The term pia mater (pia) refers to one of the supporting structures of the central nervous system (CNS). It is the delicate innermost of three membranous meninges (men) that encapsulate the brain (BRN) and the spinal cord (SPC) ( Carpenter-1983, Swanson-2015 ). The others are the arachnoid (arac) and dura mater (dura). They are found in the human, macaque, rat and mouse (Swanson-2015 ). Final 11 Dec 2025.