•The Sciatic nerve is the largest nerve in the Human Body and is the continuation of the main part of the Sacral Plexus.
•The rami (branches) converge at the inferior border of the piriformis to form the sicatic nerve.
•The sciatic nerve is the lateral most structure emerging from the Greater sciatic foramen.
Course of the nerve
•The nerve enters the gluteal region via the greater sciatic foramen inferior to piriformis and deep to gluteus maximus;
•Descends in posterior thigh deep to biceps femoris;.
•The sciatic is really two nerves, the tibial nerve, and the common fibular nerve, which are loosely bound together in the same connective sheath.
Nerve roots and Branches
•Anterior and posterior divisions of rami of L4-S3.
•The tibial nerve, derived from anterior divisions of the anterior rami .
•The common fibular nerve, derived from the posterior divisions of the anterior rami.
The common fibular nerve is also known as the peroneal nerve
Where does it Bifurcate???
•Bifurcates into tibial and fibular nerves at apex of popliteal fossa/distal thigh.
•However in about 12% of people, the nerve bifurcates as they leave the pelvis.
•In this case the tibial nerve passes inferior to piriformis and the common fibular nerve pierces this muscle or passes superior to it.
•In 0.5% of cases the peroneal nerve passes superiorly to the piriformis muscle.
Innervations of Sciatic nerve
•Does Not supply muscles in Gluteal region!!!!!
•Supplies all Hamstring Muscle.
–Semitendinosus
–Semimembranosus
–Biceps Femoris
•Main action of the Hamstrings are the extension of the thigh and the hip and flexion of the leg at the knee.
•Also innervates the Hamstring part of the Adductor Longus.
•This also helps with the extension of the thigh.
Innervations of Peroneal nerve
•The peroneal nerve supplies skin on lateral part of posterior aspect of leg via the lateral sural cutaneous nerve;
•Also supplies knee joint via its articular branch.
•Also the skin of the web between the great and 2nd toe via the Deep fibular nerve.
•The superficial fibular nerve innervates the skin of the anterolateral leg and dorsum of foot excluding the web space.
•The muscles of the anterior and lateral compartment of the leg and foot is supplied by the peroneal nerve via the deep and superficial fibular nerves.
–Tibialis anterior, extensor digitorum longus, extensor halluics longus, fibularis tertius(DFL), fibularis longus, fibularis brevis(SFL)
Innervations of the Tibial nerve
•The tibial nerve supplies skin on medial part of posterior aspect of leg via the medial sural cutaneous nerve;
•The skin of medial and lateral sides of sole are innervated by the medial and lateral plantar nerve respectively. Their origin is the tibial nerve.
•The calcaneal nerve which has it origins from the tibial and sural nerves innervates the skin overlying the heel.
•All muscles of the posterior compartment of the thigh. tibial division provides all but short head of biceps, which is supplies by the fibular division.
•Also all muscles of the posterior compartment of leg and foot.
–Gastorcnemius, soleus, plantaris,(superficial muscles)
–Popliteus, flexor hallucis longus, flexor digitorum longus, tibial posterior (deep muscles)
•It also supplies all articular branches to all joints of the lower limb.
Revision of lower back
1. What type of joint is a facet joint??
2. What is the orientation of thoracic & lumbar facet joints? and how is this orientation related to function?
3. List the accessory ligaments of facet joints.
4. What type of joint is the intervertebral disc.
5.Where are they usually found?
6. What type of cartilage is involved?
7. What are the two major parts of the disc?
8. What is the centre of the disc a remnant of?
9. Where does a disc prolapse normally occur? Why?
10. Which disc is most likely to prolapse? Why?
11. Why do most young adults grow by a centimeter overnight?
Answers
1 Synovial joint
2 Thoracic (curved) coronal & lumbar sagittal
Allows thoracic rotation & increased lumbar flexion
•a) Thoracic
•The arc permits rotation(greatest degree of rotation) and some lateral flexion of the vertebral column
•b) Lumbar
• In the more sagittally oriented superior joints, the laterally facing facets of the inferior articular processes of the vertebra above are “gripped” by the medially facing facets of the superior processes of the vertebra below, thus facilitating flexion, extension and allowing lateral flexion but prohibiting rotation
3.Ligamenta flava, Interspinous ligaments, Supraspinous ligaments, Nuchal ligament,Intertransverse ligament
4. Symphyses (secondary cartilaginous joints
5. Between adjacent vertebrae bodies
6. Sandwich of hyaline cartilage within which there is a fibrocartilage.
7.Anulus fibrosus, nucleus pulposus
8. Notochord
9. Herniations of the nucleus pulposus usually extend posterior laterally.
Flexion of the vertebral column produces compression anteriorly and stretching or tension posteriorly, squeezing the nucleus pulposus further posteriorly toward the thinnest part of the annulus fibrosus. If the anulus fibrosus has degenerated, the nucleus pulposus may herniate into the vertebral canal and compress the spinal cord.
10. L4/L5
This is because the lumbar spine carries most of the body's weight. The lower back has a lot more motion than the thoracic spine and also carries all the weight of the torso, making it t
11. All day long gravity pushes down on our vertebrae, pushing water out from between our spinal disks. All this pressure can cause us to lose up to a centimeter off of our height during the day. At night, the water diffuses back between our disks, elongating us once again. Of course, since we are in a horizontal position, the force of gravity will not affect us negatively he most frequently injured area of the spine.
No comments:
Post a Comment