Microscopic Morphology and Ultrastructure of Human Peripheral Nerves

Microanatomical Nerve Architecture of 6 Mammalian Species

“…For example, larger animal species may not be the most appropriate species to extrapolate to humans, and as has been observed in the human sciatic nerve, the specific location of focus along the length of a nerve may also differ. 12 The microanatomical features of the endoneurium, 13,14 perineurium, 15,16 and epineurium, 17 as well as axon types, are comparable to those of the sciatic nerve in humans. Nevertheless, the characteristics of topograms, number, size, radius, and circumference of fascicles; organization of groups and subgroups of fascicles within a nerve; and relation of neural tissue (axon type, axonal area and endoneurium) to nonneural tissue (mainly connective and adipose tissue) are different among peripheral nerves in the species studied.…”

Another (Internal) Epineurium: Beyond the Anatomical Barriers of Nerves

“…The endoneurium and epineurium are formed of collagen fibers through which local anesthetic agents can diffuse according to Fick's Principle of Diffusion (Reina et al, ; Reina et al, , ; Reina and Sala‐Blanch, ; Reina et al, ). The perineurium is formed of cells that are tightly bound together and is semipermeable (Reina et al, ; Reina et al, , ). This is the barrier that governs, for example, the passage of drugs such as local anesthetics to axons, thus delaying their effects (e.g., the anesthetic effect).…”

“…However, the terminology remains confusing (Franco, ) (Table ). Some name the outer layer of a nerve, which is formed by collagen fibers, the epineurium, whereas others have called the tissue outside the fascicles the epineurium, while also including the border of the nerve and the interfascicular tissue (Gambe and Eames, ; Stolinski, ; Reina et al, , , , ; Sala‐Blanch et al, ). The layers that group several fascicles together inside a nerve are not fully understood.…”

The utility of three‐dimensional optical projection tomography in nerve injection injury imaging

“…A fascicular group is a pack of nerve fascicles that are connected by interconnecting fascicles and that, by building up an intraneural plexus, exhibit the same pattern at distinct anatomical parts of the nerves . These are difficult to demonstrate with 2D histological sections, nor can axons and myelin be analysed by OPT, which makes histological analysis and OPT complementary.…”