Sacral And Coccygeal Plexuses Flashcards
Through which opening do the posterior primary rami of S1-S4 travel through?
The four posterior sacral foramina
Through which opening does the S5 posterior ramus travel through?
Sacral hiatus
In which direction do the sacral posterior rami decrease in size?
From superior to inferior
Which of the sacral posterior primary rami divide into medial and lateral branches?
S1-S3
What do the medial branches of S1-S3 posterior primary rami supply?
Adjacent multifidi
What do the lateral branches of the posterior primary rami of S1-S3 supply?
Skin over the buttocks (combined with branches from L5 and S4)
What is the supply of the posterior primary rami of S4 and S5 and their union with the coccygeal posterior rami?
Skin over the coccyx
What travels through the anterior sacral foramina?
Anterior primary rami of S1-S4
Which sacral anterior primary ramus travels through the sacral hiatus?
S5
There are usually how many sacral sympathetic ganglia that form the communication with the sympathetic trunk?
Three or four
The anterior primary ramus of each sacral nerve will receive what kind of information via a gray ramus communicans?
Postganglionic sympathetic fibers
What forms the sacral plexus?
Anterior primary rami of L4, L5, S1-S3, part of S4
What forms the lumbosacral trunk?
L4 and L5
The sacral plexus forms on the anterior surface of what muscle?
Piriformis
When do the nerve roots of the sacral plexus divide into anterior and posterior divisions?
Shortly after exiting their IVF/sacral foramen
What fibers are contained in the nerve to the quadratus femoris and gemellus inferior?
L4, L5, and S1
The nerve to the quadratus femoris and gemellus inferior leaves the pelvis through what opening?
Greater sciatic foramen
The muscles supplied by the nerve to the quadratus femoris and gemellus inferior share what common action?
Lateral rotation and adduction of the thigh
What fibers are contained in the nerve to the obturator internus and gemellus superior?
L5, S1, S2
The nerve to the obturator internus and gemellus superior leaves the pelvis through what opening?
Greater sciatic foramen
The nerve to the obturator internus and gemellus superior re-enters the pelvis through what opening to supply what muscle?
Lesser sciatic foramen, obturator internus
The muscles that are supplied by the nerve to the obturator internus and gemellus superior share what common action?
Lateral rotation and abduction of the thigh
What fibers are contained in the pudendal nerve?
S2, S3, and S4
What is the course of the pudendal nerve?
Leaves pelvic cavity through greater sciatic foramen, arches around the ischial spine and into the perineum via lesser sciatic foramen
Then, through the pudendal canal inferior to the pubic symphysis to reach dorsal side of penis or clitoris
What branches of the pudendal nerve come off within the pudendal canal?
Inferior rectal nerves, perineal nerve, dorsal nerve of penis/clitoris
The superior and inferior gluteal nerves are named in reference to what muscle?
Piriformis
The inferior rectal nerves carry sensory information from what locations?
Skin around the anus and the inferior 2/3 of the anal canal
What is the motor supply of the inferior rectal nerves?
External anal sphincter
Which branch of the perineal nerve has motor supply? Which has sensory supply?
Motor - deep branch
Sensory - superficial branch
What muscles are supplied by the deep branches of the perineal nerve?
External anal sphincter, bulbospongiosus, ischiocavernosus, superficial transverse perineus
What do the superficial branches of the perineal nerve supply?
Males - posterior scrotum, urethral mucosa, bulb of penis
Females - labium majus, external urethral orifice, and vestibule
What muscles are supplied by the dorsal nerve of the penis/clitoris?
Deep transverse perineus, urethral sphincter muscles
The dorsal nerve of the penis/clitoris carries sensory fibers from what location?
Males - corpus cavernosum, glans penis, skin covering penis
Females - corpus cavernosum, clitoris
What supplies the levator ani and coccygeus muscles?
Individual muscular branches off the sacral plexus in fibers from S4
The pelvic splanchnic nerves contain fibers from what nerves?
S2, S3, and S4
What are the branches from the posterior division of the sacral plexus?
Nerve to piriformis, superior and inferior gluteal nerves, perforating cutaneous nerve
What fibers are contained in the nerve to the piriformis?
S1 and S2
The sacral spinal nerves descend inside the dura to form what structure?
Much of the cauda equina
How can one test for damage to the obturator nerve by analyzing muscle weakness?
See if patient can adduct hip and if weak on one side, obturator nerve is likely to be compromised.
(if bilateral, more of a systemic issue)
How many gray rami communicans can be seen among the sacral spinal nerves?
5 (one for each)
What fibers are contained in the superior gluteal nerve?
L4, L5, and S1
What is the course of the superior gluteal nerve?
Leaves pelvis through greater sciatic foramen, superior to the piriformis, and splits into superior and inferior branches
Which muscles are supplied by the superior branches of the superior gluteal nerve?
Gluteus medius and minimus
What muscles are supplied by the inferior branches of the superior gluteal nerve?
Gluteus medius, minimus, and tensor fascia lata
What fibers are contained in the inferior gluteal nerve?
L5, S1, and S2
What is the course of the inferior gluteal nerve?
Leaves pelvis through greater sciatic foramen, inferior to piriformis, innervates gluteus maximus