<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>
which layer of the meninges is connected to the brain
The pia mater