Flashcards in Sacral plexus (dave's notes) Deck (17):
Describe the sacral plexus
The sacral plexus is a flat triangular formation on the front of piriformis from the lumbosacral trunk and the upper four sacral nerves. There are six branches ??before dividing, then three from anteriorly and three from posteriorly??
What nerve do nerve roots S1 and S2 create?
Nerve to piriformis. Twigs pass back into the muscle
What nerve do nerve roots S2 and S3 create?
The perforating cutaneous nerve which supplies skin over the lower medial side of the buttock
List the three groups of the sacral plexus
Six branches of the plexus, then branches of the anterior division of the anterior rami, and branches of the posterior division of the anterior rami
From which division does the inferior gluteal nerve arise?
The posterior division of the anterior rami
List the six nerves of the sacral plexus and their nerve roots
Nerve to piriformis S1 S2
The perforating cutaneous nerve S2,3
Posterior femoral cutaneous S2,3
Pelvic splanchnic S2,3,4
Perineal branch of S4 - S4
List the branches of the anterior division of the anterior rami, and their nerve roots
Nerve to quadratus femoris L4,5, S1
Nerve to obturator internus L5, S1
Tibial part of the sciatic nerve, all five divisions
List the branches of the posterior division of the anterior rami and their nerve roots
Superior gluteal nerve L4,5,S1
Inferior gluteal nerve L5, S1, S2
Common perineal (fibular part of sciatic) L4, L5, S1, S2
Describe the course of quadratus femoris
Runs down deep in contact with the bone to sink into quadratus femoris
Describe the course of the nerve to obturator internus
Passes below prifomis, curls around the base of the ischial spine and sinks into obturator internus, supplying the superior gemellus
Describe the course of the superior gluteal nerve
Passes back around the sciatic notch above piriformis between gluteus medius and maximus, supplying both
Describe the course of the inferior gluteal nerve
Passes back below piriformis and sinks into gluteus maximus
Describe the origin of the common perineal nerve
Formed from four posterior divisions, joins the tibial nerve in the pelvis forming the sciatic nerve
Describe the course of the posterior femoral cutaneous nerve
Runs down below piriformis on the sciatic nerve. Remains beneath the fascia and has a series of perforating branches supplying from the buttock to the mid calf
Describe the pelvic splanchnic nerve. What does it supply?
Sacral parasympathetic outflow with contributions to the iliohypogastric plexus. Motor to the bladder and sigmoid, descending colon and causes erection.
Describe the course and branches of the pudendal nerve.
Enters the pudendal canal being the nerve to the pelvic floor and perineum. Has inferior rectal, perineal and dorsal nerve branches.