Metabolism

The term metabolism indicates various chemical transformations that occur in living organisms. Certain reaction those are synthetic and result into the formation of larger molecules and which need energy is termed as catabolic. The changes which occur when a nutrient enters into body till it is discharged out are called as intermediating metabolism.

The diseases in which the pathogenetic mechanism involves defect in chemical transformation are categorized as metabolic disorders. Various inborn errors of metabolism and gout involve purine metabolism.

We would prefer to include under this aspect of totality some other changes in the system. Increase in acid secretion of stomach, increase or decrease in particular chemical in the body e.g. increase in cholesterol, decrease in calcium in fact chemical changes in the blood, C.S.F. etc. reflect involvement of metabolism.

Degeneration

Degeneration is rather a non-specified term as for as the pathologic terminology is concerned. For our purpose it denotes breaking down of an organized structure in to one less organized, affecting structure form and function.

Such changes start at cellular level. Two major events which give rise to degeneration at cellular a level are mitochondrial dysfunction and disturbances in membrane function. At the extreme end of it does necrosis comprise the changes that follow cell death in a living tissue or an organ. Various other changes occur which, if of sufficient magnitude, indicates degeneration e.g. alteration in organelles and cytoskeleton of the cell like heterophagy, autophagy etc.

Similarly, the adaptive responses like atrophy (decrease in cell size), hyperplasia (increase in number of cells) and metaplasia (changes in cell type) occur beyond a certain limit will come under the category of degeneration. Similar argument applies to calcification, hyaline changes and cellular aging. Intercellular accumulation of various substances like fats, proteins etc., though they are metabolic in origin, may reach a stage as to be included under degeneration.

Fibrosis involves laying down of fibrous tissue and is a common event at the end of ‘fight’ whether acute or chronic. The normal tissue, if sufficiently replaced by fibrous tissue signifies degeneration.