( 4 ) an approximately 200-a extracellular gap occurs around the axon and between the innermost sheath laminae , but it is separated from surrounding extracellular spaces by gap closure between the outer sheath laminae , as the membranes of adjacent laminae adhere to form external compound membranes ( ecm 's ) .
C0015352
extracellular spaces
C0015350
ecm 's