The standard sight is that the mind is bordered by 3 layers, the dura, arachnoid, and also pia mater. Møllgård et al. located a 4th meningeal layer called the subarachnoid lymphatic-like membrane layer (SLYM). SLYM is immunophenotypically distinctive from the various other meningeal layers in the human and also computer mouse mind and also stands for a limited obstacle for solutes of greater than 3 kilodaltons, efficiently partitioning the subarachnoid area right into 2 various areas. SLYM is the host for a huge populace of myeloid cells, the variety of which raises in reaction to swelling and also aging, so this layer stands for an inherent immune particular niche preferably placed to surveil the cerebrospinal liquid.