Quiz 5: Sacral Plexus Flashcards
The sacral plexus is formed by what levels?
Anterior Primary Rami L4, L5, S1-S3 and part of S4.
The contributions from L4 and L5 are by way of what?
Lumbosacral Trunk
The sacral plexus forms on the anterior surface of what muscle?
Piriformis
The nerve roots that contribute to the sacral plexus divide into what divisions shortly after exiting their IVF/sacral foramen?
Anterior and Posterior divisions
What are the main nerves that branch off the anterior division of the sacral plexus?
- Nerve to the quadratus femoris and gemellus inferior
- Nerve to the obturator internus and gemellus superior
- Pudendal Nerve
- Muscular Branches
- Pelvic Splanchnic Nerves
The Nerve to the Quadratus femoris and gemellus inferior contains fibers from what levels?
L4, L5 and S1
Where does the Nerve to the Quadratus femoris and gemellus inferior leave the pelvis?
Through the greater sciatic foramen
What is the function of the Quadratus femoris and Gemellus inferior muscles?
Contribute to lateral rotation and adduction of the thigh
The Nerve to the Obturator Internus and gemellus Superior contains fibers from what levels?
L5, S1 and S2
Where does the Nerve to the Obturator Internus and Gemellus Superior leave the pelvis?
Through the greater sciatic foramen
What does the Nerve to the Obturator Internus and Gemellus Superior give off branches to after leaving the pelvis through the greater sciatic foramen?
Branches to the Gemellus Superior
Where does the Nerve to the Obturator Internus and Gemellus Superior travel to after giving off branches to Gemellus Superior?
It re-enters the pelvis via the lesser sciatic foramen to supply the obturator internus.
What is the function of the Obturator Internus and Gemellus Superior muscles?
Contribute to lateral rotation and abduction of the thigh
The Pudendal Nerve contains fibers from what levels?
S2, S3, and S4
Where does the Pudendal Nerve leave the pelvic cavity?
Through the greater sciatic foramen
Where does the Pudendal Nerve travel after exiting the pelvis?
It arches around the ischial spine and into the perineum via the lesser sciatic foramen
After travelling through the lesser sciatic foramen where does the pudendal nerve travel?
It travels in the Pudendal Canal, inferior to the pubic symphysis to reach the dorsal side of the penis or clitoris.
What are the branches of the Pudendal Nerve that exit within the Pudendal Canal?
- Inferior Rectal Nerves
- Perineal Nerve
- Dorsal Nerve of the Penis/Clitoris
Where do the inferior rectal nerves carry sensory information from?
Skin around the anus and the inferior 2/3 of the anal canal
Where do the inferior rectal nerves carry motor info?
External Anal Sphincter
What branches does the Perineal Nerve divide into?
Deep and Superficial Branches
Where do the deep branches of the Perineal Nerve carry motor info?
The following four muscles:
- External Anal Sphincter
- Bulbosponsiosus
- Ischiocavernosus
- Superficial Transverse Perineus
Where do the superficial branches of the Perineal Nerve carry sensory info from in males?
- Posterior scrotum
- Urethral mucosa
- Bulb of the Penis
Where do the superficial branches of the Perineal Nerve carry sensory info from in females?
- Labium majus
- External Urethral Oriface
- Vestibule
What is the terminal branch of the pudendal nerve?
Dorsal Nerve of the Penis/Clitoris
What muscles are supplied by the Dorsal Nerve of the Penis/Clitoris?
- Deep Transverse Perineus
2. Urethral Sphincter Muscles
Where does the Dorsal Nerve of the Penis/Clitoris carry sensory info from in males?
- Corpus Cavernosum
- Glans Penis
- Skin covering the penis
Where does the Dorsal Nerve of the Penis/Clitoris carry sensory info from in females?
- Corpus Cavernosum
- Clitoris
Individual Muscular Branches off the sacral plexus contains fibers from what levels?
S4 only
What muscles do the Muscular Branches supply?
Levator Ani & Coccygeus Muscles
The Pelvic Splanchnic Nerves contain fibers from what levels?
S2, S3 and S4
What are the main nerves that branch off the posterior division of the sacral plexus?
- Nerve to the Piriformis
- Superior Gluteal Nerve
- Inferior Gluteal Nerve
- Perforating Cutaneous Nerve
The nerve to the piriformis carries fibers from what levels?
S1 and S2
What muscle does the nerve to the piriformis supply?
Piriformis
The Superior Gluteal Nerve is made up of fibers from what levels?
L4, L5 and S1
Where does the Superior Gluteal Nerve leave the pelvis?
Greater Sciatic foramen, superior to the piriformis
What does the Superior Gluteal Nerve split into?
Superior and Inferior Branches
What muscles do the superior branches of the Superior Gluteal Nerve supply?
- Gluteus medius
2. Gluteus minimus
What muscles do the inferior branches of the Superior Gluteal Nerve supply?
- Gluteus medius
- Gluteus minimus
- Tensor Fascia Lata
The inferior gluteal nerve carries fibers from what levels?
L5, S1 and S2
Where does the Inferior Gluteal Nerve leave the pelvis?
Through the greater sciatic foramen, inferior to the piriformis
What muscle does the inferior gluteal nerve supply?
Gluteus Maximus
The Perforating Cutaneous Nerve contains fibers from what levels?
S2 and S3
Where does the Perforating Cutaneous Nerve travel?
Through the sacrotuberous ligament, ultimately reaching the lower medial aspects of the buttocks
What is unique about the perforating cutaneous nerve?
It may be formed by a branch off of the pudendal nerve or may be absent
What two nerves are formed by BOTH the anterior and posterior divisions of the sacral plexus?
- Posterior Cutaneous Nerve of the Thigh
2. Sciatic Nerve
The Posterior Cutaneous Nerve of the thigh is formed by fibers from what levels?
Anterior division: S2 & S3
Posterior division: S1 & S2
Where does the Posterior Cutaneous Nerve of the thigh leave the pelvis?
Through the greater sciatic foramen
Where does the Posterior Cutaneous Nerve of the thigh travel after exiting the pelvis?
It descends through the posterior thigh and inferior to the leg
What does the posterior cutaneous nerve of the thigh ultimately communicate with in the leg?
Sural Nerve
Where does the Posterior cutaneous nerve supply sensory info?
Posterior and medial thigh
What is the largest nerve in the human body?
Sciatic
How large is the diameter of the sciatic?
2cm
What is the sciatic nerve actually a combination of?
Tibial and Common Fibular Nerves
The sciatic nerve leaves the pelvis through what?
Through the greater sciatic foramen below the piriformis muscle
*With both parts of the sciatic nerve in a common sheath
Where does the sciatic nerve travel after leaving the greater sciatic foramen?
It travels inferior on the posterior aspect of the adductor magnus.
Approximately 2/3 of the way to the knee, the sciatic nerve will split into what?
Common Fibular and Tibial Components
Is the point at which the nerve divides typically consistent?
No, it is actually quite variable. It some cases it may travel further before dividing. In other cases, the two may be separate for their entire length.
The common fibular nerve is the (medial/lateral) branch of the sciatic?
Lateral
The tibial nerve is the (medial/lateral) branch of the sciatic.?
Medial
The common fibular nerve is composed of fibers from what levels?
L4-S2
What one muscle does the common fibular nerve give off branches to before separating from the tibial nerves?
Biceps femoris (short head)
After separating from the tibial nerve, the common fibular nerve travels where?
It courses around the lateral aspect of the fibula
Upon reaching the antero-lateral aspect of the leg, what branch does the common fibular nerve give off?
Articular branch to the knee joint
What two branches does the common fibular nerve give off as it travels along the lateral aspect of the popliteal fossa?
- Lateral sural cutaneous nerve
2. fibular communicating branch
What does the lateral sural cutaneous nerve supply?
Skin on the lateral aspect of the leg
What does the fibular communicating branch form?
It forms the sural nerve after combining with the medial sural cutaneous nerve
What does the common fibular nerve divide into?
- Superficial fibular nerve
2. Deep fibular nerve
Where does the superficial fibular nerve travel?
Inferior between the fibularis longus and the fibula down to the dorsum of the foot
What two muscles are supplied by the superficial fibular nerve?
- Fibularis Longus
2. Fibularis Brevis
What does the Superficial Fibular Nerve divide into?
- Medial Dorsal Cutaneous Nerve
2. Intermediate Dorsal Cutaneous Nerve
The Medial Dorsal Cutaneous Nerve and the Intermediate Dorsal Cutaneous Nerve combine to supply what?
Skin over the dorsum of the foot, minus the skin between the first two toes
Is the Deep Fibular Nerve (Cutaneous or Muscular) in nature?
Muscular
Where does the Deep Fibular Nerve travel?
It runs inferiorly along the tibialis anterior to reach the dorsum of the foot.
What musculature does the Deep Fibular Nerve supply?
Extensor muscles of the foot and toes including:
- Tibialis Anterior
- Extensor Digitorum Longus
- Extensor Digitorum Brevis
- Extensor Hallucis Longus
- Extensor Hallucis Brevis
- Fibularis Tertius
The terminal branch of the Deep Fibular Nerve is cutaneous and supplies what?
Skin between the first two toes
What is the clinical term for losing the ability to actively dorsiflex, therefore needing to actively pick up the foot higher when walking to prevent it from dragging on the ground?
Steppage Gait (Foot Drop)
The Tibial Nerve is made up of fibers from what levels?
L4-S3
Is the Tibial Nerve smaller or larger than the Common Fibular Nerve?
Considerably Larger
While still combined with the Common Fibular Nerve, Tibial Nerve fibers are sent to which muscles?
- Biceps Femoris (long head)
- Semitendonosus
- Semimembranosus
- Adductor Magnus
In the Popliteal Fossa, the Tibial Nerve gives off what?
Articular branches, Muscular branches & Popliteal Branch
The articular branches of the tibial nerve supply what (in the popliteal fossa)?
Knee joint
The muscular branches of the tibial nerve supply what (in the popliteal fossa)?
- Popliteus
- Gastrocnemius (ant. compartment of leg)
- Soleus (ant. compartment of leg)
- Plantaris
The popliteal branch of the tibial nerve travels where?
Inferior
The popliteal branch of the tibial nerve gives rise to what nerve?
Interosseous nerve of the leg
Where does the interosseous nerve of the leg travel?
Continues inferior along the posterior surface of the interosseous membrane
What does the interosseous nerve of the leg supply sensory info to?
Tibial periosteum, ankle, and tibiofibular joints
In the leg, the tibial nerve gives rise to what?
Muscular branches and Sensory branches
What do the muscular branches of the tibial nerve supply (in the leg)?
- Flexor Digitorum Longus
- Flexor Hallucis Longus
- Tibialis Posterior
*All in posterior compartment of the leg
What is the name for the sensory branches of the tibial nerve (in the leg)?
Medial Calcaneal Branches
What do the sensory branches of the tibial nerve supply (in the leg)?
Skin over the medial heel
The tibial nerve travels around the medial malleolus (through the tarsal tunnel) to where?
Plantar surface of the foot
What does the Tibial nerve divide into at the plantar surface of the foot?
Two terminal branches:
- Medial plantar nerve
- Lateral plantar nerve
The medial plantar nerve sends motor fibers to what?
- Abductor hallucis
- Flexor digitorum brevis
- Flexor hallucis brevis
What does the medial plantar nerve divide into?
Common Plantar Digitial Nerves
What do the common plantar digital nerves provide motor supply to?
Lumbricals 1 & 2
What do the common plantar digital nerves provide sensory supply to?
Skin between toes by way of Proper Plantar Digital Nerves
What does the lateral plantar nerve divide into?
- Superficial branch
2. Deep branch
What does the superficial branch of the lateral plantar nerve supply?
Skin around the 5th digit
What does the deep branch of the lateral plantar nerve supply?
Motor fibers to:
- Adductor hallucis
- Flexor digiti minimi brevis
- Abductor digiti minimi
- Quadratus plantae
- Lateral Lumbricals
- Interossei muscles
What clinical condition associated with the tibial nerve had damage that occurs proximal to tarsal tunnel syndrome?
Flexor Paralysis
What is the clinical condition that involves hyperextension of the MTP joint, flexion of the PIP joint and Extension of the DIP joint?
Hammer toes
Is claw foot common?
No
What is the clinical term for checking the reflex at the back of the ankle/heel?
Achilles’ Reflex