Formation

• Anterior (lumbar) part - formed by L4, L5, and L6; lies between the psoas muscles
• Posterior (sacral) part - formed by L6, S1, S2, and sometimes a branch of S3; lies on the pelvic face of the sacrosciatic ligament at the greater sciatic foramen

Nerves of the Lumbar Plexus (Anterior Part)

1. Iliohypogastric Nerve (L1, L2)

• Runs along the sublumbar muscles
• Supplies skin and muscles of the flank and abdominal wall

2. Ilioinguinal Nerve (L2, L3)

• Runs parallel to the iliohypogastric
• Supplies the inguinal region and medial thigh skin; important in anesthesia of the scrotum/udder region

3. Genitofemoral Nerve (L3, L4)

• Two branches: genital and femoral
• Genital branch - supplies the prepuce/scrotum (males) or udder (females)
• Femoral branch - supplies skin of the medial thigh

4. Lateral Cutaneous Femoral Nerve (L4, L5)

• Arises from ventral branches of L4 and L5
• Passes caudally between the psoas muscles
• Runs along the deep face of the subiliac lymph node
• Supplies the skin of the lateral thigh (stifle region)

5. Femoral Nerve (L4, L5 - strongest of the lumbar plexus; some sources: L5, L6)

• The largest nerve of the anterior part
• Runs downward and backward between the psoas muscles
• Crosses the lateral face of the tendon of psoas minor
• Goes under cover of sartorius, lies on iliopsoas, detaches the saphenous nerve
• Dips between rectus femoris and vastus medialis
• Supplies: quadriceps femoris (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius) and articularis genu
• Saphenous nerve (branch): passes down the femoral canal between sartorius and vastus medialis; supplies sartorius, gracilis, and skin of the medial leg

6. Obturator Nerve (L4, L5, L6 - all three lumbar nerves of the plexus)

• Passes downward and backward across the iliacus
• Runs on the medial surface of the ilium (covered by peritoneum)
• Turns downward toward obturator internus
• Passes through the obturator foramen and through obturator externus
• Supplies: pectineus, adductor magnus, gracilis, obturator externus
• Clinically very important - obturator nerve paralysis in cows after dystocia causes inability to adduct hind limbs ("doing the splits")

7. Iliopsoas Nerve (L4)

• Short branch supplying psoas major, psoas minor, and iliopsoas muscles

Nerves of the Sacral Plexus (Posterior Part)

1. Cranial Gluteal Nerve (L6, S1)

• Anterior of the nerves from the posterior part; lies in front of the sciatic nerve
• Exits through the greater sciatic foramen with the cranial gluteal vessels
• Divides into 4-5 branches supplying: gluteus medius and gluteus profundus (deep gluteus)

2. Caudal Gluteal Nerve (S1, S2)

• Exits behind the sciatic nerve through the greater sciatic foramen
• Supplies: gluteus superficialis (biceps femoris), semitendinosus, semimembranosus

3. Sciatic Nerve / Ischiatic Nerve (L5, L6, S1, S2 - largest nerve in the body)

a. Tibial Nerve (Caudal branch)

• Continues down the caudal aspect of the thigh
• Passes between the heads of gastrocnemius
• Supplies: biceps femoris, semitendinosus, semimembranosus, gastrocnemius, soleus, popliteus, deep digital flexors
• Divides into medial and lateral plantar nerves supplying the plantar aspect of the foot

b. Common Fibular (Peroneal) Nerve (Cranial branch)

• Detached about the middle of the thigh; lies in front of the sciatic
• Descends to origin of gastrocnemius, crosses obliquely over the lateral head
• Gives off: lateral cutaneous nerve of the leg (supplies skin of stifle region, perforates biceps femoris)
• Branches to biceps femoris
• Divides at the level of the lateral digital extensor into:
  • Superficial fibular (peroneal) nerve - skin of dorsum of foot
  • Deep fibular (peroneal) nerve - extensor muscles of the digit

4. Pudendal Nerve (S2, S3, S4)

• Exits through the lesser sciatic foramen
• Supplies: anal and urethral sphincters, skin of the perineum, penis/clitoris and prepuce, vulva
• Important for pudendal nerve block in obstetric and reproductive procedures in cattle

5. Pelvic Nerve (Nervus Pelvinus) (S2, S3, S4)

• Parasympathetic nerve (pelvic splanchnic nerves)
• Carries preganglionic parasympathetic fibers to the pelvic viscera (bladder, rectum, uterus, vagina)

Summary Table

Clinical Relevance in Ox

• Obturator nerve paralysis - the most common nerve injury in cattle; results from compression during dystocia (difficult calving), causing "cow-splitter" posture with inability to adduct hind legs
• Sciatic nerve damage - can result from injections in the gluteal region or trauma; causes knuckling of the fetlock and loss of extensors
• Pudendal nerve block - used clinically in bulls for penile relaxation during surgery, and in cows for perineal/reproductive procedures
• Femoral nerve injury - causes quadriceps paralysis; the animal cannot extend the stifle and cannot bear weight