<prompt> Blood nerve barrier is formed by:PerineuriumSchwann cellsEpineuriumEndoneurium  <response>: Ref: Histology a Text and Atlas, 6th edition, Michael H. Ross, Page 376Explanation:Together with endothelial cells of blood vessels within the fascicle, perineurial cells constitute part of the blood-nerve barrier, an important andselective diffusion barrier against entry of potentially infectious and toxic substances that may alter normal function of the nerve. Ref: Netters Essential Histology by Ovalle WK, 2nd edition. Page 130Tight junctions, providing the basis for the blood- ner!e barrier, are present between the cells located within the same layer of the perineurium. Ref: Histology by Ross MH, 5th edition. Page 342The perineurium has the character of an epithelium, called perineurial epithelium, and functionally contributes to the formation of a blood- nerve barrier blood-brain barrierRef: Functional Ultrastructure: Atlas of Tissue Biology and Pathology By Margit Pavelka, Page 324BLOOD NERVE BARRIERFormed by Perineurium of Peripheral Nerves and the endothelium of endoneurial Capillaries.The perineurium acts as a diffusion barrier.but ion permeability is higher than at the blood- brain barrier.ALSO NOTEBlood Brain Barrier BBBFormed by:o Tight junctions of endothelial cellso Foot process of the astrocytes around the capillaries.Filters only Lipid soluble substances.Areas outside BBB--Collectively known as Circumven-tricular organs: Mnemonic-M. SOAPo Median eminenceo Sub fornical organo Organum vasculosumo Area postrcmao Posterior pituitary. 