Sacral nerve plexus


Just inferior to the lumbar plexus lies the sacral plexus. The anterior rami of spinal nerves lumbar 4 and 5 as well as sacral 1 through 4 create the sacral plexus. The pelvis, the lower back, the perineum, the sections of the foot (dorsal and plantar) and sections of the thigh and leg ( posterior surface) all are innervated by the nerves that branch off the sacral plexus.


The sacral plexus is similar to the lumbar plexus by design. It contains roots, the anterior division and the posterior division. The lumbar plexus and the sacral plexus are sometimes grouped together into one plexus due to their similar design and their proximity to each other. When called as one plexus, it is referred to as the lumbosacral plexus, receiving its name because the nerves pass through the lumbosacral trunk.

The sacral plexus reveals the largest nerve in the human body, the sciatic nerve. This nerve traverses from the pelvis, through a notched named for the nerve, and then runs down along the posterior aspect of the thigh.

The sciatic nerve is technically two nerves which come together as one and are protected in a sheath. The tibial nerve and the common fibula nerve comprise the sciatic nerve.


Sacral Plexus
Image: Sacral Plexus

The anterior division of the sacral plexus yields the tibial nerve. It rises up through the posterior segments of the thigh and the leg. From there, it branches off to create the foot’s medial and lateral plantar nerve. The tibial nerve innervates the calf of the leg, and the plantar portion of the foot, coetaneous speaking. The posterior thigh muscles, leg muscles, and numerous intrinsic muscles of the foot receive motor innervation.

The common fibular nerve is also known as the peroneal nerve. The posterior division of the sacral plexus yields this nerve. This nerve runs through the posterior section of the thigh and then branches off into the upper leg while burying deep into the superficial fibular nerves. The common fibular nerve innervates the skin and the branches innervate the anterior and lateral leg along with the muscles of the foot.
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