Ramus communicans (: 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 A spinal nerve is a mixed nerve, which carries Motor neuron, motor, Sensory neuron, sensory, and Autonomic nervous system, autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each s ...

and the

sympathetic trunk The sympathetic trunk (sympathetic chain, gangliated cord) is a paired bundle of nerve fibers that run from the base of the skull to the coccyx. It is a major component of the sympathetic nervous system. Structure The sympathetic trunk lies just ...

. More specifically, it usually refers to one of the following : * Gray ramus communicans * White ramus communicans The grey and white rami communicantes are responsible for conveying autonomic signals, specifically for the

sympathetic nervous system The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...

. Their difference in colouration 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.

White ramus communicans

The white rami communicantes exist only at the levels of the spinal cord where the intermediolateral cell column is present (T1-L2) and are responsible for carrying preganglionic nerve fibres from the spinal cord to the paravertebral ganglia. Both ramus within the

cross each other, being the white further away from the intervertebral foramen when exiting the spinal nerve to enter the ganglia. (More so, some fibres from the white ramus may migrate to other ganglia without even synapsis on its level)

References

{{DEFAULTSORT:Ramus Communicans Nerves of the torso