The sacral plexus is a nerve plexus that provides motor and sensory nerves for the posterior thigh, most of the lower leg, the entire foot, and part of the pelvis. It is part of the lumbosacral plexus and emerges from the sacral vertebrae (S2–S4).
The largest and longest nerve of the human body, the sciatic nerve, is the main branch and gives rami to the motor innervation of the muscles of the foot, the leg, and the thigh.
The sacral plexus
The nerves of the sacral plexus are shown.
The sacral plexus is formed by:
- The lumbosacral trunk.
- The anterior division of the first sacral nerve.
- Portions of the anterior divisions of the second and third sacral nerves.
The nerves forming the sacral plexus converge toward the lower part of the greater sciatic foramen and unite to form a flattened band from the anterior and posterior surfaces, from which several branches arise.
The band itself is continued as the sciatic nerve, which splits on the back of the thigh into the tibial nerve and the common fibular nerve. These two nerves sometimes arise separately from the plexus and, in all cases, their independence can be shown by dissection.
Often, the sacral plexus and the lumbar plexus are considered to be one large nerve plexus, the lumbosacral plexus. The lumbosacral trunk connects the two plexuses.
The coccygeal plexus originates from the S4, S5, and Co1 spinal nerves. It is interconnected with the lower part of the sacral plexus. The only nerve in this plexus is the anococcygeal nerve, which serves sensory innervation of the skin in the coccygeal region.
Sacral plexus diagram
Diagram of the sacral plexus showing the various anterior and posterior nerve branches that arise from each lumbar and sacral nerve.