Lecture 5 - Lumbosacral plexus Flashcards
Lumbar plexus
Iliolingual nerve - L1 Genitofemoral nerve- L1,L2 Lateral femoral cutaneous nerve - L2,L3 Obturator nerve - L2,L3,L4 Femoral nerve - L2, L3, L4
What is the lumbar plexus formed from?
Anterior rami of the L1 - L4 spinal nerves
Iliolingual nerve
L1
Innervates skin of genitalia and upper medial thigh
Genitofemoral
L1, L2
Divides into the genital and femoral branch
Femoral branch innervates the upper anterior thigh
Lateral femoral cutaneous nerve
Posterior divisions of the L2, L3
Purely sensory
Enters thigh at lateral region of inguinal ligament
Supplies the anterolateral thigh to knee
Obturator nerve
Anterior divisions of L2,L3,L4
Innervates skin over the medial thigh
Motor nerve to medial compartment of thigh
Muscles innervated by the obturator nerve
Obturator externus Pectineus Adductor longus Adductor brevis Adductor magnus Gracilis
Femoral nerve
Posterior divisions of L2,L3,L4
Innervates anterior thigh via lateral cutaneous femoral branch
Saphenous branch - innervates skin of the medial leg
Motor innervation to anterior compartment of the thigh
Muscles innervated by the femoral nerve
Iliacus Pectineus Sartorius Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius
What is the sacral plexus formed from?
Anterior rami of S1, S2, S3, S4, S5
And contribution from L4 and L5 from lumbosacral trunk
Sacral plexus
Superior gluteal nerve - L4, L5, S1 Inferior glutal nerve - L5, S1, S2 Sciatic nerve - L4, L5, S1 , S2, S3 Posterior femoral - S1, S2, S3 Pudendal - S2, S3, S4
Superior gluteal nerve
L4, L5, S1
Leaves the pelvis via the greater sciatic foramen
Enters gluteal region above the piriformis
Accompanied by the sciatic artery and vein
Motor innervation to:
- Gluteus medius
- Gluteus minimus
- Tensor fascia lata
Inferior gluteal nerve
L5, S1, S2
Leaves the pelvis via the greater sciatic foramen
Enters gluteal region BELOW the piriformis
Accompanied by the inferior gluteal artery and vein
Motor innervation to:
- Gluteus maximus
Sciatic nerve
Longest nerve in body L4, L5, S1, S2, S3 No branches in gluteal region Emerges transversely from the pelvic cavity midway between the posterior superior iliac spine and ischial tuberosity Under the piriformis
In posterior thigh:
- lies on the posterior surface of the adductor magnus
- crossed by long head of the biceps femoris
Divides into:
- tibial nerve
- common fibular (peroneal) nerve
(at the superior end of the popliteal fossa)
Tibial nerve
Motor innervation to hamstrings:
- Semitendinosus
- Semimembrinosus
- Biceps femoris long head
- Ischial part oft the adductor magnus
Common peroneal nerve
Motor innervation to:
- Biceps femoris short head
Posterior cutaneous nerve of the thigh
Posterior divisions of S1, S2
Anterior divisions of S2, S3
Leaves the pelvis via the greater sciatic foramen under the piriformis
Innervates the skin of the posterior thigh and leg
Which structures exit the pelvis inferior to the piriformis?
Inferior gluteal nerve, artery and vein Sciatic nerve Posterior femoral cutaneous nerve Nerve to quadratus femoris Nerve to obturator internus Pudendal nerve, inferior pudendal artery and vein
Structures that pass through the lesser sciatic foramen
Nerve to obturator internus
Tendon of the obturator internus
Pudendal nerve
Internal pudendal vessels
Safe site for intramuscular injections in the gluteal region
Avoid sciatic nerve
Therefore upper, outer quadrant = dorsogluteal site (children over 3)
ventrogluteal site- 7yrs old to adults (further from neurovascular bundle but requires compliance)
How to locate the ventrogluteal region?
- Place palm over the greater trochanter
- Point thumb to inguinal region and index finger to ASIC
- Spread index and middle finger to make V
- Inject between the proximal interphalangeal joints into
the gluteus medius
