Endoneurium
Encyclopedia
The endoneurium, also referred to as an endoneurial channel, sheath or tube, is a layer of delicate connective tissue
made up of endoneurial cells that encloses the myelin sheath of a spinal cord
nerve fiber
. These are bundled up into groups called nerve fascicle
s, which have a protective sheath called a perineurium
. Several fascicles may be in turn bundled together with a blood
supply and fatty tissue within yet another sheath, the epineurium. The endoneurium contains a low protein
liquid known as endoneurial fluid that is the peripheral nervous system
equivalent to cerebro-spinal fluid in the central nervous system
. Peripheral nerve injuries can be identified by checking for increased amounts of endoneurial fluid using magnetic resonance neurography
.
It is continuous with septa which pass inward from the innermost layer of the perineurium, and shows a ground substance in which are imbedded fine bundles of fibrous connective tissue, primarily collagen
, running for the most part longitudinally. It serves to support capillary
blood vessel
s, arranged so as to form a network with elongated meshes. It is found in other places too, such as surrounding the Schwann cell
s on the peripheral side of the transitional zone on the auditory nerve.
Connective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
made up of endoneurial cells that encloses the myelin sheath of a spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
nerve fiber
Nerve fiber
A nerve fiber is a threadlike extension of a nerve cell and consists of an axon and myelin sheath in the nervous system. There are nerve fibers in the central nervous system and peripheral nervous system. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system , myelin...
. These are bundled up into groups called nerve fascicle
Nerve fascicle
A small bundle of nerve fibers, enclosed by the perineurium, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or nerve fascicles, which are bound together in a common membranous...
s, which have a protective sheath called a perineurium
Perineurium
In the peripheral nervous system, 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...
. Several fascicles may be in turn bundled together with a blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
supply and fatty tissue within yet another sheath, the epineurium. The endoneurium contains a low protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
liquid known as endoneurial fluid that is the peripheral nervous system
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
equivalent to cerebro-spinal fluid in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Peripheral nerve injuries can be identified by checking for increased amounts of endoneurial fluid using magnetic resonance neurography
Magnetic resonance neurography
Magnetic resonance neurography 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 nerve from the resonance signal that arises from in the...
.
It is continuous with septa which pass inward from the innermost layer of the perineurium, and shows a ground substance in which are imbedded fine bundles of fibrous connective tissue, primarily collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
, running for the most part longitudinally. It serves to support capillary
Capillary
Capillaries are the smallest of a body's blood vessels and are parts of the microcirculation. They are only 1 cell thick. These microvessels, measuring 5-10 μm in diameter, connect arterioles and venules, and enable the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste...
blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s, arranged so as to form a network with elongated meshes. It is found in other places too, such as surrounding the Schwann cell
Schwann cell
Schwann cells or neurolemmocytes are the principal glia of the peripheral nervous system . Glial cells function to support neurons and in the PNS, also include satellite cells, olfactory ensheathing cells, enteric glia and glia that reside at sensory nerve endings, such as the Pacinian corpuscle...
s on the peripheral side of the transitional zone on the auditory nerve.
See also
- Connective tissue in the peripheral nervous systemConnective tissue in the peripheral nervous systemA peripheral nerve contains two types of tissue: nerve fibers, and connective tissue. Dendrites and axons with schwann cells and myelin sheath are surrounded by connective tissue. A nerve fiber in the peripheral nervous system consists of an axon or long dendrite, myelin sheath and their schwann...
- EpineuriumEpineuriumThe epineurium is the outermost layer of connective tissue surrounding a peripheral nerve. It is made of dense irregular connective tissue and usually contains multiple nerve fascicles as well as blood vessels which supply the nerve...
- Nerve fascicleNerve fascicleA small bundle of nerve fibers, enclosed by the perineurium, is called a funiculus; if the nerve is of small size, it may consist only of a single funiculus; but if large, the funiculi are collected together into larger bundles or nerve fascicles, which are bound together in a common membranous...
- Nerve fiberNerve fiberA nerve fiber is a threadlike extension of a nerve cell and consists of an axon and myelin sheath in the nervous system. There are nerve fibers in the central nervous system and peripheral nervous system. A nerve fiber may be myelinated and/or unmyelinated. In the central nervous system , myelin...
- PerineuriumPerineuriumIn the peripheral nervous system, 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...
External links
- "Ultrastructure of the Cell: myelinated axon and Schwann cell" - "Ultrastructure of the Cell: arteriole and peripheral nerve"- Histology at University of California, Los AngelesUniversity of California, Los AngelesThe University of California, Los Angeles is a public research university located in the Westwood neighborhood of Los Angeles, California, USA. It was founded in 1919 as the "Southern Branch" of the University of California and is the second oldest of the ten campuses...
- Diagram at Howard UniversityHoward UniversityHoward University is a federally chartered, non-profit, private, coeducational, nonsectarian, historically black university located in Washington, D.C., United States...
