A specialized form of extracellular matrix that underlies the basal side of polarized epithelial cell sheets to separate them from the underlying connective tissue . Basal laminae (plural) also surround individual muscle cells, fat cells, and cells lining peripheral nerve cell axons (i.e. Schwann cells) . The basal lamina is thin and flexible, and is composed of closely packed matrix molecules that lack significant volume. The basal lamina components are synthesized and deposited by the cells on either side: the epithelial cells and the cells within the underlying bed of connective tissue (i.e. fibroblasts). The basal laminae forms a cohesive network and mechanical connection between cells and their external environment. Force-driven signals originating between the basal lamina components (i.e. fibronectin) and linked cell adhesion receptors (i.e. integrins) is communicated to the interior of cells through a mechanotransduction system to influence cell polarity, metabolism, fate, and migration.
The key constituents found in the basal lamina are glycoproteins (i.e. laminin, collagen) and proteoglycans (i.e. perlecan), however, the precise composition varies from tissue to tissue and various other molecules (e.g. fibronectin) can also be found .