Andrew Ryan; Week 9 MED1011; Pathology
Physiological change can be endogenous (hormones, pregnancy) or exogenous (increased demands eg exercise, aerobic to deliver oxygen or anaerobic to deliver power). Factors influencing injury are intensity, onset, nature of injurious agent, tissue and its ability to cope. Tissue has an ability to resist injury and compensate which differs, differences when it comes to trauma, hypoxia and UV rays. Ability to regenerate also varies (labile, stable or permanent). One of the main functions of skin is to resist trauma. Stable tissue is in liver, labile on epithelia, permanent in myocardium and brain.
Reversible injury can result in resolution or adaptation, irreversible in adaptation or death. Adaptation can be at tissue level (hypertrophy, hyperplasia, atrophy or metaplasia), cellular level (increase regeneration and efficiency). Hypertrophy is increase in cell size, atrophy is decrease in cell size. Hyperplasia is increase in cell number, metaplasia is change in cell type.