The document discusses the microanatomy of peripheral nerves. It describes the structure of peripheral nerve fibers including the epineurium, perineurium, fascicles, axons, and endoneurium. It explains the relevance of this microstructure in nerve repair and regeneration. Finally, it outlines the topography of major peripheral nerves of the upper limb including the brachial plexus, median nerve, radial nerve, and ulnar nerve.

1. {
Microanatomy of the
nerve
Aymeric Lim, National University Hospital.

2.  At the end of the lecture the participant will be able
to:
1. Describe the structure of the peripheral nerve fiber
and name its major components
2. Identify the microstructure of the peripheral nerve
and its relevance in nerve repair and regeneration
3. Describe the topography of major peripheral nerves
of the upper limb

3. 1. Describe the structure of the peripheral nerve fiber and name its major
components

4. 1. Internal epineurium
2. External epineurium
3. Fascicle
4. Perineurium
5. Axons
6. Endoneurium

5. epi-
 a prefix occurring in
loanwords from Greek,
where it meant “upon,”
“on,” “over,” “near,” “at,”
“before,” “after” (
epicedium; epidermis;
epigene; epitome

6. The epineurium
 Nerve fascicles are embedded in a
connective tissue matrix called the
epineurium, which provides a
supportive and protective
framework for the fascicles.
 Solutions diffuse widely through
this layer.
 Adipose tissue may be present in
this area.
 Composed of nerves, lymphatics
and the largest nutrient vessels.
 Cross-sectional area of a nerve
trunk composed of epineurium
varies from 30 to 75%.

7. Protective effects of the
epineurium

8.  a prefix meaning “about” or “around” ( perimeter,
periscope ), “enclosing” or “surrounding” (
pericardium ), and “near” ( perigee, perihelion ),
appearing in loanwords from Greek ( peripeteia );
on this model, used in the formation of compound
words ( perimorph ).
peri-

9. The perineurium
 Individual nerve fibers collect into
fascicles, which are surrounded by
a connective layer called the
perineurium.
 Thin but dense
 This provides the bulk of the
mechanical strength.
 The elasticity and integrity of a
nerve in tension are maintained as
long as this layer remains intact.
 Maintains an intrafascicular
pressure.

10. Mushrooming

11. Nerve cuts

15. Microscopically perfect
repair

16. Endo-
 a combining form meaning
“within,” used in the
formation of compound
words: endocardial.
 Also, especially before a
vowel , end-.

Origin:
< Greek, combining form of
éndon within; cognate with
Old Irish ind-, OL endo- in,
on

17. The endoneurium
 Within the fascicles, the individual
nerve fibers are separated by a
connective tissue framework
called the endoneurium.
 Condenstations form fine septa
that divide the nerve fibres into
small groupings.
 Only vessels found here are
capillaries.
 Has extensibility and elasticity.
Allowing regeneration duriing
regeneration.

19. 2. Identify the microstructure of the peripheral nerve and its relevance in
nerve repair and regeneration

20. The internal plexus:
Fascicular anatomy

21. Biologic Laws of Nerve Fiber
Distribution
 The course of the nerve
fibres is fixed by natural
and logical rules of
distribution.
 This is according to the
locations of the muscles
at different levels of the
limb.
 Zancolli,

22. Law 1
 Fasciculi of nerve
fibres with different
functions intermingle
to produce complex
plexuses.
 In the proximal zone
of nerve trunks.
 Max intermingling of
nerve fibres from
different spinal cord
segments.
 Also exists distal to
the emergence of
the collateral
branches.

23. Law 2
 Long and short nerve fibres
regroup to form the collateral
branches of the nerve trunk.
 Short to periphery.
 Long central.
 Quadrantic arrangements.

24. Law 3
 Nerve fibres regroup according
to basic functions of the upper
limb.
 Brachial plexus: anterior and
posterior.
 Nerves: sensory and motor.

25. Law 4
 Nerve fibres regroup within
nerve branches.

26.  Fascicular arrangement of
the peripheral nerves by
zones

28. 3. Describe the topography of major peripheral nerves of the upper limb

29. Fascicular topography

31. The brachial plexus

32. Orderly sequence of dermatomal
distribution

33. Pathways of the brachial plexus

34. Median nerve
 Nerve of the forearm flexors
and the thenar eminence

36. Radial nerve
 Nerve of the extensors of the
arm and the forearm

38. Ulnar nerve
 Nerve of the hand

40.  At the end of the lecture the participant will be able
to:
1. Describe the structure of the peripheral nerve fiber
and name its major components
2. Identify the microstructure of the peripheral nerve
and its relevance in nerve repair and regeneration
3. Describe the topography of major peripheral nerves
of the upper limb

42. The general organization of fascicles
 (1) Fascicles repeatedly divide and
unite to form fascicular plexuses
and, therefore, are not arranged
as parallel uninterrupted strands
along the entire length of a nerve.
 (2) No fascicle runs an unaltered
course along the length of a
nerve; however, at a given level,
some fascicles may not participate
in plexus formation.
 (3) The precise form of a plexus
varies from nerve to nerve, level
to level, side to side, and
individual to individual.

43. The general organization of fascicles
 (4) The size and number of fascicles are inversely
related at any given level.
 (5) The diameters of most fascicles range from 40 µm
to 2mm.

44. The general organization of fascicles
 (6) Fascicles are smaller and
more numerous where a
nerve crosses a joint,
presumably to allow for
nerve deformation without
damage.
 (7) For a given fascicular
area, nerve tensile strength
increases with the number
of fascicles.

46. Motor organization
of the brachial
plexus