Sacral Plexus Flashcards
What is the sacral plexus?
A network of nerve fibres that supplies the skin and muscles of the pelvis and lower limb
Where is the sacral plexus located?
On the surface of the posterior pelvic wall, anterior to the piriformis muscle
What is the sacral plexus formed by?
The anterior rami (divisons) of the sacral spinal nerves S1, S2, S3, and S4.
It also receives contributions from the lumbar spinal nerves L4 and L5
Where does the sacral plexus begin?
As the anterior fibres of S1, S2, S3, and S4
What forms the lumbosacral trunk?
The 4th and 5th lumbar roots
What happens to the lumbosacral trunk?
It descends into the pelvis, to meet the sacral roots as they emerge from the spinal cord
What happens to the anterior rami of the S1-S4 spinal roots and the lumbosacral trunk?
They divide into several cords, which then combine together to form the five major peripheral nerves of the sacral plexus
Where do the give major peripheral nerves of the sacral plexus travel?
They descent down the posterior pelvic wall, and then either-
Leave the pelvis via the greater sciatic foramen
Remain in the pelvis
What happens to the nerves that leave the pelvis via the greater sciatic foramen?
They enter the gluteal region of the lower limb, innervating the structures there
What happens to the nerves that remain in the pelvis?
They innervate the pelvic muscles, organs and perineum
What are the five major peripheral nerves of the brachial plexus?
Superior gluteal nerve Inferior gluteal nerve Sciatic nerve Posterior femoral cutaneous Pudendal
What course does the superior gluteal nerve take?
It leaves the pelvis via the greater sciatic foramen, entering the gluteal region superiorly to the piriformis muscle
What is the superior gluteal muscle accompanied by for much of its course?
The superior gluteal artery and vein
What are the roots of the superior gluteal nerve?
L4, L5, S1
What muscles does the superior gluteal nerve innervate?
Gluteus minimis
Gluteus medius
Tensor fascia latae
What are the sensory functions of the superior gluteal nerve?
None
What course does the inferior gluteal nerve take?
It leaves the pelvis via the greaer sciatic foramen, entering the gluteal region inferiorly to the piriformis muscle
What is the inferior gluteal nerve accompanied by for much of its course?
The inferior gluteal artery and vein
What are the roots of the inferior gluteal nerve?
L5, S1, S2
What muscle does the inferior gluteal nerve innervate?
Gluteus maximus
What is the sensory function of the inferior gluteal nerve?
None
What are the roots of the sciatic nerve?
L4, L5, S1, S2, S3
What are the parts of the sciatic nerve?
Tibial portion
Common fibular portion
What muscles does the tibial portion of the sciatic nerve innervate?
All muscles of posterior compartment of thigh, including the hamstring portion of the adductor magnus, apart from the short head of the biceps femoris
All muscles in the posterior compartment of the leg
All muscles in sole of foot
