Download TSM85 - Innervation of the Lower Limbs

TSM85: INNERVATION OF THE LOWER LIMB
21/11/08
LEARNING OUTCOMES
Outline the pattern of blood supply to the lower limb
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At L4 (2cm below the umbilicus) the abdominal aorta bifurcates into the two common iliac arteries
o At the pelvic inlet the common iliac arteries divide into internal and external iliac arteries
o The external iliac becomes the femoral artery distal to the inguinal ligament
The femoral artery descends the femoral canal to supply all of the structures of the lower limb
o Near the femoral head it gives off a large deep branch – profunda femoris
 This gives the lateral and medial circumflex arteries which supply the hip joint
 Three or four perforating arteries pierce adductor magnus to supply posterior thigh
o At the adductor hiatus it becomes the popliteal artery and descends to the posterior leg
 Gives off three genicular arteries which supply structures of the knee
o At the leg it divides into the anterior (central) and posterior (medial) tibial arteries
 The posterior branch immediately gives the (lateral) peroneal (fibular) artery
o The posterior tibial artery terminates as the medial and lateral plantar arteries on the
plantar surface of the foot
o The anterior tibial artery terminates as the dorsalis pedis artery on the dorsum of the foot
Outline the pattern of nerve supply to the lower limb
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The lower limbs are innervated by branches of the lumbar and sacral plexus
o Lumbar plexus (L1-L4)
 Femoral nerve – L2-L4 – supplies anterior thigh
 Obturator nerve – L2-L4 – supplies medial thigh
o Sacral plexus (L4-S4)
 Sciatic nerve – L4-S3 – supplies posterior thigh
 Tibial nerve – branch of sciatic – supplies posterior leg
 Superficial fibular nerve – branch of sciatic – supplies lateral leg
 Deep fibular nerve – branch of sciatic – supplies anterior leg
Sensory cutaneous nerve supply to the lower limb is:
o L1-L5 on the anterior thigh and leg
o Mostly S1-S4 on the posterior thigh and leg – two axial lines down the posterior lower limb
Describe the formation, course and major divisions of the sciatic nerve
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The sciatic nerve is the largest nerve in the body and originates from L4 to S3
o Passes through the greater sciatic foramen into the pelvis
o At its origin supplies the gluteal muscles, obturator internus and quadratus femoris
o Supplies the posterior thigh (hamstring muscles)
o Divides into tibial and two fibular nerves at the knee
o These supply the posterior, lateral and anterior leg respectively