1. Lumbar and sacral plexuses

2. Nerve plexuses
Networks of successive ventral rami that exchange fibers (crisscross & redistribute)
Why would this be protective?
Mainly innervate the limbs
Thoracic ventral rami do not form nerve plexuses

3. Plexuses
Cervical
Brachial
Lumbar
Sacral

4. Lumbar plexus L1-L4 Lies within the psoas major muscle
Innervates anterior and medial muscles of thigh through femoral and obturator nerves respectively
Femoral nerve also innervates skin on anterior thigh (including quads) and medial leg

5. Diaphragm and posterior abdominal wall:
The psoas major and minor muscles, the quadratus lumborum
muscle. The lumbar plexus and its related nerves. 5

6. LUMBAR PLEXUS
Spinal nerves branching from the lumbar region of the cord form the lumbar plexus. Branches of this plexus stimulate muscles of the back, hip and thigh. The plexus also is responsible for sensation in the skin of the thighs, the pubic area and the external genitalia in males and females.

7. LUMBOSACRAL SPINAL CORD POSTERIOR VIEW
The area within the rectangle shows the lower portion of the spinal cord. The branches leaving the sacral region pass through the sacral foramina forming the sacral plexus.

9. Lumbar plexus L1 – L4 (+ L5) Ilioinguinal nerve Genitofemoral nerve
mostly sensory from skin of thigh & genitals
Genitofemoral nerve
mostly sensory from scrotum, labia majora, ant. Thigh
Femoral Nerve
to quadriceps, sartorius
29 Oct. 2012
Spinal-Nerves.ppt 9

10. 1- Obturator nerve (L2-L3-L4) 2- Femoral nerve (L2-L3-L4)
Lumbosacral plexus
Lumbar plexus (T12- L4):
1- Obturator nerve (L2-L3-L4)
2- Femoral nerve (L2-L3-L4)
3- Lumbosacral trunk (L4-L5)
7- subcostal nerve (T12)
8- iliohypogastric N. (T12-L1)
9- ilioinguinal N. (L1)
10- genitofamoral N. (L1-L2)
11- lateral cutaneous N. of the thigh (L2-L3) 10

11. Lumbar Plexus Femoral nerve Obturator nerve Lateral femoral cutaneous
Cutaneous branches
Thigh, leg, foot (e.g. saphenous nerve)
Motor branches
Anterior thigh muscles (e.g. quadriceps, sartorius, iliopsoas)
Obturator nerve
Sensory
Skin medial thigh; hip, knee joints
Motor
Adductor muscles
Lateral femoral cutaneous
Skin lateral thigh
Genitofemoral
Skin scrotum, labia major, anterior thigh
Cremaster muscle

12. Lumbar plexus (be able to label femoral, obturator and saphenous nerves)

13. SACRAL PLEXUS
Spinal nerves branching from the lumbar (L4 and L5) and sacral (S1, S2, S3 and S4) region of the cord form the sacral plexus. Nerves branching from this plexus innervate the limb and pelvic area. Because the lumbar and sacral plexuses are interconnected, they are sometimes referred to as the lumbosacral plexus.

14. Sacral plexus
L4-S4
Supplies muscles and skin of posterior thigh and almost all of the leg
Main branch is the large sciatic nerve, which consists of:
Tibial nerve – to most of hamstrings, calf and sole
Common fibular nerve – to muscles of anterior and lateral leg and skin
Other branches supply pelvic girdle (gluteus muscles) and perineum (pudental nerve)

15. Sacral plexus L4 – S4 Superior & inferior gluteal nerves Sciatic nerve
To gluteus muscles
Sciatic nerve
To hamstrings & other posterior thigh & leg muscles
Pudendal nerve
Sensory from penis, clitoris, labia minora, anus
29 Oct. 2012
Spinal-Nerves.ppt 15

16. Sciatic nerve (roots): L4 L5 S1 S2 S3
Lumbosacral plexus
Sacral plexus:
Sciatic nerve (roots): L4 L5 S1 S2 S3
*Sciatic nerve is the thickest nerve of body.
*It is composed of Common Peroneal and
Tibial nerves.
*Com. Peroneal: composed of dorsal rami
Tibial: composed of ventral rami
*L4+L5= Lumbosacral trunk
3- Lumbosacral trunk
4- Sciatic nerve
5- common peroneal N.
6- tibial N.
12- posterior femoral cutaneous nerve
13- pudendal nerve
14- superior gluteal nerve 16

17. Sacral plexus (L4-S4) Sciatic nerve (L4-S3) Tibial nerve
Motor to muscles of pelvis and lower extremity (gluteal, posterior femoral, lower leg & foot)
Sensory from posterior pelvis, posterior thigh, anterior, posterior & lateral leg
Sciatic nerve (L4-S3)
Tibial nerve
Common peroneal (fibular) nerve

19. SCIATIC NERVE
The sciatic nerve (astrerisk) is formed from spinal nerves arising from the lumbar (L4 and L5) and sacral (S1, S2 and S3) regions of the spinal cord. It passes into the thigh and lower leg supplying innervation of sensation and movement for the entire lower limb. When giving a gluteal intramuscular injection, it is important to inject into the gluteus medius muscle to avoid damage to this large nerve.

20. Sacral Plexus Sciatic Superior gluteal nerve Motor: Branches into:
Hamstring
Branches into:
Tibial nerve
Cutaneous
Posterior leg and sole of foot
Motor
Posterior leg, foot
Common fibular (peroneal) nerve
Anterior and lateral leg, dorsum foot
Lateral compartment, tibialis anterior, toe extensors
Superior gluteal nerve
Gluteus medius and minimus, tensor fasciae latae

21. Sacral Plexus (continued)
Inferior gluteal nerve
Motor
Gluteus maximus
Posterior femoral cutaneous nerve
Sensory
Inferior buttocks, posterior thigh, popliteal fossa
Pudendal nerve
External genitalia, anus
Muscles of perineum

23. The only one of the three that travel below the knee is the sciatic nerve.
The sciatic nerve branches into two nerve:
1. tibial nerve
2. common peroneal nerve
a. Superficial peroneal nerve
b. Deep peroneal nerve

24. Anterior compartment-
Extensors of the knee
Femoral Nerve
lateral
medial
femur
Medial compartment-
Adductors of the knee
Obturator Nerve
Posterior compartment-
Flexors of the knee
Sciatic Nerve

25. Motor Branches of the Femoral Nerve L2 L3 L4 Rectus femoris iliopsoas
pectineus
sartorius
Vastus lateralis
Vastus medialis
Vastus intermedius

26. Motor Branches of the Obturator Nerve Adductor brevis Adductor longus
gracilis
Adductus magnus

27. Motor Branches of the Sciatic Nerve Hamstrings Common peroneal nerve
Semitendinosis
Biceps femoris
semimembranosus
Hamstrings
Common peroneal nerve
Tibial nerve
Deep peroneal nerve
Superficial peroneal nerve
Anterior compartment of leg
Gastrocnemius and posterior compartment of the leg and foot
Lateral compartment of leg

28. Sacral plexus nerves:
(Be able to label sciatic, tibial and common fibular nerves)

29. Nerve plexuses (very) simplified….
Cervical plexus C1-5
Brachial plexus C5-T1
Lumbar plexus L1-4
Sacral plexus L4-S4
Diaphragm?
Phrenic nerve C3-5
Arm and forearm extensors?
Radial nerve
Medial hand?
Ulnar nerve
Lateral palm?
Median nerve
Quad?
Femoral nerve
Footdrop?
Common fibular/peroneal nerve
(branch of Sciatic nerve)

30. Dermatomes (innervation of skin)
(area of skin innervated by the cutaneous branches from a single spinal nerve is called a dermatome)
Reveal sites of
damage to spinal
nerves or spinal cord
Dermatomes (innervation of skin)