Functional Anatomy 1 - Lecture 9: Nervous System 2

plexi

intermediate neural structures between spinal nerves and terminal peripheral nerves

motor and sensory plexi of the somatic nervous system

• plexi that carry the somatosensory and somatomotor nerves

• lumbar, sacral

lumbosacral plexus

lumbar plexus

• L1-L4

sacral plexus

• L4-S4

lumbar plexus

• neural plexus formed from anterior rami of L1-L4

• forms anterior to lumbar transverse processes near proximal attachment of psoas major

• terminal branches will provide neural input and from the lower extremity

L1

iliohypogastric and ilioinguinal nerves level

L1-L2

genitofemoral nerve level

L2-L3

lateral femoral cutaneous nerve level

L2-L4

obturator and femoral nerves level

L4-L5

lumbosacral trunk level

• connection between lumbar and sacral plexus

I (twice) Get Lunch On Friday

lumbar plexus pneumonic

• iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, obturator, femoral

iliohypogastric nerve (L1)

sensory: abdominal skin superior to the pubis (lower abdomen); superior/lateral thigh

motor: internal oblique and transverse abdominis

ilioinguinal nerve (L1)

sensory: superior/medial thigh

motor: internal oblique and transverse abdominis

genitofemoral nerve (L1-L2)

femoral branch

• sensory only: superior/anterior thigh

genital branch

• sensory: scrotum/labia major

• motor: cremaster muscle

lateral femoral cutaneous nerve (L2-L3)

sensory: lateral thigh

obturator nerve (L2-L4)

medial to psoas major

• sensory: medial thigh

• motor: medial compartment of thigh

  • hip adductor muscles

femoral nerve (L2-L4)

• sensory: anterior thigh (anterior cutaneous branch) and medial lower leg (saphenous nerve)

• motor: anterior compartment of thigh

  • hip flexion and knee extension muscles

largest branch of the lumbar plexus

psoas major

reference point for lumbar plexus

sacral plexus

• neural plexus formed from anterior rami of L4-S4

• forms anterior to piriformis on posterior-lateral wall of pelvis

• terminal branches will go on to provide neural input to and from the lower extremity

SIPPS

how to remember nerves of sacral plexus

nerves of sacral plexus

• “lumbosacral trunk (L4-L5)”

• superior gluteal (L4-S1)

• inferior gluteal (L5-S2)

• posterior femoral cutaneous (S1-S3)

• pudendal (S2-S4)

• sciatic (L4-S3)

  • several small nerves to deep external rotator muscles of the hip

superior gluteal nerve

L4, L5, S1

• sensory: n/a

• motor: gluteus medius, gluteus minimus, tensor fascia latae

inferior gluteal nerve

L5, S1, S2

• sensory: n/a

• motor: gluteus maximus

posterior femoral cutaneous nerve

S1, S2, S3

• sensory: posterior and medial thigh, popliteal fossa, upper posterior leg

• motor: n/a

pudendal nerve

S2, S3, S4

• sensory: perineum region

• motor: perineum region

  • terminal sections of reproductive, urinary, and digestive tracts

sciatic nerve

L4, L5, S1, S2, S3

• largest nerve in the body

• consists of common peroneal (common fibular) and tibial nerves in one sheath

• motor:

  • posterior compartment of thigh

    • hamstring group (mostly tibial division)

  • lower leg and foot

    • branches of sciatic nerve (tibial, superficial peroneal, deep peroneal)

• sensory: lateral lower leg and foot

  • branches of sciatic nerve (superficial peroneal, deep peroneal, sural, tibial branches to foot)

nerves to deep external rotators of the hip

• nerve to quadratus femoris (inferior gemellus) (L4-S1)

• nerve to obturator internus (superior gemellus) (L5-S1/S2)

• nerve to piriformis (S1-S2)

arterial supply of the lower extremity

abdominal aorta → R common iliac a. → R external & R internal a. → R femoral a(from external)

external iliac artery

• becomes the femoral artery after passing deep to inguinal ligament

  • femoral and branches supply the hip and thigh

• femoral a. becomes popliteal a. after passing through adductor hiatus (adductor magnus) to posterior knee

• popliteal a. divides into posterior tibial a., anterior tibial a. and peroneal (fibular) a. to supply 3 compartments of lower leg

internal iliac artery

• 3 main branches to hip and gluteal region

  • obturator a

  • superior gluteal a

  • inferior gluteal a

venous return lower extremity

• most of lower extremity veins will parallel arteries

• superficial veins

  • great saphenous vein

    • to femoral vein

  • small saphenous vein

    • to popliteal vein