Dictionary Definition
perineurium n : connective tissue that covers a
bundle of nerve fibers
Extensive Definition
In the spinal cord,
nerve fibers are each wrapped in a protective sheath known as the
endoneurium. These
are bundled together into groups known as fascicles, each surrounded by
a protective sheath known as the perineurium. Several fascicles may
be in turn bundled together with a blood supply and fatty tissue
within yet another sheath, the epineurium. This grouping
structure is analogous to the muscular organization system of
epimysium, perimysium and endomysium.
The perineurium is composed of connective
tissue, which has a distinctly lamellar arrangement consisting
of roughly 7-8 concentric layers. The perineurium is cellular, and
is composed of perineurial cells, which are epithelioid myofibroblasts.
Perineurial cells are sometimes referred to as myoepithelioid due to
their epithelioid
and myofibroblastoid
properties including tight
junctions, gap
junctions, external
laminae and contractility.
The perineurium, is a smooth, transparent tubular
membrane which may be easily separated from the fibers it encloses.
In contrast, the epineurium is a tough and
mechanically resistant tissue which is not easily penetrated by a
needle.
External links
- - "Peripheral nerve"
- - "PNS, nerve (LM, Low)"
- Diagram at Howard
- Histology at ucla.edu
perineurium in Chinese: 神經束膜