nerveplexus

A nerve plexus is a network of intersecting nerves formed by the ventral rami of adjacent spinal nerves that reorganize into peripheral nerves. This arrangement allows a single spinal level to contribute to multiple nerves and provides redundancy in motor and sensory innervation of the limbs and trunk.

In humans, the major nerve plexuses are the cervical, brachial, lumbar, and sacral, with a coccygeal plexus sometimes noted. The cervical plexus comprises the ventral rami of C1 to C4 and supplies parts of the neck and the diaphragm via the phrenic nerve and several cutaneous and muscular branches. The brachial plexus, derived from C5 to T1, yields the major nerves of the upper limb, including the musculocutaneous, axillary, radial, median, and ulnar nerves. The lumbar plexus, from L1 to L4, services the lower limb’s anterior compartment, giving rise to the femoral and obturator nerves among others. The sacral plexus, formed by L4 to S4, supplies most of the lower limb, with the sciatic and pudendal nerves being prominent branches. A coccygeal plexus, when present, involves contributions from S4 to Co1 and innervates small areas around the coccyx.

Structure and development: plexuses organize by channeling the nerve fibers from spinal nerves into regional networks, which then distribute into named peripheral nerves. This arrangement supports coordinated motor control and sensory coverage across broad areas, while allowing overlap between adjacent dermatomes and redundancy in function.

Clinical relevance: injuries or compressions of a plexus can affect several distal nerves, producing sensory loss and motor weakness in a region rather than a single nerve distribution. Nerve blocks or regional anesthesia often target a plexus (for example, the brachial plexus) to anesthetize specific body regions.