Download lumbo sacral plexus, cutaneus nerves, dermatome, mapping

LUMBO SACRAL PLEXUS, CUTANEUS
NERVES, DERMATOME, MAPPING
LEARNING OBJECTIVES
At the end of the lecture, the student should be able to:

Discuss the formation of lumbar plexus.

List the branches of lumber plexus with their root values.

Discuss relation of the nerves with psoas major muscle.

Structures supplied by lumbar plexus.

Know the formation of sacral plexus.

Describe the composition and relations of sacral plexus.

Enumerate branches of this plexus.

Discuss the cutaneous supply of lower limb.

Discuss few applied points about these plexuses.
INTRODUCTION

Somatic motor and general
sensory innervation of the
lower limb is by peripheral
nerves emanating from the
lumbar and sacral plexuses
on the posterior abdominal
and pelvic walls

These plexuses are formed
by the anterior rami of L1 to
L3 and most of L4 (lumbar
plexus) and L4 to S5 (sacral
plexus).

Nerves originating
from the lumbar and
sacral plexuses and
entering the lower
limb carry fibers from
spinal cord levels L1
to S3
Nerves from lower
sacral segments
innervate the
perineum.


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Terminal nerves exit the abdomen and pelvis through a
number of apertures and foramina and enter the limb.

Lumbar and upper sacral
nerves are tested clinically
by examining the lower limb.

As a consequence of this
innervation, lumbar and
upper sacral nerves are
tested clinically by
examining the lower limb
In addition, clinical signs (such as pain, 'pins and needles',
paresthesia, and fascicular muscle twitching) resulting
from any disorder affecting these spinal nerves (e.g.
herniated intervertebral disc in the lumbar region) appear
in the lower limb.
LUMBAR PLEXUS:
The lumbar plexus is formed by the anterior rami of nerves
L1 to L3, and most of the anterior ramus of L4 and
 It also receives a contribution from the T12 (subcostal)
nerve


Branches of the lumbar plexus include
 The
Iliohypogastric
 Ilio-Inguinal
 Genitofemoral
 Lateral
Cutaneous Nerve Of Thigh
(Lateral Femoral Cutaneous)
 Femoral,
And
 Obturator
Nerves
Division
Name
Roots
Target
Main
Iliohypogastric
nerve
1L
Skin over the lateral gluteal region
and above the pubis
Main
Ilioinguinal
nerve
1L
Skin over the root of the penis and
upper part of the scrotum (male),
skin covering the mons pubis and
labium majus (female)
Main
Genitofemoral
nerve
1, 2 L
Cremaster muscle
Dorsal
Lateral femoral
cutaneous
2, 3 L.
Skin on the lateral part
Venttral
Obturator nerve
(and Accessory
obturator nerve,
when present
2, 3, 4 L
Medial compartment of
Dorsal
Femoral nerve
2, 3, 4 L
Anterior compartment of thigh

The lumbar plexus forms in the substance of the psoas
major muscle anterior to its attachment to the transverse
processes of the lumbar vertebrae.

Relative to the psoas major muscle the various branches
emerge either:
 Anterior
Genitofemoral Nerve;
 Medial
Obturator Nerve;
 Lateral
Iliohypogastric,Ilio-
Inguinal, And

Femoral Nerves, And
 The
Lateral Cutaneous Nerve Of
The Thigh.
ILIOHYPOGASTRIC AND ILIO-INGUINAL NERVES
(L1)
The iliohypogastric and ilioinguinal nerves arise as a
single trunk from the anterior
ramus of nerve L1
 Either before or soon after
emerging from the lateral
border of the psoas major
muscle, this single trunk
divides into the iliohypogastric
and the ilio-inguinal nerves.

THE ILIOHYPOGASTRIC NERVE


It passes across the anterior surface of the quadratus lumborum
muscle, posterior to the kidney
It pierces the transversus abdominis muscle and continues
anteriorly around the body
between the transversus
abdominis and internal
oblique muscles
 Above the iliac crest, a lateral
cutaneous branch pierces the
internal and external oblique
muscles to supply the
posterolateral gluteal skin
 The remaining part of the
iliohypogastric nerve (the
anterior cutaneous branch)
continues in an anterior
direction, piercing the internal
oblique just medial to the
anterior superior iliac spine.


Becoming cutaneous, just
above the superficial
inguinal ring, after piercing
the aponeurosis of the
external oblique, it
distributes to the skin in
the pubic region
Throughout its course, it
also supplies branches to
the abdominal
musculature.
THE ILIO-INGUINAL NERVE
It is smaller than, and inferior to, the iliohypogastric nerve
as it crosses the quadratus lumborum muscle
 Near the anterior end of the iliac crest, it pierces the
transversus abdominis muscle, and then pierces the
internal oblique muscle and enters the inguinal canal.


It emerges through the superficial inguinal ring, along with
the spermatic cord, and provides cutaneous innervation to
the upper medial thigh, the root of the penis, and the
anterior 1/3rd of the scrotum in men, or the mons pubis and
labium majus in women

Throughout its course, it also supplies branches to the
abdominal musculature
THE GENITOFEMORAL NERVE
It arises from the anterior rami of the nerves L1 and L2
(ventral rami)
 It emerges on the
anterior surface of
psoas major
 Then descends on the
surface of the muscle,
in a retroperitoneal
position
 Eventually it divides
into genital and femoral
branches




The genital branch
continues downward and
enters the inguinal canal
through the deep inguinal
ring
In men, it innervates the
cremasteric muscle and
terminates on the skin in the upper anterior part of the scrotum
in women, it accompanies the round ligament of the uterus and
terminates on the skin of the mons pubis and labium majus
The femoral branch descends on the lateral side of the
external iliac artery and passes posterior to the inguinal
ligament, entering the femoral sheath lateral to the femoral
artery
 It pierces the anterior layer of the femoral sheath and the
fascia lata to supply the skin of the upper anterior thigh

LATERAL CUTANEOUS NERVE OF THIGH (L2
AND L3)




It arises from the anterior rami of nerves L2 and L3 (dorsal
divisions)
It emerges from the lateral border of the psoas major muscle,
passing obliquely downward across the iliacus muscle towards the
anterior superior iliac spine
It passes posterior to the inguinal ligament and enters the thigh
It supplies the skin on the anterior and lateral thigh to the level of
the knee
LUMBOSACRAL TRUNK



Formed by the union of the descending branch of nerve L4 with
nerve L5( ventral rami).
It enters the lesser pelvis by passing over the lateral part of the ala
of the sacrum, posterior to the common iliac vessels and the medial
part of the psoas
In the pelvis, it takes part in the formation of the sacral plexus
SACRAL PLEXUS
In human anatomy, the sacral plexus is a nerve plexus emerging
from the sacral vertebrae (S1-S4), and which provides nerves for the
pelvis and lower limbs.
COMPOSITION OF SACRAL PLEXUS

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The sacral plexus is formed by:
The lumbosacral trunk
The anterior division of the first sacral nerve
Portions of the anterior divisions of the second and third sacral
nerves
Its constituent nerves divide into anterior and posterior division.

The nerves forming the sacral plexus converge toward the
lower part of the greater sciatic foramen, and unite to form
a flattened band, from the anterior and posterior surfaces
of which several
branches arise.

The band itself is
continued as the sciatic
nerve, which splits on
the back of the thigh
into the tibial nerve and
common fibular nerve;
these two nerves
sometimes arise
separately from the
plexus,.
Often, the sacral plexus
and the lumbar plexus
are considered to be
one large nerve plexus,
the lumbosacral plexus.
The lumbosacral trunk
connects the two plexuses.

RELATIONS OF THE SACRAL PLEXUS:


Dissection of side wall of pelvis showing sacral and pudendal
plexuses.
The sacral plexus lies on the back of the pelvis between the
piriformis muscle
and the pelvic
fascia.
 In front of it are the
internal iliac artery,
internal iliac vein,
the ureter, and the
sigmoid colon.
 The superior
gluteal artery and
vein run between
the lumbosacral
trunk and the first
sacral nerve, and
the inferior gluteal
artery and vein between the second and third sacral nerves
BRANCHES OF SACRAL PLEXUS
Its branches total around a dozen, six from the nerves
before they divide, and three each from anterior and
posterior divisions.
 The six branches from the
main nerves all come from
sacral segments and all have
initial ‘P’.

BRANCHES FROM ANTERIOR RAMI:

S1,2- Nerves to piriformis

S2,3- Perforating cutaneous

S2,3- Posterior femoral cutaneous

S2,3,4- Pelvic splanchnic nerves

S2,3,4- Pudendal

S4- Perineal branch.
BRANCHES FROM ANTERIOR DIVISION OF
ANTERIOR RAMI
L4,5,S1- Nerves to quadratus femoris
 L5,S1,2- Nerves to obturatuor internus
 L4,5,S1,2,3- Tibial part of the sciatic

BRANCHES FROM POSTERIOR DIVISION OF
ANTERIOR RAMI
L4,5,S1- Superior gluteal
 L5,S1,2- Inferior gluteal
 L4,5,S1,2- Common peroneal
part of sciatic.

NERVES FORMED
All the nerves entering the plexus, with the exception of the third
sacral, split into ventral and dorsal divisions,
SCIATICA AND SCIATIC NERVE PAIN
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Sciatica is a layman's term for a
pinched nerve that can cause pain that
runs from the buttocks down the back
of the leg.
The sciatic nerve is about an inch or so
long in the buttocks made of multiple
spinal nerves.
When people commonly refer to
sciatica it is not necessarily a problem
of the sciatic nerve, it's a problem of the
nerve when it is being pinched as it
exits from the spine from a herniated
disc or a bone spur.
CUTANEOUS SUPPLY OF LOWER LIMB: