Basement membrane

A thin, specialized extracellular matrix layer beneath epithelial cells that anchors them and separates them from underlying connective tissue.

Basal lamina: The extracellular layer of a basement membrane formed mainly by epithelial cells and containing laminin and type IV collagen. It is the epithelial-facing layer that gives the basement membrane much of its structure.
Integrin: A family of cell-surface receptors that connects extracellular matrix proteins to the cytoskeleton. Integrins anchor epithelial cells to basement-membrane proteins and relay mechanical signals.
Glomerular basement membrane: The basement membrane between glomerular endothelial cells and podocytes in the kidney. Its selective permeability is essential to filtering blood while retaining most plasma proteins.
Reticular fibers: Fine collagen fibers, mainly type III collagen, that form supportive networks in many tissues. They belong to connective-tissue networks rather than the basement membrane’s type IV collagen sheet.
Reticular lamina: The connective-tissue-facing layer beneath the basal lamina, rich in collagen fibers. It links the epithelial basement membrane to the underlying connective tissue.
Hemidesmosome: A cell junction that anchors epithelial cells to the basement membrane through intermediate filaments. It provides a strong mechanical attachment to the membrane.
Alport syndrome: An inherited disorder caused by defects in type IV collagen that damages kidney, ear, and eye tissues. Abnormal basement membrane collagen disrupts the kidney filtration barrier.
Interstitial matrix: The extracellular matrix filling spaces between cells in connective tissues and organs. Unlike the basement membrane’s thin, organized sheet, it forms a broader three-dimensional tissue network.
Laminin: A family of extracellular matrix proteins that bind cell receptors and organize basement membrane networks. Laminin helps connect epithelial cells to the basement membrane’s structural network.
Focal adhesion: A dynamic cell–matrix junction linking integrins to actin filaments and intracellular signaling proteins. Unlike hemidesmosomes, focal adhesions connect matrix attachment to actin and are highly dynamic.

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