L18_Lumbosacral Plexus Flashcards
Overall definition of the spinal cord
Cervical and lumbar enlargements correspond with plexuses involved in providing innervation to the limbs.
Cervical enlargement (Brachial Plexus C5-T1)
Lumbar enlargement (Lumbosacral Plexus L1-S4)
Explain how the lumbosacral plexus is separated
Lumbar plexus L1-L4:
- cutaneous innervation to the anterior and medial thigh, anterior knee and medial leg and foot.
- motor innervation to anterior and medial compartments of the thigh
Sacral plexus L4-S4:
- Cutaneous innervation to lower buttocks, posterior thigh and leg, lateral leg and majority of the foot.
- motor innervation to the gluteal region, posterior thigh compartments of the leg and foot
Tell me the nerves from the lumbosacral plexus
Lumbar plexus (L1-L4):
- Iliohypogastric nerve (T12-L1)
- Ilioinguinal nerve (L1)
- Genitofemoral nerve (L1-L2)
- Obturator nerve (L2-L4)
- Lateral Femoral Cutaneous nerve (L2-L3)
- Femoral nerve (L2-L4)
LUMBOSACRAL TRUNK (L4-L5) -> this nerve has origins from both the lumbar and sacral plexus and when they merge together that is what creates the lumbosacral plexus.
Sacral plexus (L5-S4):
- Superior gluteal nerve (L4-S1)
- Inferior gluteal nerve (L5-S2)
- Pudendal nerve (S2-S4)
- Posterior Femoral Cutaneous nerve (S1-S3)
- Sciatic nerve (L4-S3)
There are 3 spaces in the inguinal region. Explain where they are and what passes through it
- Muscular Compartment:
- Iliopsoas muscle
- Lateral Femoral Cutaneous nerve of the thigh
- Femoral nerve - Vascular Compartment:
- Femoral artery and vein
- Genitofemoral nerve (femoral branch) - Opening to Inguinal Canal
- Ilioinguinal nerve
- Genitofemoral nerve (genital branch)
- Spermatic cord (male), round ligament of uterus (female)
The inguinal canal is a fascial canal acing as a conduit between the internal and external pelvis
The Lumbar Plexus (L1-L4)
Describe the Iliohypogastric nerve (T12-L1)
(Location, motor and cutaneous innervation)
Location: passes in between the psoas major and quadratus lumborum muscle. Pierces a little bit the obliques (transversus abdominis muscle, internal and external oblique muscle)
- > The lateral branch goes to the lateral side of the body
- > The anterior branch curls all the way around the front and it ends superiorly to the inguinal canal
Cutaneous innervation: skin over the inguinal region (anterior branch) and upper lateral thigh (lateral branch)
Motor innervation: Lower internal obliques and transversus abdominis muscles
The Lumbar Plexus (L1-L4)
Describe the Ilioinguinal nerve (L1)
(Location, motor and cutaneous innervation)
Location: passes in between the psoas major and quadratus luborum muscles and pierces through the transversus abdominis muscle.
Travels between the transversus abdominis and internal oblique muscles within the inguinal canal
Motor innervation: Lower internal obliques and transversus abdominis muscles
Cutaneous innervation: skin over the anteromedial thigh, scrotal/labial branches
The Lumbar Plexus (L1-L4)
Describe the Genitofemoral nerve (L1-L2)
(Location, motor and cutaneous innervation)
Location: The genitofemoral nerve pierces through the psoas major muscle. It then splits into the Femoral branch (more lateral) and the Genital branch (more medial)
Femoral branch: pierces through the obliques muscles, travels under inguinal ligament to enter the thigh
Genital branch: pierces through the transversus abdominis muscle, travels within the inguinal canal
Cutaneous innervation:
- > Femoral branch: skin of the anterosuperior thigh
- > Genital branch: Shares some medial thigh innervation with the ilioinguinal branches
Motor innervation: provides innervation to the cremaster muscle on the spermatic cord. Allows the muscle of the testicules to contract and elevate
The Lumbar Plexus (L1-L4)
Describe the Lateral Femoral Cutaneous nerve of the thigh (TL2-L3)
(Location, cutaneous innervation)
Location: travels posterior to the psoas major muscle and on top of the iliacus muscle (iliac crest), pierces through the obliques and travelling underneath the inguinal ligament in the muscular compartment and into the lateral aspect of the thigh
Cutaneous innervation: Lateral side of the thigh
The Lumbar Plexus (L1-L4)
Describe the Obturator nerve (L2-L4)
(Location, motor and cutaneous innervation)
Location: Travels along the body of the ilium and it is going to exit the pelvis through the obturator foramen and branch into the anterior and posterior branch
Motor innervation: medial compartment of the thigh (adductors) Exception: secondary innervation to the pectineus muscle
Cutaneous innervation: skin of the medial thigh
The Lumbar Plexus (L1-L4)
Describe the Femoral nerve (L2-L4)
(Location, motor and cutaneous innervation)
Location: peeking out in between the psoas major and the iliacus muscle, travels deep underneath the inguinal ligament and enters in the thigh
Motor innervation: anterior compartment of the thigh (flexors of the hip, extensors of the knee), including pectineus from the medial compartment of the thigh
Cutaneous innervation: anterior thigh and medial leg/foot
The femoral nerve gives 2 cutaneous branches
- > Anterior femoral cutaneous nerve
- > Saphenous nerve:
Location: travels with the great saphenous vein along the medial thigh
The Sacral Plexus (L5-S4)
Describe the Superior and Inferior gluteal nerve
(Location, motor innervation)
Superior gluteal nerve (L4-S1)
Location: exits via the greater sciatic foramen (above piriformis)
Motor innervation: To the abductors of the thigh at the hip (gluteus medius, gluteus minimus, tensor fascia lata)
Inferior gluteal nerve (L5-S2)
Location: exits via the greater sciatic foramen (below piriformis)
Motor innervation: gluteus maximus
The Sacral Plexus (L5-S4)
Describe the Posterior femoral cutaneous nerve (S1-S3)
(cutaneous innervation)
Cutaneous innervation: innervation to the posterior thigh
The Sacral Plexus (L5-S4)
Describe the Sciatic nerve (L4-S3)
(Location, motor and cutaneous innervation)
Location: exits below piriformis (normal), one branch exits above and one below piriformis, one branch pierces piriformis and the other exits below the piriformis
Motor innervation: posterior compartment of the thigh, divisions of sciatic (at the popliteal fossa) extend down into the leg and foot
Sensory innervation: the sensory innervation is given by the tibial (L5-S3) and common fibular nerve (L4-S2). They give cutaneous innervation to the posterior and lateral leg and foot
The Sacral Plexus (L5-S4)
Describe the Pudendal nerve (S2-S4)
(Location, motor and cutaneous innervation)
Location: exits via greater sciatic foramen, enter through lesser sciatic foramen targeting the perineum (external genitalia)
comparing the dermatomes and cutaneous maps
