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