Further to our exploration of the cranial and spinal meninges, I wanted to expand today on the remarkable Pia Mater – the “tender Mother” in contrast to the “tough Mother” that is the Dura Mater. Both the Pia and Arachnoid Mater derive from of the neural crest while the Dura is derived from embryonic mesoderm.
The Pia Mater is that most delicate innermost layer of the meninges, spanning both the spinal cord and the fissures of the cerebral cortex. Composed of fibrous connective tissue covered by a sheet of flat cells, it is impermeable to fluid on its outer surface.
The Pia Mater allows blood vessels to pass through so nourishing the brain itself. The perivascular space between blood vessels and pia mater is proposed to be part of a pseudolymphatic system for the brain (glymphatic system) (Hladky et al. 2014: Jessen et al. 2015).
A subarachnoid space exists between the arachnoid layer and the pia, into which the choroid plexus releases and maintains the cerebrospinal fluid (CSF). The subarachnoid space contains trabeculae, or fibrous filaments, that connect and stabilise the two layers, allowing for the appropriate balance of proteins, electrolytes, ions, and glucose contained within the CSF.
Ah, fascia in all its manifestations never ceases to amaze!
Photo Credit to Haneen Al.Maghrabi