Describe the body's response to injury
HYPERTROPHY
HYPERPLASIA
ATROPHY
METAPLASIA
Enlargement of an organ or tissue > Increase in the size of its cells
Enlargement of an organ or tissue > Increase in the cell turnover rate
Reversible transformation of a fully differentiated cell into another
Wasting away of part of the body Shrinkage in cells
Cells sensitive to a particular stress are replaced by other cell types which are able to withstand stress
In cells that cannot divide (cardiac muscle) Hypertrophy is the only adaptive response
Skeletal muscle undergoes hypertrophy stimulated by increased muscle activity on exercise
Cardiac muscle undergoes hypertrophy stimulated by sustained outflow
Due to hypertension & aortic valve disease, R & L myocardium undergoes hypertrophy
Endometrium undergoes hyperplasia due to excess oestrogen exposure causing abnormal uterine bleeding
Thyroid undergoes hyperplasia in puberty & pregnancy stimulated by increased metabolic demand
Immobilization patients, loss of function causes muscle atrophy & osteoporosis
Retreat by the cell to a smaller size at which survival is still possible
In bed-bound patients reduction in blood supply causes skin atrophy (thinning) leading to pressure sores
Normal ciliated columnar epithelial cells of the trachea are replaced by the more ‘rugged’ stratified squamous ones
Cells encounter physiologic stresses
But they undergo adaptation to allow them to modulate their structure & function to escape injury
But If injury becomes irreversible, so the cell cannot recover it dies
APOPTOSIS
NECROSIS
External factors which result in the premature death of cells in living tissue by autolysis
Programmed cell death induced by activation of enzymes capable of degrading the cells’ own nuclear DNA & proteins