The document by Dr. Kavita Meena discusses cellular adaptation, which includes changes in cell size and number in response to environmental factors. It outlines six mechanisms of adaptation: atrophy, hypertrophy, hyperplasia, dysplasia, metaplasia, and neoplasia, each with specific definitions and examples. The conditions can be physiological or pathological, influencing normal cell function, growth, and regeneration.

1. Dr. Kavita Meena
Cell Adaptation.

2. Cell adaptation refers to
changes taking place in a
cell in response to
environmental changes.

3. Normal functioning of cell is
always threatened by many
factors such as stress
chemical agents, diseases and
environmental hazards Still,
the cell survives and
continues functioning by
means of adaptation.

4. Only during extreme conditions, cell
fails to withstand hazardous factors
which results in destructionand
death of the cell. Cellular adaptation
occurs by any of six mechanisms■

5. ATROPHY (decresend in
size)Atrophy means decrease
in size of a cell. Atrophy of a
greater number of cells
results in decreased size or
wasting of concerned tissue,
organ or part of the body.

6. Causes of Atrophy

7. i. Poor
nourishment

8. ii. Decreased
blood supply.

9. iii. Lack of workload
or exercise.

10. iv. Loss of control by
nerves or hormones.

11. v. Intrinsic disease of
the tissue or organ.

12. Types of Atrophy

13. Atrophy is of two types

14. (i) physiological
atrophy.

15. (ii)pathological
atrophy.

16. Examples of physiological
atrophy are atrophy of thymus
in childhood and tonsils in
adolescence.

17. Pathological atrophy is common
in skeletal muscle, cardiac
muscle, sex organs and brain.

18. .■2. HYPERTROPHY Hypertrophy is
the increase in size of a cell.
Hypertrophy of many cells results in
enlargement or overgrowth of an organ
or a part of the body.

19. Hypertrophy is of three types
1.Physiological Hypertroph
Physiological hypertrophy is the increase
in size due to increased workload or
exercise. Common physiological
hypertrophy includes:

20. Muscular hypertrophy: Increase
in bulk of skeletal muscles that
occurs in response to strength
training exercise. II. Ventricular
hypertrophy: Increase in size of
ventricular muscles of heart. It is
advantageous only if it occurs in
response to exercise.

21. 2. Pathological Hypertrophy
Increase in cell size in response to
pathological changes is called
pathological hypertrophy.

22. *Example is the ventricular
hypertrophy that occurs due
to pathological conditions
such as high blood pressure,
where the workload of
ventricles increases.

23. 3. Compensatory Hypertroph
Compensatory hypertrophy is the
increase in size of cells of an organ
that occurs in order to compensate
the loss or dysfunction of another
organ of same type.

24. *Examples are hypertrophy of one
kidney when the other kidney
stops functioning and the increase
in muscular strength of an arm
when the other arm is
dysfunctional or lost.

25. 3. HYPERPLASIA Hyperplasia is
the increase in number of cells due
to increased cell division
(mitosis). Hyperplasia results in
enlargement of the organ. It
involves increased division of
normal cells only.

26. Hyperplasia is of three types
1.Physiological Hyperplasi
Physiological hyperplasia is the
momentary adaptive response to
routine physiological changes in
the body.

27. *Example, during proliferative phase
of each menstrual cycle, the
endometrial cells in uterus increase in
number.

28. 2. Compensatory
Hyperplasia

29. It is the increase in number of
cells in order to replace the
damaged cells of an organ or
the cells removed from the
organ. It helps the tissues and
organs in regeneration.

30. It is common in liver. After surgical
removal of damaged part of liver,
there is increase in number of liver
cells resulting in regeneration.
Compensatory hyperplasia is also
common in epithelial cells of
intestine and epidermis.

31. 3. Pathological hyperplasia

32. It is the increase in number
of cells due to abnormal
increase in hormone
secretion.

33. It is also called
hormonal hyperplasia.

34. * Example, in gigantism,
hypersecretion of growth
hormone induces hyperplasia
that results in overgrowth of
the body.

35. 4. DYSPLASIA Dysplasia is the
condition characterized by
abnormal change in size, shape
and organization of cell.

36. It is not considered as true
adaptation and it is suggested as
related to hyperplasia. It is common
in epithelial cells of cervix and
respiratory tract.

37. 5.METAPLASIA

38. Metaplasia is the condition
that involves replacement of
one type of cell with another
type of cell. It is of two types.

39. 1. Physiological Metaplasia It is the
replacement of cells in normal
conditions. Examples are
transformation of cartilage into bone
and transformation of monocytes
into macrophages.

40. 2. Pathological Metaplasia Pathological
metaplasia is the irreversible replacement
of cells due to constant exposure to
harmful stimuli. For example, chronic
smoking results in transformation of
normal mucus secreting ciliated columnar
epithelial cells into non-ciliated squamous
epithelial cells, which are co incapable of
secreting mucus. These transformed cells
in may become cancerous cells if the
stimulus is prolonged.

41. ■6. NEOPLASM OR TUMOR
Neoplasm or tumor is abnormal
growth of any tissue or organ in the
body. Neoplasm may be benign (non-
cancerous) or malignant
(cancerous).

42. Thank you
*****************
Dr. Kavita Meena
Department of
physiotherapy