Small nerves might comprise a single funiculus, but in case of large nerves, the funiculi join to form large bundles of nerve fibers called fasciculi. These are kept together by membranous sheaths or layers of connective tissue called endoneurium, perineurium, and epineurium. The epineurium is a sense layer of connective tissue that envelops the entire nerve trunk. It surrounds the fascicles and the blood vessels that supply the nerve.