edition Colour atlas of histopathology-R.C curran 3rd edition Ak mandal :Text book of pathology Anil ghom : Text book of oral pathology Oral and maxillofacial pathology:J.Philip sapp Text book of oral pathology: Neville http://en.m.wikipedia.org>wiki>cellular_adaptaions