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basal lamina

noun

1. (cell biology) a layer of extracellular matrix found on the basal surface of epithelial cells, and which is secreted by the epithelial cells.

It is composed of electron-dense layer called lamina densa (composed of type IV collagen) and electron-lucid layers called lamina lucida (made up of laminin, integrins, entactins, and dystroglycans) together make up the basal lamina.

The term "basal lamina" is usually used with electron microscopy, while the term "basement membrane" is usually used with light microscopy. That is because basal lamina is readily visible as distinct structure with the electron microscope, and not with a light microscope.

In strict sense, basal lamina is different from basement membrane based on their components. The basal lamina is composed of lamina densa and lamina lucida whereas the basement membrane is composed of lamina densa and lamina reticularis; hence, the basement membrane includes only a portion of basal lamina, and including a layer not found in basal lamina.

2. (embryology) the ventral plate of the embryonic neural tube that gives rise to somatic and visceral motor neurons.