Basal lamina scaffold-anatomy and significance for maintenance of orderly tissue structure.

The basal lamina is an extracellular scaffold positioned between parenchymal cells and connective tissue. Parenchymal cells attach to one of its surfaces and the other is anchored to connective tissue. By its presence it defines the spatial relationships among similar and dissimilar types of cells and between these cells and the space occupied by connective and supportive tissues. Replenishment of cells which have died during normal functioning or have become damaged in course of injury occurs with new cells in an orderly way along the framework of the basal lamina scaffold. This process appears to be aided by the polarity of the basal lamina and by an apparent specificity for cell types, and it enables multicellular organisms to reconstitute histologic structures of most tissues and organs to what they were prior to loss of cells. If the basal lamina is destroyed, the healing in most tissues results in formation of scar and loss of function. The properties of the basal lamina concerned with maintenance of histologic order in organs and tissues offer new ways to interpret the pathogenesis of several common disorders, including emphysema, scars, adhesions, cirrhosis of liver and excessive accumulation of basal lamina material as, for example, it occurs in patients with diabetes mellitus.