ABSTRACT
Basement membranes (BM) are specialized extracellular matrix structures deposited in the close vicinity of epithelial, muscle, fat, and nerve cells. The best known example is the BM seen at the interface between the basal surface of epithelial cells and the underlying connective tissue. The term BM is used to describe different structures creating some confusion in the literature. The term BM has been used for a long time by light microscopists to denote a well visible argirophilic and periodic acid-Schiff-positive connective tissue condensation separating epithelial tissue and stromal connective tissue. BMs are considered to control a number of functions such as expression of cell phenotype, organogenesis, invasion of cells, and transport of macromolecules under normal and pathological conditions. The importance of BM explains the rapid accumulation of data about its composition, ultrastructure, and functions. The glomeral basement membrane is specialized for the filtration of blood producing protein-free filtrate of the blood plasma.
