Cell Injury, Death and Adaptation

Cell Injury, death and adaptation

Causes of Cell Injury: Hypoxia Physical agents (heat, cold, radiation, trauma) Chemical agents and drugs Microbiologic agents Immunologic reactionsGenetic defects Nutritional imbalances

Principles of Cell Injury: Dependent upon:

- the etiology- duration- severity of the inciting injury

- cell type- stage of cell cycle- cell adaptability

Cellular membranes, mitochondria, endoplasmic reticulum and the genetic apparatus are particularly vulnerable

Injury at one focus often has a cascade effect Morphologic reactions occur only after critical biochemical (molecular) damage.

Done By: Bas Dh. 2006-2007© class of 205

1

Atrophy: Acquired shrinkage in the size of the cell.physiologic : Fetus - branchial clefts - thyroglossal dust Neonate - ductus arteriosus - umbilical vessel Post adolescence - lymphoid tissue: tonsils, thymus , appendix adult - post-menopausal atrophy of the uterus, ovaries and breast.- Pathologic

localized - ischemia : e.g. cerebral atrophy due to arthrosclerosis - pressure : e.g. hydronephrosis - disuse : e.g. immobilization, obstruction of a duct draining an exocrine gland - loss of innervation : e.g. nerve damage result in atrophy of the muscles they supply - hormonal stimulation : e.g. decreased estrogen after menopause result in atrophy of the endometrium, vaginal epithelium and breast; testicular atrophy in cirrhosis, estrogen therapy etc. generalized - starvation , malnutrition - senility - hypopituitarism

Hypertrophy : An increase in the size of the cells and thus an increase in the size of the tissue

or organ[ thus, hypertrophy is seen often in those tissues that are unable to divide: their only effective response is to enlarge]

The end result is to lessen the amount of increased work that each individual cell must perform in response to the stimulation or stress

In a pure form, it is found only in muscle and is usually a response to :- increased demand for work - increased stimulation by growth hormone e.g. tongue and heart acromegaly


2

Hyperplasia : An increase in the number of cells in an organ or tissue [ thus, this response is

seen only in those tissues in which cell division can still occur] May or may not be seen in conjunction with hypertrophy Endocrine glands e.g.:

- adrenal cortex due to increased ACTH - parathyroid: primary or secondary to chronic renal failure

Endocrine target organs e.g.- breast either physiologic or pathologic - endometrium - prostate

Skin and lining epithelia : e.g. in chronic dermatitis; warts ; margins of healing ulcer

Bone marrow where there is increased demand for RBC’s


3

Cell Injury, Death and Adaptation

Documents

Transcript of Cell Injury, Death and Adaptation