part of part of has part has part has_part located in located in bounding layer of bounding layer of collagen trimer perineurium A layer of thin, concentrically arranged cells with interspersed collagen that lies within the epineurium. The perineurium is a component of the blood–nerve barrier and is essential for protecting axons and their associated Schwann cells from ionic flux, toxins and infection. NCIT:C33302 Wikipedia:Perineurium NCIT:C41407 FMA:52585 SCTID:362299001 BTO:0003153 UBERON:0000121 NLXANAT:090205 epineurium nervous system nerve fasciculus blood nerve barrier dense irregular connective tissue