The ventral ramus (pl. rami) (Latin for branch) is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk and the limbs. They are mainly larger than the dorsal rami.
Shortly after a spinal nerve exits the intervertebral foramen, it branches into the dorsal ramus, ventral ramus, and ramus communicans. Each of these three structures carries both sensory and motor information. Because each spinal nerve carries both sensory and motor information, spinal nerves are referred to as “mixed nerves.”
In the thoracic region they remain distinct from each other and each innervates a narrowstrip of muscle and skin along the sides, chest, ribs, and abdominal wall. These rami are called theintercostal nerves. In regions other than the thoracic, ventral rami converge with each other to form networks of nervescalled nerve plexuses. Within each plexus, fibers from the various ventral rami branch andbecome redistributed so that each nerve exiting the plexus has fibers from several different spinalnerves. One advantage to having plexuses is that damage to a single spinal nerve will not completelyparalyze a limb.
There are four main plexuses formed by the ventral rami:the cervical plexus contains ventral rami from spinal nerves C1-C4. Branches of thecervical plexus, which include the phrenic nerve, innervate muscles of the neck, the diaphragm, and theskin of the neck and upper chest.The brachial plexus contains ventral rami from spinal nerves C5-T1. This plexus innervatesthe pectoral girdle and upper limb.The lumbar plexus contains ventral rami from spinal nerves L1-L4. The sacral plexus contains ventralrami from spinal nerves L4-S4. The lumbar and sacral plexuses innervate the pelvic girdle and lowerlimbs.
Ventral rami, including the sinuvertebral nerve branches, also supply structures anterior to the facet joint, including the vertebral bodies, the discs and their ligaments, and joins other spinal nerves to form the lumbo-sacral plexus.