Dura mater. Dura mater (UK /ˈdjʊərə ˈmeɪtər/ or US /ˈdʊərə ˈmætr/), or dura, is a thick membrane that is the outermost of the three layers of the meninges that surround the brain and spinal cord. It is derived from mesoderm. The other two meningeal layers are the arachnoid mater and the pia mater.