basallaminaan

Basal lamina, or basallamina in Dutch, is a thin, dense sheet of extracellular matrix that lies at the base of epithelial and endothelial cells and forms part of the basement membrane. It provides structural support and serves as a selective interface between cells and the underlying connective tissue.

The basal lamina is primarily composed of type IV collagen, laminin, nidogen (entactin), and heparan sulfate proteoglycans such as perlecan. These components assemble into a crosslinked network that creates a stable yet dynamic scaffold. In electron microscopy, the basal lamina is often described as having a lamina rara (electron-lucent) and a lamina densa (electron-dense) layer. It is closely associated with the reticular lamina of the connective tissue, and anchoring fibrils formed by type VII collagen help connect the basal lamina to the underlying matrix.

Location and structure: The basal lamina underlies epithelial and endothelial cells, forming a narrow boundary between these cells and the connective tissue. It is separated from the reticular lamina by a transitional zone and is linked to the underlying tissue through anchoring connections.

Functions: It supports cell adhesion, polarity, and differentiation; guides cell migration during development and wound healing; and contributes to tissue strength and filtration. In kidneys, the basal lamina of the glomerulus acts as a critical filtration barrier.

Clinical relevance: Disruption of basal lamina components can cause disease. Autoantibodies against type IV collagen can lead to Goodpasture’s syndrome; mutations in COL4A genes cause Alport syndrome; thickening or alteration of the glomerular basement membrane occurs in diabetic nephropathy. Basal lamina remodeling is also a feature of wound healing and cancer invasion.