Ramus communicans (plural rami communicantes) is the Latin term used for a nerve which connects two other nerves, and can be translated as "communicating branch".
Structure
When used without further definition, it almost always refers to a communicating branch between a
spinal nerve and the
sympathetic trunk
The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system.
Structure
The sympathetic trunk lies j ...
. More specifically, it usually refers to one of the following :
*
Gray ramus communicans
Each spinal nerve receives a branch called a gray ramus communicans (plural rami communicantes) from the adjacent paravertebral ganglion of the sympathetic trunk. The gray rami communicantes contain postganglionic nerve fibers of the sympathetic ne ...
*
White ramus communicans
The white ramus communicans (plural: rami communicantes) from Latin ramus (branch) and communicans (communicating) is the preganglionic sympathetic outflow nerve tract from the spinal cord.
Each of the thoracic, and the first and second lumbar ne ...
The grey and white rami communicantes are responsible for conveying
autonomic signals, specifically for the
sympathetic nervous system. Their difference in coloration is caused by differences in myelination of the nerve fibres contained within, i.e. there are more myelinated than unmyelinated fibres in the white rami communicantes while the converse is true for the grey rami communicantes.
Gray ramus communicans
The grey rami communicantes exist at every level of the spinal cord and are responsible for carrying
postganglionic nerve fibres from the paravertebral ganglia to their destination, and for carrying those preganglionic nerve fibres which enter the paravertebral ganglia but do not synapse.
[Blumefield]
White ramus communicans
The white rami communicantes exist only at the levels of the spinal cord where the
intermediolateral cell column
The intermediolateral nucleus (IML) is a region of grey matter found in one of the three grey columns of the spinal cord, the lateral grey column. This is Rexed lamina VII.
The intermediolateral cell column exists at vertebral levels T1 – L ...
is present (T1-L2) and are responsible for carrying
preganglionic nerve fibres from the spinal cord to the paravertebral ganglia.
Both ramus within the
spinal nerve cross each other, being the white farther away from the intervertebral foramen when exiting the spinal nerve to enter the ganglia. (More so, some fibers from the white ramus may migrate to other ganglia without even synapsis on its level)
References
{{DEFAULTSORT:Ramus Communicans
Nerves of the torso