Gray ramus communicans

Gray ramus communicans
Scheme showing structure of a typical spinal nerve. 1. Somatic efferent. 2. Somatic afferent. 3,4,5. Sympathetic efferent. 6,7. Sympathetic afferent.
Diagram of the course and branches of a typical intercostal nerve. (Rami communicantes labeled at center.)
Latin	ramus communicans griseus nervi spinalis
Gray's	subject #208 920

Each spinal nerve receives a branch, gray ramus communicans, from the adjacent ganglion of the sympathetic trunk.

They contain unmyelinated postganglionic sympathetic fibers.

Function (overview)

After signals are carried from the spinal cord to the ganglion through the ventral ramus, they synapse in the ganglion, and then post-ganglionic fibres carry them to the organs that they innervate. But 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 which serve as bridges between the spinal nerves.

Specific Functions in the ANS

All Thoracic ganglia send grey rami communicantes to their adjacent body wall. They supply blood vessels, sweat glands, and arrectores pilorum muscles.

All 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.

References

Wilson-Pauwels, Linda; Stewart, Patricia A.; Akesson, Elizabeth J. (January 1997). Autonomic Nerves. Canada: B. C. Decker, Inc.. pp. 71-104. ISBN 978-1550090307. 

Additional Images

• 

  Deep and superficial dissection of the lumbar plexus.

• 

  Thoracic portion of the sympathetic trunk.

See also

• White ramus communicans

External links

• gray+rami+communicantes at eMedicine Dictionary
• Atlas of anatomy at UMich n3a6p1 - "Autonomic Connections of the Spinal Cord"
• Overview and diagram

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.