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SCIATIC NERVE
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INTRODUCTION
Sciatic nerve is thethickest, largest and the
longest nerve of the body.
It is also known as
ISCHIATIC NERVE. It begins in the pelvis and
terminates at the superior
angle of the popliteal
fossa by dividing into thetibial and common
peroneal nerves.
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ORIGIN AND ROOT VALUE
Its the terminal branch or
the continuation of thesacral plexus.
Its root value isL4,L5,S1,S2,S3.
Its is made up of 2 parts,tibial and the commonperoneal parts.
TIBIAL PART-Ventraldivisions of the anteriorprimary rami of
L4,L5,S1,S2,S3. COMMON PERONEAL
PART-Dorsal divisions of theanterior primary rami ofL4,L5,S1,S2,S3.
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COURSE AND ITS DISTRIBUTION
IN PELVIS
IN GLUTEAL REGION
IN THIGH
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IN PELVIS
Arises in the pelvis. Leaves the pelvis by
passing through greater
sciatic foramen below the
piriformis to enter thegluteal region.
No branches.
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IN GLUTEAL REGION
Enters the gluteal regionthrough greater sciaticforamen.
Here its course is b/wischial tuberosity and
greater trochanter withslight lateral convexity.
Lies deep to the gluteusmaximus and superficial toobturator internus with two
gamelli and quadratusfemoris and then enter theback of the thigh.
No branches.
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BACK OF THIGH
Enters the back of thethigh at the lower borderof gluteus maximus.
Nerve is superficial toadductor magnus and
deep to long head ofbiceps femoris.
Here it gives muscularbranches to
semitendinosus,semimembranosus, bicepsfemoris and ischial headof adductor magnus.
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TERMINATION
Terminates at the superior angle of the popliteal fossa i.e.at the junction of upper 2/3rd and lower 1/3rd of the
thigh.
Terminal branches are tibial and common peroneal
nerves
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BRANCHES
ARTICULAR-Branches to thehip joint arise in gluteal
region.
MUSCULAR-Branches given
in the upper part of thigh.
1.Tibial part-supplies long
head of the biceps
femoris,semitendinosus,
semimembranosus.
2.Common peroneal part-
supplies short head of
biceps femoris.
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SEMITENDINOSUS
ORIGIN: From the inferomedial impression on the upperpart of ischial tuberosity
INSERTION: Upper part of the medial surface of the tibia
behind sartorius and gracilis
ACTION: Flexor of the knee
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SEMIMEMBRANOSUS
ORIGIN: Superolateral impression on the upper part ofthe ischial tuberosity
INSERTION: Into the groove on the posterior surface of
the medial condyle of tibia
ACTION: Flexor of the knee
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BICEPS FEMORIS
ORIGIN:1.LONG HEAD: From the inferomedial impression on the
upper part of the ischial tuberosity
2.SHORT HEAD: From the lateral lip of linea aspera b/w
add.magnus and vastus lat. INSERTION: Head of the fibula
ACTION: Flexor of the knee.
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ADDUCTOR MAGNUS
HAMSTRING PART: ORIGIN: Tuberosity of ischium.
INSERTION: Linea aspera and adductor tubercle on
medial cndyle of the femur.
ACTION: Extension of hip joint.
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SENSORY DISTRIBUTION
Innervates the skin ofpost. Aspect of thigh and
gluteal regions
Entire lower leg except forits medial aspect
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APPLIED ANATOMY
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Sciatica
Sciatica (or sciatic neuritis) is a set of symptomsincluding pain that may be caused by general compression
and/or irritation of one of five spinal nerve roots that give
rise to each sciatic nerve, or by compression or irritation of
the left or right or both sciatic nerves. The pain is felt in the
lower back, buttock, and/or various parts of the leg and foot.
In addition to pain, which is sometimes severe, there may be
numbness, muscular weakness, pins and needles or tingling
and difficulty in moving or controlling the leg. Typically, the
symptoms are only felt on one side of the body. Sciatica is a set of symptoms rather than a diagnosis for what
is irritating the root of the nerve, causing the pain.
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Region of pain by compression of following roots of
the sciatic nerve
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Sypmtoms
Sciatica causes pain, a burning sensation, numbness, ortingling radiating from the lower back and upper buttockdown the back of the thigh to the back of the leg. Theresult is leg pain.
Sometimes the pain radiates around the hip or buttock tofeel like hip pain. While sciatica is often associated with lower backpain (lumbago), it can be present without low back pain. Severe sciatica can make walking difficult if not
impossible.
Sometimes the symptoms of sciatica are aggravated bywalking or bending at the waist and relieved by lyingdown.
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Who is prone to developing symptoms of sciatica?
Sciatica can affect just about anyone, but it is extremelyuncommon in young patients. Sciatica typically affects 30
to 50 year old patients. Often there is a sudden onset that
may be attributed to over-exertion or a back injury.
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Causes
Spinal disc herniation
Spinal stenosis
Trigger points
Piriformis syndrome
Pregnancy
Habits
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Spinal disc herniation
Herniation of a disc occurs when the liquid center of the disc
bulges outwards, tearing the external ring of fibers, extrudes intothe spinal canal, and compresses a nerve root against the lamina orpedicle of a vertebra, thus causing sciatica. This extruded liquidfrom the nucleus pulposus may cause inflammation and swelling ofsurrounding tissue which may cause further compression of the
nerve root in the confined space in the spinal canal. Sciatica caused by pressure from a disc herniation and swelling of
surrounding tissue can spontaneously subside if the tear in the discheals and pulposis extrusion and inflammation cease
Sciatica can be caused by tumours impinging on the spinal cord or
the nerve roots. Severe back pain extending to the hips and feet, lossof bladder or bowel control, or muscle weakness, may result fromspinal tumours. Trauma to the spine, such as from a car accident,may also lead to sciatica.
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Sciatica due to herniated spinal disc
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Spinal stenosis
Spinal stenosis, a condition in which the spinal canal (thespaces through which the spinal cord runs) narrows and
compresses the sciatic nerve roots.
This narrowing can be caused by bone spurs,
spondylolisthesis, inflammation, or herniated disc whichdecreases available space for the spinal cord, thus
pinching and irritating nerves from the spinal cord that
travel to the sciatic nerves.
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Spinal stenosis Pain shooting down the sciatic
nerve
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Piriformis syndrome
In 15% of the population, the sciatic nerve runs throughthe piriformis muscle rather than beneath it.
When the muscle shortens or spasms due to trauma oroveruse, it can compress or strangle the sciatic nerve beneaththe muscle. Conditions of this type are generally referred to as
entrapment neuropathies; in the particular case of sciaticaand the piriformis muscle, this condition is knownas piriformis syndrome.
It has colloquially been referred to as "wallet sciatica" sincea wallet carried in a rear hip pocket will compress the
muscles of the buttocks and sciatic nerve when the bearer sitsdown.
Piriformis syndrome may be a cause of sciatica when thenerve root is normal.
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http://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Neuropathyhttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Walletshttp://en.wikipedia.org/wiki/Walletshttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Piriformis_syndromehttp://en.wikipedia.org/wiki/Neuropathyhttp://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Piriformis_musclehttp://en.wikipedia.org/wiki/Piriformis_muscle7/28/2019 Siatic Nerve
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Trigger points
Another source of sciatic symptoms is active triggerpoints of the lower back and the gluteus muscles. In thiscase, the referred pain is not consequent to compressionof the sciatic nerve, though the pain distribution downthe buttocks and leg is similar.
Trigger points occur when musclesbecome ischemic (having low blood flow) due to injuryor chronic muscular contraction.
The most commonly associated muscles with trigger
points triggering sciatic symptoms are: the quadratuslumborum, thegluteus medius, thegluteus minimus, andthe deep hip rotators.
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http://en.wikipedia.org/wiki/Ischemiahttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_minimushttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Gluteus_mediushttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Quadratus_lumborumhttp://en.wikipedia.org/wiki/Ischemia7/28/2019 Siatic Nerve
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Pregnancy
Results from
the uterus pressing on
the sciatic nerve, and,
secondarily, from the
muscular tension and/or
vertebral compression
consequent to carrying
the extra weight of
the fetus, and the postural
changes inherent to
pregnancy
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Habits
Sitting on a wallet or
standing for prolongedperiods of time every daywhich can cause self-inflicted sciatica. Symptomsof numbness and/or pain
behind the knee cap areassociated with this form ofsciatica.
Work-related sciatica maybe caused by the use of toolbelts which hang around thehips and cause significantmisalignment of the sacralvertebrae over long timeperiods.
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There is a condition where the
nerve becomes compressed as itpasses under a muscle in the hipthat results in the nerve sendingpain messages to the brain thatin many cases are phantompains. Phantom pains from
sciatica will give the impressionthat the only place where pain isoccurring is in the heels of thefeet and there is no pain in theknee or lower leg area. Sciaticais associated with a feeling of
numbness in the heel and maybe associated with a burningpain at night. Getting treatmentfor the Sciatica in many cases isthe cure for the heel pain.
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Reference
www.google.com
www.wikipedia.com
B.D Chaurasia
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THANK YOU
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