Anatomy of lumbosacral plexus (by Murtaza Syed)

Anatomy of Lumbosacral Plexus.

1. ANATOMY OFANATOMY OF
LUMBO-SACRAL PLEXUSLUMBO-SACRAL PLEXUS
By: Syed Irshad Murtaza
Technologist.
Neurophysiology Dept.
AKUH Karachi.
12-08-2014
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2. OutlineOutline
•Spinal cord.
•Lumbar plexus anatomy
•Sacral plexus anatomy
•Components of lumbosacral plexus
•Key for the L.S Plexus
•Key to draw L.S Plexus.
•Terminal Branches of L.S plexus.
•Motor and Sensory Distribution.
•Questions.
•References
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3. Spinal cord Spinal cord
•Lumbar and sacral
enlargement. .. The sites
where the nerves serving the
lower limbs, emerge.
•Conus Medullaris:
•The terminal portion of the
spinal cord
•Cauda equina:
•The collection of nerve roots
at eh inferior end of the
vertebral canal.
•Spinal cord ends at the level
of L2 vertebrae (adults).
•Spinal nerves 31 pairs
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6. Lumbosacral plexusLumbosacral plexus
Lumbosacral plexus is basically combination of two
plexus,
Lumbar Plexus &
Sacral Plexus.
1.LUMBAR PLEXUS:
The lumbar plexus is formed by the ventral rami of first
four lumber nerve roots (L1, L2, L3 (major) & part of L4).
In 50% of cases it receives a contribution from the
ventral rami of last thoracic root (T12).
It lies within the substance of the posterior part of psoas
major muscle, anterior to the transverse processes of
the lumbar vertebrae. The branches emerge to both
lateral and medial sided of psoas major muscles.
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7. •"iliopsoas" are referred to
as the "dorsal hip muscles“

or "inner hip muscles.
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8. Components of lumbosacral plexusComponents of lumbosacral plexus
•Components of the lumbosacral plexus are as,
•1. Lumbar plexus L1, L2, L3, L4
•2. Lumbosacral Trunk L4, L5
•The above roots contribute in lumbar and sacral plexus
both.
•3. Sacral Plexus S1, S2, S3, S4
•Smaller branches of the lumber plexus innervate the
posterior abdominal wall and psoas muscles (psoas
major, iliacus).
•Main branches innervate the anterior thigh and their
relative muscles.
•Key to remember.
•Root →Branches→Divisions→Terminal Branches
• (RBDT)
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12. RBDTRBDT
•Root: these are constituted by the anterior primary
rami of L1, L2, L3, L4 (T12).
•Branches: L1 root gives an upper and lower branch
•L2 Root gives and upper and lower branch
•L3 does not give any branch
•L4 gives an upper and lower branch
•Division: Lower branch of L2, upper branch of L4 and
ventral rami of L3 nerve roots divide into small anterior
and large posterior division.
•From L2 and L3 each gives two and L4 one posterior
divisions, with single anterior division from all branches
(L2, L3, L4).
•Lower branch of L4 and L5 unite to form lumbosacral
trunk
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13. Terminal Branches of Lumbar PlexusTerminal Branches of Lumbar Plexus
•L1 unites with a small branch from T12 and splits into an upper and
lower branches.
•The upper larger branch divides into two:
•iliohypogastric (T12, L1) and ilioinguinal nerves (L1).
• The lower smaller branch of L1 unites with a branch from L2 to form
the genitofemoral nerve.
•The remainders of L2, L3 and L4 divide into ventral and dorsal
branches. Ventral (Anterior) divisions of L2, L3, L4 unite to form
obturator nerve.
•The dorsal (posterior) divisions of L2 and L3 divide into small and
larger parts. Smaller parts of dorsal divisions of L2 and L3 unite to
form the lateral femoral cutaneous nerve.
•Larger parts of dorsal divisions of L2 and L3 unite with L4 to form
femoral nerve.
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15. FEMORAL NERVEFEMORAL NERVE
•It is formed by the dorsal or posterior division of the
anterior rami of L
2,
L
3,
&

L
4
roots.
•The femoral nerve is the largest branch of the lumbar
plexus. It mainly supplies the extensors muscles of the
knee (quadriceps) (VL, VI, VM, RF).
•The Saphenous Nerve is a purely sensory nerve
which the largest and longest cutaneous branch of
the femoral nerve.
•Lateral femoral cutaneous nerve of the thigh
The lateral femoral cutaneous nerve of the thigh
emerges from the lateral border of psoas major
which is formed by the posterior divisions of L2 and
L3.
. It gives cutaneous supply to the lateral part of the
thigh.
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17. •KEY:
•Roots
•↓
•Branches
•↓
•Divisions
•↓
•Terminal
branches.
•R-B-D-T
•IIGOLF
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18. Sensory Distribution of the Lower Limb
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20. Lumbosacral Trunk & sacral plexus.
•The sacral plexus is formed by the lumbosacral trunk
(L
4
,L
5
), & ventral rami of S
1,
S
2,
S
3,
S
4
.
•Contribution of the fourth sacral ventral rami is partial &
the remainder of the last (S
5
) joins the coccygeal plexus.
•Key to remember sacral plexus:
•Root  Divisions Terminal Branches (R.D.T/B)
•Roots: These are constituted by the anterior primary
rami of L
4
, L
5,
S
1,
S
2,
S
3,
& S
4

•Divisions: The lower branch of L
4
ventral rami

& ventral
rami of L
5
, S
1
& S
2
give anterior and posterior divisions.
While S
3
forms & shares only anterior division .
•Terminal Branches: These anterior and posterior
divisions unite to form the terminal nerve branches.
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21. Terminal BranchesTerminal Branches
•The posterior division of L
4
,L
5
& S
1
joins to form Superior Gluteal
Nerve .
•The posterior divisions of L
5
,S
1
&

S
2
unites to form the Inferior Gluteal
Nerve.
•The posterior divisions of L
4
,L
5
,S
1
& S
2
joins to form Common fibular
or Peroneal Nerve. It’s the about one-half the size of the tibial
nerve.
•The anterior divisions of L
4
,L
5
,S
1
,S
2
& S
3
unites to form Poterior Tibial
Nerve.
•The anterior divisions of S
2
,S
3
& S
4
unites to form Pudendal Nerve.
•So both these nerves i.e. Tibial and peroneal run in a single
covering of sheath and called as Sciatic Nerve (L
4
,L
5
,S
1
,S
2
&S
3
) .
Which is the largest nerve of the body.
•
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22. Sciatic NerveSciatic Nerve
•Sciatic Nerve
descends along the
back of the thigh and
through the middle of
the popliteal fossa, to
the lower part of the
Popliteus muscle. It
divides just 5cm above
the politial fossa into
Common Peroneal &
Tibial nerves to supply
their relative muscles.
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23. Key to Draw sacral PlexusKey to Draw sacral Plexus
111221 Anterior
2332 Posterior
•SIPPP
•S. Superior Glutal Nerve (L4, L4, S1) Posterior
•I. Inferior Glutal Nerve (L5, S1, S2) Posterior
•P. Peroneal (common fibular) Nerve (L4,L5,S1,S2) Posterior
•P. Posterior Tibial Nerve (L4,L5,S1,S2,S3 )Anterior
•P. Pudendal Nerve. (S2, S3, S4) Anterior

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26. Sensory Distribution to the Legs:Sensory Distribution to the Legs:
•Superficial Peroneal: it’s the cutaneous branch from
the common peroneal nerve which supplies to the
anterio-lateral aspect of leg upto dorsum of the foot.
•Sural nerve formed by the junction of the medial
sural cutaneous (it is the sensory branch of tibial
nerve) with the peroneal anastomotic branch (its
branch of lateral sural cutaneous nerve), passes
downward near the lateral margin of the tendo-
calcaneous, lying close to the small saphenous vein,
to the interval between the lateral malleolus and the
calcaneous.
•It supplies to the posterio-lateral aspect of the leg
upto lateral malleolus.
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27. Nerve Name Origin Supplies
IliohypogastricT12,L1 Motor supply to internal oblique, transverses
muscles, sensation over lower anterior abdominal
wall
Ilioinguinal L1 Sensation over anterior pubis (mons) and anterior
scrotum or labia
Genitofemoral L1, L2 Genital branch: motor supply to cremastor muscle,
sensation to anterior scrotum; femoral branch:
sensation to anterior thigh
Femoral L2, L3, L4 Motor supply to extensors of the knee, sensation to
anterior thigh
Obturator L2, L3, L4 Motor supply to adductors of the thigh, sensation to
medial thigh
Lumbosacral trunkL4, L5 Joins the sacral nerves to form the lumbosacral
plexus that supplies motor and sensory innervations
to the lower extremities
Posterior femoral
cutaneous
S2, S3 Sensation to perineum, posterior scrotum, and
posterior thigh
Pudendal S2, S3, S4 Motor to levator ani, muscles of the urogenital
diaphragm, anal and striated urethral sphincter,
sensation to the perineum, scrotum, and penis
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28. 12/08/2014
Nerve Name Origin Supplies
Nerve to quadratus
femoris
L4,L5,S1
quadratus femoris, inferior gemellus
Superior gluteal L4,L5,S1 gluteus medius & minimus, tensor fasciae
latae
Inferior gluatel L5,S1,S2 Gluteus maximus
Nerve to obturator
internus
L5,S1,S2 obturator internus, superior gemellus
sciatic
sacral plexus
(ventral primary
rami of L4-L5, S1-
S3)
(via its tibial & common peroneal branches)
semitendinosus, semimembranosus, biceps
femoris, part of adductor magnus, muscles of
leg & foot
skin of leg & foot (excluding medial side of
leg & foot)
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32. ReferencesReferences
•Electromyography and neuromuscular disorders
•By David C. Preston
•Snell's Clinical Anatomy 9
th
Edi
•By Richard S. Snell
•Electrodiagnosis in Diseases of Nerve and Muscle:
Principles and Practice
•By Jun Kimura
•http://en.wikipedia.org/wiki/Sural_nerve
•http://en.wikipedia.org/wiki/Quadriceps_femoris_muscle
Thanks for the patienceThanks for the patience
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