Exam 3: Sacral Nerves, Sacral Plexus, Coccygeal Plexus Flashcards
How many pairs of sacral spinal nerves are there?
5 pairs
Where do the sacral nerves descend inside and what do they help form?
descend inside the dura and form much of the cauda equina
How does each sacral nerve divide?
into an anterior primary ramus and a posterior primary ramus
What rami travel through the posterior sacral foramina?
posterior primary rami of S1-S4
Where does the S5 posterior ramus travel through?
the sacral hiatus
Describe the size of the posterior primary rami of the sacral nerves?
they decrease in size from superior to inferior
What rami of sacral nerves will divide?
the posterior primary rami of S1-S3 divide into medial and lateral branches
What do the medial branches and lateral branches of the posterior primary rami of S1-S3 supply?
Medial–> adjacent multifidi (motor)
Lateral–> combine with branches from L5 and S4 to supply skin over buttocks
What does the lateral branch of the posterior primary rami of S1-S3 combine with to supply?
combine with branches from L5 and S4 to supply skin over buttocks
What do the posterior primary rami of S4 and S5 do?
unit with coccygeal posterior rami to supply the skin over the coccyx
Where do the anterior primary rami of S1-S4 travel through? What about the anterior primary rami of S5?
the four anterior sacral foramina
S5 through sacral hiatus
What rami are traveling through the sacral hiatus?
posterior primary rami and the anterior primary rami of S5
What plexus do the anterior primary rami of sacral nerves contribute to?
Sacral plexus (S1-S4) Coccygeal plexus (S4,S5)
What other part of the nervous system do the Sacral Spinal nerves have communication with? What part of the sacral nerves communicates with it?
the sympathetic trunk
anterior primary ramus of each sacral nerve will receive POSTganglionic sympathetic fibers via a gray ramus communicans
How may sacral sympathetic ganglia are there?
usually 3-4
What forms the Sacral Plexus?
anterior primary rami of L4, L5, S1, S2, S3…and part of S4
The contribution of L4 and L5 to the sacral plexus is via what?
via the lumbosacral trunk
What nerve fibers are in the lumosacral trunk?
L4 and L5
On top of what muscle does the Sacral Plexus form?
on the anterior surface of the piriformis muscle
What do the nerve roots that supply the sacral plexus divide into and when do they do this?
anterior and posterior divisions shortly after exiting their IVF/sacral foramen
What are all the branches off the anterior division of the sacral plexus?
- Nerve to the quadratus femoris and gemellus inferior (L4,L5,S1)
- Nerve to the obturator internus and gemellus superior (L5,S1,S2)
- Pudendal Nerve ( S2,S3,S4)
- ind. Muscular branches to levator ani and coccygeus muscles (S4)
–contribute to posterior cutaneous nerve of the thigh (S2,S3) and Sciatic Nerve via the Tibial Nerve (L4-S3)
What nerve fibers does the Nerve to the quadratus femoris and gemellus inferior contain? How does it leave the pelvis? What actions do these muscles contribute to?
L4, L5, S1 nerves of anterior division
leaves via Greater Sciatic Foramen
contribute to lateral rotation and adduction of the thigh
What fibers does the Nerve to the obturator internus and gemellus superior carry? How do they leave the pelvis and give off the branches to the muscles?
L5, S1, S2 nerves of anterior division
via Greater Sciatic Foramen –> gives branch to gemellus superior, then–> RE-ENTERS pelvis via Lesser Sciatic Foramen to supply obturator internus
What action do the muscles of Nerve to the obturator internus and gemellus superior contribute to?
lateral rotation and abduction of the thigh
What nerve fibers does the Pudendal nerve contain? How does it leave the pelvis and can you describe its path?
S2, S3, S4 of anterior division
via Greater Sciatic Foramen–> arches around ischial spine–> and into perineum via Lesser Sciatic Foramen –> then travels in Pudendal Canal (inf. to pubic symphysis to dorsal side of penis/clitoris)
After the Pudendal Nerve arches around the ischial spine and into perinuem via the Lesser Sciatic Foramen, where does it travel next?
through the Pudendal Canal, inferior to the pubic symphysis to reach the dorsal side of the penis (males) or clitoris (females)
What are the branches that come off the Pudendal Canal in the Pudendal Canal?
- Inferior Rectal Nerves ( S and M)
- Perineal Nerve (divides into Deep-motor and Superficial-sensory branches)
- Dorsal nerve of the penis (males) or clitrois (females) (S and M)–is terminal branch of pudendal nerve
What does the Inferior Rectal Nerves supply?
(branch of Pudendal Nerve)
Sensory–> skin around anus and inf. 2/3 of anal canal
Motor–> external anal sphincter (anal wink ;)
What does the Perineal Nerve do?
(branch of Pudendal nerve) will divide into Deep motor branch and superficial sensory branch
What does the deep branch of the Perineal Nerve supply?
Motor:
- External anal sphincter
- Bulbosponsiosus
- Ischiocavernosus
- Superficial transverse perineus
What does the superficial branch of the Perineal Nerve supply?
Sensory:
- Males–> posterior scrotum, urethral mucosa, and bulb of penis
- Females–> labium majus, external urethral orifice, and vestibule
What is the terminal branch of the Pudendal nerve? What type of fibers does it carry?
Dorsal Nerve of the Penis (males) or Dorsal Nerve of the Clitoris (females)
- motor and sensory
What does the Dorsal Nerve of the Penis/Clitoris supply?
(terminal branch of Pudendal Nerve) Motor: - Deep transverse perineus - Urethral sphincter muscles Sensory: - Males--> corpus cavernosum, glans penis, and skin covering penis - Females--> corpus cavernosum, clitoris
What do the individual Muscular Branches off the sacral plexus contain fibers from and what do they supply?
fibers from S4
Supply Muscles:
- levator ani
- coccygeus
We splanchnic nerves come off the sacral plexus and what do they supply?
Pelvic Splanchnic nerves; fibers from S2, S3, and S4)
What are all the branches off the posterior division of the sacral plexus?
- Nerve to the Piriformis (S1, S2)
2, Superior Gluteal Nerve (L4, L5, S1) - Inferior Gluteal Nerve (L5, S1, S2)
- Perforating Cutaneous Nerve ( S2, S3)
–contributes to Posterior Cutaneous Nerve of the Thigh (S1, S2) and Sciatic Nerve via Common Fibular Nerve (L4-S2)
What nerve fibers does the Nerve to the Piriformis Muscle contain?
(branch of posterior division)
S1 and S2
What fibers does the Superior Gluteal Nerve contain and how does it leave the pelvis? What does it divide into?
(branch of posterior divison)
L4, L5, and S1
via Greater Sciatic Foramen, SUPERIOR to piriformis and splits into—> superior and inferior branches
What do the superior branches of the Superior Gluteal Nerve supply? What do the Inferior branches supply?
Superior –> gluteus medius and minimus
Inferior–> gluteus medius and minimus AND tensor fascia lata
What fibers does the Inferior Gluteal Nerve contain? How does it leave the pelvis? What does it supply?
(branch of posterior division)
L5, S1, and S2
via Greater Sciatic Foramen, INFERIOR to piriformis
supplies gluteus maximus
What is the Perforating Cutaneous Nerve named for and what fibers does it contain? What does it supply? Are there any anomalies?
named b/c it travels THROUGH the sacrotuberous ligament
sensory–> lower medial aspect of buttocks
(may instead be formed by branch off pudendal nerve OR be absent)
What two nerves of the sacral plexus are formed by BOTH anterior and posterior divisions?
- Posterior Cutaneous nerve of the Thigh ( Ant. S2, S3 and Post. S1, S2)
- Sciatic Nerve (Tibial Nerve–Ant. L4-S3; and Common Fibular Nerve–Post. L4-S2)
How does the Posterior Cutaneous Nerve of the Thigh leave the pelvis? Describe its path and what is ultimately communicates with.
via the Greater Sciatic Foramen–> descends through the posterior thigh and inferior to the leg–> ultimately communicates with Sural Nerve
What does the Posterior Cutaneous Nerve of the Thigh Supply?
(Ant. Div. S2,S3 and Post Div. S1, S2)
skin on posterior and medial thigh
What is the largest nerve in the human body?
Sciatic nerve; ~ 2 cm in diameter
spinal cord is also ~2 cm–WOW
What makes up the Sciatic Nerve?
Tibial Nerve from Ant. Div. (L4-S3)
Common Fibular Nerve From Post. Div. (L4-S2)
How does the Sciatic Nerve leave the Pelvis?
both parts w/in a common sheath, through the Greater Sciatic Foramen, BELOW the piriformis muscle
How does the Sciatic Nerve travel after exiting the pelvis via the Greater Sciatic Nerve below the piriformis muscle?
continues inferiorly on POSTERIOR aspect of adductor magnus and ~ 2/3 way to the knee is splits into its Common Fibular Nerve and Tibial Nerve components
(point at which nerve divides is quite variable)
What fibers it the Common Fibular Nerve Composed of? Is it more laterally located or medially located?
L4-S2 of post. div.; more laterally located
What branches are given off from the Common Fibular Nerve in the thigh before it separates from the Tibial Nerve fibers?
branch to one muscle–> Biceps Femoris (short head)
Once the Common Fibular Nerve separates from the Tibial nerve, what path does it take?
goes around lateral aspect of fibula and on reach the antero-lateral aspect of the leg it gives off an articular branch to the knee joint
What are the branches that the Common Fibular Nerve gives off?
- while still with Tibial nerve fibers–> branch to Biceps femoris (short head)
- articular branch to knee joint
Lateral Aspect of Popliteal Fossa:
- Lateral Sural Cutaneous Nerve
- Fibular Communicating Branch
Divides into:
- Superficial Fibular Nerve
- Deep Fibular Nerve
What branches does the Common Fibular Nerve give off on the lateral aspect of the popliteal fossa? What do they supply?
- Lateral Sural Cutaneous Nerve–> skin on lateral aspect of leg
- Fibular Communicating Branch –> combines with Medial Sural Cutaneous Nerve (from Tibial Nerve) and forms Sural Nerve
What form the Sural Nerve?
- Fibular Communicating Branch off the Common Fibular Nerve
and the - Medial Sural Cutaneous Nerve from the Tibial Nerve
After the Common Fibular Nerve gives off its two branches on the lateral aspect of the popliteal fossa, when what does it do?
Divides into the Superficial Fibular Nerve and the Deep Fibular Nerve (both have S and M)
How does the Superficial Fibular Nerve travel?
(off Common Fibular Nerve)
- -travels inferior b/w fibularis longus and fibula –> down to dorsum of the foot and supplies two muscles–> then splits into:
- Medial Dorsal Cutaneous Nerve
- Intermediate Dorsal Cutaneous Nerve
What muscles does the Superficial Fibular Nerve supply? What action do they do?
- Fibularis Longus
- Fibularis Brevis
(lateral compartment of leg)
action: eversion (and some plantar flexion b/c tendons go post. to lateral malleolus)
What are the Medial Dorssal Cutaneous Nerve and the Intermediate Dorsal Cutaneous Nerve branches of? What do they supply?
splits from the Superficial Fibular Nerve (branch of Common fibular nerve)
Supply: skin over dorsum of foot, EXCEPT skin b/w first two digits
Describe the path of the Deep Fibular Nerve.
(branch from Common Fibular Nerve)
runs inferiorly along tibialis anterior –> reaches dorsum of foot–> supplies extensor muscles of foot and toes and sensory to skin b/w first two digits
What nerve supplies the skin b/w the first two digits of the toes?
Deep Fibular Nerve
What muscles does the Deep Fibular Nerve supply?
(branch off Common Fibular Nerve) Found in ant. compartment: 1. Tibialis Anterior 2. Extensor Digitorum longus 3. Extensor hallucis longus 4. Fibularis tertius ~action = dorsal flexion ----------------------------- On dorsum of foot: 5. Extensor digitorum brevis 6. Extensor halluces brevis
What sensory supply does the the terminal branch of the Deep Fibular Nerve have?
sensory to skin b/w first two toes
If someone has a Steppage Gait for Foot Drop, what nerve are we thinking is involved?
Deep Fibular Nerve
cannot dorsiflex the foot (cannot raise their toe up) and will come down on toe first b/c must lift leg up higher so avoid tripping
What fibers make up the Tibial Nerve? Is it more laterally or medially located?
L4-S3, more medially located and is considerably larger than the common fibular nerve
While the Tibial Nerve is still combined with the Common Fibular Nerve, what muscles does it supply?
- Biceps Femoris (long head)
- Semitendinosus
- Semimembranosus
- Adductor magnus
When the Tibial Nerve is in the popliteal fossa, what branches does it give off?
- articular branches to knee joint
- Muscular branches to 4 muscles
- Popliteal Branch–> Interosseous nerve of the leg
- Medial Sural Cutaneous Nerve (so form Sural Nerve)
What muschles do the branches of the Tibial nerve given off in the popliteal fossa supply?
- Popliteus
- Gastrocnemius (both heads)
- Soleus
- Plantaris
What does the popliteal branch of the tibial nerve give rise to?
travels inferior to give rise to Interosseous Nerve of the Leg
What is the path of the Interosseous Nerve of the Leg? What does it supply?
(branch of popliteal branch of tibial nerve)
continues inferior along posterior surface of interosseous membrane
Sensory info from:
- tibial periosteum
- ankle
- tibiofibular joints
Once the Tibial Nerve is in the leg, what branches does it give rise to?
- Muscular branches (supply 3 muscles)
2. Medial Calcaneal Branches (sensory)
What do the muscular branches that arise from the Tibial Nerve in the leg supply?
- Flexor digitorum longus
- Flexor hallucis longus
- Tibialis posterior
What does the Medial Calcaneal branches supply?
(branch of tibial nerve in the leg)
- skin over medial heel
After giving off its branches in the leg, what does the Tibial Nerve do next?
travels around MEDIAL malleolus to plantar surface of foot and divides into two terminal branches:
- medial plantar nerve
- lateral plantar nerve
What are the two terminal branches of the Tibial Nerve?
- Medial Plantar Nerve (M and S)
2. Lateral Plantar Nerve (M and S)
What does the Medial Planter Nerve send motor fibers to? What action do theses muscles contribute to?
- Abductor hallucis
- Flexor digitorum brevis
- Flexor hallucis brevis
~~ plantar flexion and inversion
(deep posterior compartment)
What muscles does the Medial Plantar Nerve supply?
- Abductor hallucis
- Flexor digitorum brevis
- Flexor hallucis brevis
What will the Medial Plantar Nerve divide into? What do these branches supply?
Common Plantar digital nerves
Motor: to 1st lumbrical
Sensory: via Proper Plantar Digital Nerves to skin b/w toes
What does the Lateral Plantar Nerve do?
(a terminal branch of Tibial nerve) motor and sensory Divides into: - Superficial Branch (sensory) - Deep Branch (motor)
What does the Superficial Branch of the Lateral Plantar Nerve supply?
skin around 5th digit
What does the Deep Branch of the Lateral Plantar Nerve supply?
(terminal branch of Tibial nerve)
- Adductor hallucis
- Flexor digiti minimi brevis
- Abductor digiti minimi
- Quadratus plantae
- Lateral Lumbricals (3)
- Interossei muscles
What nerve can we test by having the patient flex their toes against your resistance or have them stand on their tippy toes?
Tibial Nerve–>
What can we have the patient do to test the sciatic nerve?
Tibial Nerve–> stand on tippy toes/flex toes
Common Fibular Nerve –> take steps on heels
Superficial Fibular Nerve–> have them evert vs resistance
What nerve is involved in hammer toes? Describe what is occur at the joints.
Tibial Nerve
- DIP –> hyperextended
- IP –> hyperflexed
- PIP –> hyperextended
What would “claw foot” be associated with?
tibial nerve (but tough to identify, but similar to claw hand)
What forms the Coccygeal Plexus?
anterior rami of S4, S5, and Co1 nerves
The nerves of the coccygeal plexus combine and form what? What type of information does it carry?
gives rise to anococcygeal nerves
– carries sensory info from skin adjacent to the coccyx and anus
(anal winking ;)
