can you tell me something about the first one mentioned above?
It is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord.
Pia mater
Pia mater ( or ), often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. 
which layer of meninges is affected in meningitis The three membranes - pia mater, arachnoid mater and dura mater
wiki:1821319
Pia mater [SEP] Introduction
Pia mater ( or ), often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. "Pia mater" is medieval Latin meaning "tender mother". The other two meningeal membranes are the dura mater and the arachnoid mater. Both the pia and arachnoid mater are derivatives of the neural crest while the dura is derived from embryonic mesoderm. The pia mater is a thin fibrous tissue that is permeable to water and small solutes. The pia mater allows blood vessels to pass through and nourish the brain. The perivascular space between blood vessels and pia mater is proposed to be part of a pseudolymphatic system for the brain (glymphatic system).