Chapter Five: The Lower Limb Lumbar and Sacral Plexuses

Question 1

Nerves of the lower limb originate in the

Answer 1

Lumbosacral Plexus

Question 2

Lumbosacral Plexus

Answer 2

• receives roots from T12 down to S4
• supplies the abdominal wall, pelvis and lower limb
• can be subdivided into lumbar plexus and sacral plexus

Question 3

Nerves of the lumbar plexus

Answer 3

• IH: iliohypogastric
• II: ilioinguinal
• GF: genitofemoral
• LCNT: lateral cutaneous
• Fe: femoral
• Ob: obturator
• LST: lumbosacral trunk

Question 4

Nerves of the sacral plexus

Answer 4

• LST: lumbosacral trunk
• SGN: superior gluteal nerve
• IGN: inferior gluteal nerve
• SS: sacral sciatic
• P: pudendal

Question 5

The lumbar plexus

Answer 5

• made up of roots T12 and L1-5
• can be subdivided into smaller, superior branches and the major, inferior branches

Question 6

Minor branches of the lumbar plexus

Answer 6

• have roots T12-L3 and each nerve is generated by adjacent roots
• T12 and L3 combine into a trunk which then bifurcates into the iliohypogastric and the ilioingual nerves
• these nerves supply the abdominal wall
• L1 and L2 supply the genitofemoral nerve
• L2 and L3 combine to service the lateral cutaneous nerve

Question 7

Major branches of the lumbar plexus

Answer 7

• femoral, obturator and lumbo-sacral trunk
• femoral and obturator nerves arise from L2, 3, 4
• Femoral from the posterior divisions, extends the knee
• obturator from the anterior divisions, adducts the thigh
• lumbo-sacral trunk L4,L5 carries both anterior and posterior divisions which do not interact but remain adhered to eachother
• trunk becomes part of the sciatic nerve joining sacral roots lower down

Question 8

Sacral plexus

Answer 8

• can be divided into major and minor components
• major components are the superior and inferior gluteal nerves, the sacral component of the sciatic nerve and the pudendal nerve

Question 9

Sacral plexus: superior gluteal

Answer 9

• roots L4, L5, S1

Question 10

Sacral plexus: inferior gluteal

Answer 10

• roots L5, S1, S2

Question 11

Sacral plexus: sacral sciatic

Answer 11

• roots S1, S2, S3

Question 12

Sacral plexus: pudendal

Answer 12

• roots S2, S3,S4

Question 13

Sacral plexus: sciatic nerve

Answer 13

• roots L4-S3
• in parallel to the brachial plexus and made up of anterior and posterior divisions
• two divisions =: tibial and common peroneal split behind the knee

Question 14

Sacral plexus: minor components

Answer 14

• services most of the lateral rotators except obturaror externus

Question 15

Sacral plexus: minor components Obturator internus and gemellus superior

Answer 15

• L4, L5, S1, S2

Question 16

Sacral plexus: minor components gemellus inferior and quadratus femoris

Answer 16

L4, L5, S1

Question 17

Sacral plexus: minor components piriformis

Answer 17

• S1, S2