<P> The pia mater (Latin: tender mother) is a very delicate membrane . It is the meningeal envelope that firmly adheres to the surface of the brain and spinal cord, following all of the brain's contours (the gyri and sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid . The pia mater is pierced by blood vessels to the brain and spinal cord, and its capillaries nourish the brain . </P> <P> The arachnoid and pia mater together are sometimes called the leptomeninges, literally "thin meninges" (Greek: λεπτός leptos - thin). Acute meningococcal meningitis can lead to an exudate within the leptomeninges along the surface of the brain . Because the arachnoid is connected to the pia by cob - web like strands, it is structurally continuous with the pia, hence the name pia - arachnoid or leptomeninges . They are responsible for the production of beta - trace protein (prostaglandin D synthase) a major cerebrospinal fluid protein . </P> <P> The subarachnoid space is the space that normally exists between the arachnoid and the pia mater, which is filled with cerebrospinal fluid, and continues down the spinal cord . Spaces are formed from openings at different points along the subarachnoid space and these are the subarachnoid cisterns which are filled with cerebrospinal fluid . </P> <P> The dura mater is attached to the skull, whereas in the spinal cord, the dura mater is separated from the vertebrae by a space called the epidural space, which contains fat and blood vessels . The arachnoid is attached to the dura mater, while the pia mater is attached to the central nervous system tissue . When the dura mater and the arachnoid separate through injury or illness, the space between them is the subdural space . There is a subpial space underneath the pia mater that separates it from the glia limitans . </P>

Where is the meninges located in the brain