Gray ramus communicans

Gray ramus communicans
Latin r. communicans griseus
TA A14.3.01.006
FMA 5876

Anatomical terminology

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 nervous system and are composed of largely unmyelinated neurons. This is in contrast to the white rami communicantes, in which heavily myelinated neurons give the rami their white appearance.


Preganglionic sympathetic fibres from the intermediolateral nucleus in the lateral grey column of the spinal cord are carried in the white ramus communicans to the paravertebral ganglia of the sympathetic trunk. Once the preganglionic nerve has traversed a white ramus communicans, it can do one of three things.

Ganglionic influence can be specifically targeted to end organs as well as becoming part of a summating systemic response. If the response is the whole body response, as in sympathetic fight or flight, the signals are distributed to other spinal nerves by way of gray rami communicantes which serve as conduits between the spinal nerves.

Specific Functions in the ANS

Some cervical ganglia and thoracic ganglia send gray rami communicantes directly to the heart. [1]
Thoracic ganglia send grey rami communicantes to their adjacent body wall. They supply blood vessels, sweat glands, and arrectores pilorum muscles.
Lumbar ganglia have grey rami communicantes that rejoin the appropriate spinal nerves to supply the abdominal wall and lower limbs.
The pelvic ganglia form grey rami communicantes whose lateral (postganglionic) branches supply the pelvic wall and lower limb.


This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

  1. F. Netter, Autonomic Nervous System: Schema, Back and Spinal Cord, Plate 153

Wilson-Pauwels, Linda; Stewart, Patricia A.; Akesson, Elizabeth J. (January 1997). Autonomic Nerves. Canada: B. C. Decker, Inc. pp. 71–104. ISBN 978-1-55009-030-7. 

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