Basaalmembranin

Basaalmembranin, commonly referred to as the basal membrane or basement membrane (and sometimes called basal lamina in some contexts), is a thin, specialized extracellular matrix that separates epithelial or endothelial cells from the underlying connective tissue. It forms a sheet at the interface between tissue compartments and provides structural support, anchoring cells to the underlying stroma.

Its extracellular matrix comprises two major components: the basal lamina, secreted by epithelial and endothelial cells, and the reticular lamina, produced by surrounding connective tissue. The basal lamina contains laminins, type IV collagen, nidogen (entactin), and heparan sulfate proteoglycans, forming a dense, hydrated network that supports filtration and cell signaling. The reticular lamina, richer in type III collagen and other matrix proteins, underlies the basal lamina in many tissues. In some descriptions, the term basement membrane is used to refer to the entire structure, while basal lamina denotes the epithelial-derived portion.

Functions of basaalmembranin include providing mechanical strength and a substrate for cell adhesion, guiding cell polarity, migration, and differentiation during development and tissue repair, and acting as a selective barrier in various organs. It plays a key role in organ architecture and in governing interactions between epithelia or endothelia and the supporting stroma. In the kidney, the glomerular basement membrane is part of the filtration barrier; in other tissues, the basal membrane underlies epithelial and endothelial layers.

Clinical relevance: defects or immune attacks against basement membranes can cause disease. Goodpasture syndrome targets glomerular and alveolar basement membranes; diabetic nephropathy often shows thickening of glomerular basement membranes; degradation of basement membranes by proteases can enable tumor invasion and metastasis.