The sciatic nerve-begins in the lower back and runs through the buttock and down the lower limb
-It is the longest and widest single nerve in the human body
-It is comprised of nerves from the L4-L5-S1-S2-S3 level of the spine.
-leave the spinal cord beneath the fourth and fifth lumbar and the first, second and third sacral vertebrae. It then descends down the back of the thigh .
The nerve passes through the sciatic foramen just below the Piriformis muscle (rotates the thigh laterally), to the back of the extension of the hip and to the lower part of the Gluteus Maximus (muscle in the buttock, thigh extension).
-The sciatic nerve then runs vertically downward into the back of the thigh, behind the knee branching into the hamstring muscles (calf) and further downward to the feet.
The nerve gives off articular and muscular branches.
-The articular branches (rami articulares) arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.
-The muscular branches (rami musculares) are distributed to the following muscles of the lower limb: biceps femoris, semitendinosus, semimembranosus, and adductor magnus.
-The articular branches (rami articulares) arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.
-The muscular branches (rami musculares) are distributed to the following muscles of the lower limb: biceps femoris, semitendinosus, semimembranosus, and adductor magnus.
The nerve to the short head of the biceps femoris comes from the common peroneal part of the sciatic, while the other muscular branches arise from the tibial portion, as may be seen in those cases where there is a high division of the sciatic nerve.
-The muscular branch eventually gives off the tibial nerve and common fibular nerve, which innervates the muscles of the (lower) leg. The tibial nerve goes on to innervate all muscles of the foot except the extensor digitorum brevis (which is innervated by the peroneal nerve).
1. sciatic nerve (L45S123)
1. comprised of two main nerves – common peroneal (L45S12) and tibial (L45S123)
1. peroneal most commonly injured
1. peroneal has two divisions: superficial and deep; if the superficial branch is involved then there will be hypalgesia on the anterolateral aspect of the foot
2. if the deep division is affected there will be weakness in dorsiflexion and inversion of the foot with a sensory loss between the web area of the first two toes
2. tibial nerve
1. innervates the flexors of the foot and plantar flexion of the ankle; lesions affect plantar flexion of ankle and flexion of toes
-The muscular branch eventually gives off the tibial nerve and common fibular nerve, which innervates the muscles of the (lower) leg. The tibial nerve goes on to innervate all muscles of the foot except the extensor digitorum brevis (which is innervated by the peroneal nerve).
1. sciatic nerve (L45S123)
1. comprised of two main nerves – common peroneal (L45S12) and tibial (L45S123)
1. peroneal most commonly injured
1. peroneal has two divisions: superficial and deep; if the superficial branch is involved then there will be hypalgesia on the anterolateral aspect of the foot
2. if the deep division is affected there will be weakness in dorsiflexion and inversion of the foot with a sensory loss between the web area of the first two toes
2. tibial nerve
1. innervates the flexors of the foot and plantar flexion of the ankle; lesions affect plantar flexion of ankle and flexion of toes
Since the Sciatic nerve is made up of nerve roots from L5 to S3, it is usually the case that only one nerve root is compressed and therefore pain may not be in the entire back of the leg but only in part of this region
No comments:
Post a Comment