What is "basement membrane"

Basement \Base"ment\ (b[=a]sment), n. [F. soubassement. Of uncertain origin. Cf. Base, a., Bastion.] (Arch.) The outer wall of the ground story of a building, or of a part of that story, when treated as a distinct substructure. (See Base, n., 3 (a) .) Hence: The rooms of a ground floor, collectively.

Basement membrane (Anat.), a delicate membrane composed of a single layer of flat cells, forming the substratum upon which, in many organs, the epithelioid cells are disposed.

n. (context anatomy histology English) A thin sheet of fibrous cells that underlies the epithelium.

The basement membrane is a thin, fibrous, extracellular matrix of tissue that separates the epithelium (skin, respiratory tract, gastrointestinal tract, etc.), mesothelium (pleural cavity, peritoneal cavity, pericardial cavity, etc.) and endothelium (blood vessels, lymph vessels, etc.) from underlying connective tissue.