Basalmembrana

Basalmembrana, or basement membrane, is a thin extracellular matrix sheet that underlies epithelial and endothelial tissues and surrounds muscle, fat, and Schwann cells. It forms a continuous boundary between the epithelium and the underlying connective tissue and provides structural support and cues for cell behavior. In many tissues the basement membrane comprises two components: the basal lamina, which is closest to the epithelium, and the reticular lamina, produced by the underlying connective tissue.

The basal lamina is rich in laminin, type IV collagen, nidogen (entactin), and proteoglycans. The reticular lamina contains type III collagen and other matrix proteins produced by fibroblasts. Together they form the basement membrane, a specialized, two-layer structure that links cells to the extracellular matrix.

Functions include providing mechanical support, dividing tissue compartments, guiding cell adhesion, polarization, migration, and differentiation, and regulating filtration and permeability in organs such as the kidney. It acts as a selective barrier and as a scaffold for tissue repair after injury.

Clinical relevance: Alterations in basement membranes are seen in diabetes mellitus (thickened glomerular and capillary basement membranes), genetic disorders such as Alport syndrome (type IV collagen mutations) and Goodpasture syndrome (antibodies against basement membrane components). In cancer, basement membrane degradation allows invasion and metastasis. Understanding basement membranes informs developmental biology, nephrology, and tissue engineering.