abnormal basement membrane morphology abnormal basal lamina morphology any structural anomaly of the sheet of extracellular matrix characteristically situated under epithelial cells, around muscles, nerves, capillaries, and fat cells, and situated between these elements and the underlying or surrounding connective tissue MP:0004273 Note: Basal lamina and lamina reticularis (or of two basal laminae) compose the basement membrane. Thus, in strict sense, the term basement membrane is different from and should not be confused with basal lamina. MPheno.ontology