Corpus: Gray communicating branch

The gray communicating branch is a connecting branch between the spinal nerve and the sympathetic trunk.

The gray communicating branch contains postganglionic nerve fibres of the sympathetic nervous system, with cell bodies located in the sympathetic ganglia. These fibres use the spinal nerves as pathways to reach peripheral target organs, such as blood vessels and other structures like sweat glands and small muscles.

Due to the lack of myelination in the postganglionic axons, the gray communicating branch appears grey.

See also: white communicating branch

The gray communicating branch extend from the thoracic ganglia into the thoracic wall, where they innervate structures like blood vessels, sweat glands, and small muscles that control hair erection. Some branches from the cervical and thoracic ganglia also directly innervate the heart.

In the lumbar region, the gray communicating branches connect to the local spinal nerves to innervate the abdominal wall and lower limbs. In the pelvic region, these branches innervate the walls of the pelvis and also extend to the lower extremities.

• Richard L. Drake, Wayne Vogl, Adam W. M. Mitchell: Gray's Anatomy for Students (2007), p. 82