Anterior Root of First Sacral Nerve (Right)

Origin

The anterior root of the first sacral nerve originates as a series of rootlets that emerge from the ventrolateral surface of the spinal cord. These quickly merge to form the anterior root.

Course

The anterior root runs inferiorly. At lumbar and sacral levels, the anterior root descends through the vertebral column until it reaches the first sacral foramen. Just before it enters this foramen, the anterior and posterior roots merge to form the spinal nerve.

Branches

There are no named branches; however, fibers do contribute to the sacral plexus and, specifically, the superior gluteal, inferior gluteal, and sciatic nerves.

Supplied Structures

The anterior root of the first sacral nerve supplies the multifidus muscle via the posterior ramus. It also contributes to the sacral plexus, and the following nerves and targets.

—The superior gluteal nerve arises from the fourth and fifth lumbar nerves as well as the first sacral nerve. It innervates the gluteus medius, gluteus minimus, and tensor fasciae latae.

—The inferior gluteal nerve arises from the fifth lumbar nerve and the first and second sacral nerves. It innervates the gluteus maximus muscle.

—The sciatic nerve is the longest nerve in the body. It gives rise to the common fibular, tibial, and sural nerves. It arises from the fourth and fifth lumbar nerves as well as the first, second, and third sacral nerves. The sciatic nerve innervates all the muscles of the posterior thigh, anterior and posterior leg, and foot.

Muscles largely innervated by the anterior root of the first sacral nerve include the gastrocnemius, soleus, peroneus longus, peroneus brevis, and gluteus maximus muscles.