Spinal Nerves(lumber Sacral)

Systematic Anatomy

Anatomy Department of WHU

Ⅳ. Lumbar Plexus (Ⅰ) Formation

A part of the anterior branch of T12 Anterior branches of L1-L3 A part of the anterior branch of L4 (Ⅱ) Position: Behind the psoas major & in front of the transverse processes of the lumbar vertebrae.

T12 L1 L2 L3 L4 L5

Lumbosacral trunk

(Ⅲ) Branches of Lumbar Plexus Iliohypogastric nerve Cutaneous branch: Skin of the hypogastric region & medial part of the inguinal region. Muscular branch: Muscles of the lower part of the abdominal wall. illohypogastric n.

transversus abdominis(deep) Obliquus internus abdominis aponeurosis of the obliquus externus abdominis

superficial inguinal ring

psoas major quadratus lumborum

2. Ilioinguinal nerve Cutaneous branch: Skin of the inguinal region, scrotum /greater lip of pudendum.

psoas major quadratus lumborum

Muscular branch: Muscles of lower part of the abdominal wall. ilioinguinal n. transversus abdominis (deep) Obliquus internus abdominis aponeurosis of the obliquus externus abdominis

spermatic cord

scrotum superficial inguinal ring

3. Lateral femoral cutaneous nerve: skin of the anterior & lateral aspect of the thigh. LFCN

anterior superior iliac spine

4. Femoral nerve Quadriceps femoris M. B. Sartorius Pectineus C. B.

Skin of anterior & medial side of the thigh.

Saphenous nerve

inguinal ligament

iliacus femoral triangle

Skin of the medial side of the leg & foot. Saphenous nerve

C. → cutaneous B. → branch M. → muscular

5. Obturator nerve  Muscular branch: medial group muscles of the thigh & the obturator externus.  Cutaneous branch: skin of the medial side of the thigh. Obturator nerve

6. Genitofemoral nerve Cutaneous branch

Skin of the scrotum

Skin of the greater lip of pudendum Muscular branch→Cremaster

Genitofemoral n.

Ⅴ. Sacral plexus (Ⅰ) Formation

Part of anterior branch of L4

Anterior branch of L5 Lumbosacral trunk Anterior branches of the sacral n. (S1-S5) Anterior branch of the coccygeal n. (Co)

(Ⅱ) Position: In the lesser pelvis, before the piriformis & the sacrum, behind the iliac L vessels. 4 L 5 S 1 S2 S3 S4 S5 Co

piriformis

L

Lumbosacral trunk

L 4

S5 S 1

S2 S3 S 4 5

Coccygeal n.

Lumbosacral trunk

(Ⅱ) Branches of Sacral Plexus 1. Sciatic nerve

inferior gluteal n.

greater sciatic foramen Suprapiriform /infrapiriform

Biceps femoris piriformis

Distribution Semimembranosus Semitendinosus Branches

gluteus maximus

Tibial nerve Common peroneal nerve biceps femoris semimembranosus, semitendinosus popliteal fossa

There is tenderness on this line in the sciatica(Sciatic Neuralgia ).

Variation of Sciatic Nerve

1) Tibial nerve

medial malleolus

Muscular branch: to posterior compartment of the leg. Cutaneous branch: medial sural cutaneous nerve

Terminal branches Medial plantar nerve Lateral plantar nerve

medial and lateral plantar

Medial/ lateral sural cutaneo us n.

2) Common peroneal nerve Distribution: Muscles of the anterior & lateral compartment of the leg. Skin over lateral surface of the leg & dorsum of the foot.

Deep peroneal nerve: Lateral head of Gastrocnemius anterior tibial artery

 Anterior group of the muscles of the leg.  A small area of the skin between the 1st & 2nd toes.peroneal nerve: Superficial  Peroneal muscles.  Skin on the distal part of the anterolateral surface of the leg, the dorsum of the foot & toes.

Peroneal muscles. Skin on the distal part of the anterolateral surface of the leg, the dorsum of the foot & toes.

Anterior group of the muscles of the leg. A small area of the skin between the 1st & 2nd toes.

(2) Posterior femoral cutaneous nerve (posterior cutaneous nerve of thigh) Distribution: skin of the lower part of the gluteal region & posterior part of the thigh. (3) Superior gluteal nerve Distribution: gluteus medius, gluteus minimus & the tensor fasciae latae. (4) Inferior gluteal nerve Distribution: gluteus maximus & the skin over the lower part of the gluteal region

(5) Pudendal nerve Distribution: Muscles & skin of the perineum & the external genital organs. Anal nerve (inferior rectal nerve) Branches Perineal nerve Dorsal nerve of penis (clitoris)

Ischiorectal fossa

1) Anal nerve (inferior rectal nerve): sphincter ani externus & skin of the anus. 2) Perineal nerve: muscles of the perineum & the skin of the scrotum or the greate lip of pudendum. 1) Dorsal nerve of penis ( clitoris): skin of the penis ( clitoris) & the cavernous body.

Highlights 1. The formation, position & distribution of major branches (femoral n., obturator n.) of lumbar plexus. 2. The formation, position & distribution of major branches (pudendal n., sciatic n., tibial n. & common peroneal n.) of sacral plexus.

Assignments P460

Fig. Ⅵ-5-5

P466

Fig. Ⅵ-5-11

P470

Fig. Ⅵ-5-15

P473

Fig. Ⅵ-5-17