basalmembranen

Basalmembranen, commonly referred to as basement membranes, are thin sheets of extracellular matrix that form a specialized interface between epithelial or endothelial cells and the underlying connective tissue. They underlie all vascular and epithelial linings and surround some muscle fibers, adipocytes, and Schwann cells, helping to separate epithelium from the stroma. In mucosal tissues, the basement membrane lies just below the epithelium and above the lamina propria.

Structurally, the basement membrane comprises two closely associated layers: the basal lamina, produced primarily by epithelial or endothelial cells, and the reticular lamina, produced by the surrounding connective tissue. The basal lamina contains laminins, type IV collagen, nidogen (entactin), and proteoglycans such as perlecan; the reticular lamina contributes other collagens and matrix proteins, providing a flexible yet supportive scaffold. This composition creates a selective barrier and a signaling-rich environment that influences cell behavior.

Functions of the basement membrane include mechanical support for tissues, regulation of cell adhesion, migration, proliferation, and differentiation, and acting as a selective barrier in filtration systems. In the kidney, the glomerular basement membrane is a specialized filtration barrier essential for plasma filtration. The basement membrane also guides tissue morphogenesis during development and plays a role in wound healing and angiogenesis.

Pathological changes in basement membranes are clinically important. They can be thickened or disrupted in diseases such as diabetic nephropathy, where glomerular basement membrane thickening impairs filtration, and Goodpasture syndrome, where autoantibodies target basement membrane components. In cancer, tumor cells must breach the basement membrane to invade surrounding tissues, highlighting its role in tumor progression.