Sacral plexus

The sciatic nerve is derived from the ventral rami of spinal nerves L4-S3. The ventral divisions of these rami form the tibial component of the sciatic nerve, which lies on the medial aspect of the sciatic nerve. The dorsal divisions form the peroneal component, which lies on the lateral aspect of the nerve. These two components maintain this orientation as they course together as the common sciatic nerve, until they split into individual nerves just proximal to the popliteal crease.