We had already seen that from a stimulus, the cell can respond in three ways : adaptation , reversible injury and irreversible damage . The type of injury had been discussed and now we are talking about cellular adaptation .

In the adaptation process, the cell undergoes changes in volume , in their number and in their differentiation . These changes occur due to the functional demand, hormonal stimulation, in hostile environments or genetic factors . As cellular adaptation we can cite hypertrophy, hypotrophy , hyperplasia , hypoplasia , metaplasia and dysplasia .

Hypertrophy

It is the increase of cellular constituents , namely the cell volume increase because of the increase of functional demand or hormonal stimulation. It can be classified into physiological ( eg uterine musculature at fertilization , skeletal muscle in exercise and mammary gland during lactation ) and pathological ( eg cardiac hypertrophy by the increase of blood pressure ) .

Hypotrophy

It is the opposite of hypertrophy , ie, cell has its volume reduced . It can also be physiological ( eg menopause) and pathological ( eg, decreased functional demand of a leg cast ) .

Hyperplasia

It is the increase of the number of cells because of the incresase of functional demand or hormonal stimulation. As previously mentioned , it can be physiological as the uterus and breast during pregnancy / lactation or pathological as prostate enlargement or gums.

Hypoplasia

As the suffix suggests, it is the decrease of the number of cells by the reduction of functional demand or hormones . An example of physiological is thymus hypoplasia and the redution of the number of cells of the lymphoid organs in AIDS characterize the pathological hypoplasia.

Metaplasia

In this adaptation mechanism there is a change of a tissue as an adult by another more resistant to injury . This is the case of the respiratory epithelium of smokers that is under constant assault and, thus, makes a transition to acquire resistance .

Dysplasia

It is the change in cell growth and differentiation with reduction or loss of differentiation of cells affected . This is because the more the cell proliferates , the less it differs . In this mechanism there is no invasion of the basal lamina and this is one of the characteristics that differentiates dysplasia from neoplasm .