Sacral plexus Flashcards
(28 cards)
Where is the sacral plexus located?
posterior pelvic wall, anterior to piriformis muscles (pelvic surface of sacrum to greater trochanter of femur - L5-S1)
What does the sacral plexus supply?
skin and muscles of the pelvis + lower limb
What is the sacral plexus formed by?
anterior compartment of Sacral spinal nerves (S1-S4), receives contribution from L4, L5 lumbar roots (forms lumbosacral trunk - joins lumbar to sacral plexus as sacral roots emerge from spinal cord)
what are the main nerves in the sacral plexus?
- superior gluteal nerve
- inferior gluteal nerve
- sciatic nerve
- posterior femoral cutaneous
- pudendal nerve
where do the main nerves of the sacral plexus travel through?
descend down the posterior pelvic wall
what are the 2 main destinations of the sacral plexus?
- leave pelvis via greater foramen
2. remain in the pelvis
what happens to the sacral nerves which remain in the pelvis?
innervate the pelvic muscles, organs and perineum (between anus and scrotum (M) / vulva (F))
what happens to the nerves which leave the pelvis via the greater sciatic foramen (opening a back of pelvis)?
enters gluteal region (bottom) of lower limb, innervating structures there
superior gluteal nerve:
where does it leave pelvis?
where does it enter?
what are the accompanying nerves and arteries?
SGN leaves pelvis via greater sciatic foramen
enters gluteal region superiorly to piriformis muscle
accompanied by superior gluteal artery and vein
Superior gluteal nerve:
root, motor, sensory
Roots: L5, L5, S1
Motor: gluteus minimus, gluteal medius, tensor fascia latae
Sensory: none
inferior gluteal nerve:
where does it leave and enter?
leaves pelvis via greater sciatic foramen
enters gluteal region inferior to piriformis muscle
Inferior gluteal nerve:
Roots, motor, sensory
Roots: L5, S1, S2
Motor: gluteus maximus
Sensory: none
Sciatic nerve roots
Roots: L4, L5, S1, S2, S3
Sciatic nerve motor innervation (tibial portion)
TIBIAL portion: all muscles posterior thigh, hamstring portion of adductor magnus, posterior leg and all muscles of foot
posterior thigh exceptions: short head of biceps femoris
What are the 2 portions of the sciatic nerve motor innervation?
tibial and common fibular portion
sciatic nerve motor (common fibular portion)
short head of biceps femoris
muscles of anterior and lateral compartments of the leg
extensor digitorum brevis
sciatic nerve sensory (tibial + common fibular)
tibial portion: skin on posterolateral + medial surfaces of foot + sole of foot
common fibular portion: skin on anterolateral suface of leg + dorsal aspect of foot
posterior femoral cutaneous (of thigh)
where it leaves and enter from sacral plexus?
leaves pelvis via greater sciatic foramen, enter gluteal region inferior to piriformis muscle
descends deep into gluteus maximus, runs down back of thigh to knee
Posterior femoral cutaneous
Roots, motor, sensory
Roots: S1, S2, S3
Motor: none
Sensory: skin on posterior surface of thigh + leg + skin of perineum (pelvic floor)
Pudendal nerve
exit and insert?
leaves pelvis via greater sciatic foramen, re-enters via lesser sciatic foramen
moves anterosuperiorly along lateral wall of ischiorectal fossa, terminates by dividing into several branches
Pudendal nerve
roots, motor, sensory
Roots: S2, S3, S4
Motor: innervates skeletal muscles in perineum, external urethral sphincter, external anal sphincter, levator ani
Sensory: innervates penis + clitoris + most of skin of perineum
S2, S3, S4 keeps the poo off the floor!
perforating cutaneous nerve (minor branch of sacral plexus)
sensory: skin over inferior gluteal region
pelvic splanchnic nerve (minor branch of sacral plexus)
innervate abdominal viscera
Name other minor branches of the sacral plexus
nerve to piriformis
nerve to Obturator internus
Nerve to Quadrator femoris
