The endoneurium (also called endoneurial channel, endoneurial sheath, endoneurial tube, or Henle's sheath) is a layer of delicate
connective tissue
Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...
around the
myelin sheath of each myelinated
nerve fiber
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...
in the
peripheral nervous system.
Its component cells are called endoneurial cells.
The endoneuria with their enclosed nerve fibers are bundled into groups called
nerve fascicle
A nerve fascicle, is a bundle of nerve fibers belonging to a nerve in the peripheral nervous system. A nerve fascicle is also called a fasciculus. A nerve fascicle is enclosed by perineurium, a layer of fascial connective tissue. Each enclosed ...
s,
each fascicle within its own protective sheath called a
perineurium.
In sufficiently large nerves multiple fascicles, each with its
blood supply and fatty tissue, may be bundled within yet another sheath, the
epineurium
The epineurium is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve. Smaller branches of these blood vessels p ...
.
The endoneurium contains a liquid known as
endoneurial fluid, which contains little
protein. In the
peripheral nervous system the endoneurial fluid is notionally equivalent to
cerebrospinal fluid in the
central nervous system. Peripheral nerve injuries commonly release increased amounts of endoneurial fluid into surrounding tissues; these can be detected by
magnetic resonance neurography
Magnetic resonance neurography (MRN) is the direct imaging of nerves in the body by optimizing selectivity for unique MRI water properties of nerves. It is a modification of magnetic resonance imaging. This technique yields a detailed image of a ne ...
, thereby assisting in locating injuries to peripheral nerves.
The endoneurium runs longitudinally along the nerve fiber, but with discontinuities where
septa pass inward from the innermost layer of the perineurium. It contains fine bundles of
fibrous connective tissue, primarily
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...
, embedded in a matrix of
ground substance. This structure serves to support
capillary blood vessels, arranged so as to form a network of elongated meshes. Similar structures occur around some nervous components elsewhere in the body, for example around the
Schwann cells on the peripheral side of the transitional zone on the
auditory nerve
The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information ...
.
See also
*
Connective tissue in the peripheral nervous system
Nervous tissue, also called neural tissue, is the main tissue (biology), tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) com ...
*
Epineurium
The epineurium is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. It usually surrounds multiple nerve fascicles as well as blood vessels which supply the nerve. Smaller branches of these blood vessels p ...
*
Nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
*
Nerve fascicle
A nerve fascicle, is a bundle of nerve fibers belonging to a nerve in the peripheral nervous system. A nerve fascicle is also called a fasciculus. A nerve fascicle is enclosed by perineurium, a layer of fascial connective tissue. Each enclosed ...
*
Nerve fiber
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...
*
Nervous system
*
Perineurium
References
External links
* - "Ultrastructure of the Cell: myelinated axon and Schwann cell"
* - "Ultrastructure of the Cell: arteriole and peripheral nerve"
*
Histologyat
University of California, Los Angeles
Diagramat
Howard University
{{Authority control
Neurohistology