Trunk nerves (intercostal, sympathetic, vagus nerve)
Anterior (ventral) spinal roots
Radices anteriores (ventrales) nervorum spinalium
- Origin
- Emerge from the anterior/ventral gray horn of the spinal cord as rootlets (fila radicularia)
- Insertion
- Pass through the intervertebral foramen to join the posterior root distal to the dorsal root ganglion, forming the mixed spinal nerve
- Function
- Carries purely efferent motor axons (alpha and gamma motor neurons) to skeletal muscles, as well as sympathetic preganglionic fibers (T1-L2)
- Innervation
- Somatomotor and preganglionic autonomic efferent
- Movement & chain
- Motor action potential conduction driving voluntary and reflex muscle contraction
- Palpation
- Assessed by myotomal muscle strength testing (MRC grade 0-5) and deep tendon reflexes
- Clinical
- Motor radiculopathy (muscle weakness and flaccid paresis from herniated intervertebral disc), Amyotrophic Lateral Sclerosis (ALS: anterior horn cell loss causing progressive weakness and fasciculations), Poliomyelitis.
- Segmental innervation
- Spinal myotomes C1-S5
- In clinical practice
- Systematic myotome muscle charting (L4 knee extension, L5 big toe dorsiflexion, S1 plantarflexion), fall prevention in lower limb motor weakness
- Region in the model
- Trunk nerves (intercostal, sympathetic, vagus nerve)