Exam 3: Sacral Plexus Flashcards by AJ Fairchild

Sacral plexus formed by

Anterior primary rami of L4, L5, S1-3 and part of S4

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L4 and L5 contributions are by way of

Lumbosacral trunk

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Sacral plexus forms anterior to

Piriformis muscle

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Nerve roots forming sacral plexus divide into

Anterior and posterior divisions

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Branches of the anterior divisions

N to obturator interior and superior gemellus
N to quadratus femoris and inferior gemellus
Pudendal N
To coccygeus and levator ani
Tibial N

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Nerves formed by posterior divisions

Superior gluteal
Inferior gluteal
N to piriformis
Perforating cutaneous N
Common fibular N

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N to quadratus femoris and gemellus inferior contains fibers from

L4, L5, S1

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N to quadratus femoris and gemellus inferior leaves pelvis through

Greater sciatic foramen

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Quadratus femoris and gemellus inferior contribute to

Lateral rotation and adduction of thigh

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N to obturator internus and gemellus superior contains fibers from

L5, S1, S2

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N to obturator internus and gemellus superior leaves pelvis through ___ and gives off branches to ____

Greater sciatic foramen; gemellus superior

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N to obturator internus and gemellus superior re-enters pelvis via ____ to supply ____

Lesser sciatic foramen; obturator internus

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Obturator internus and gemellus superior contribute to

Lateral rotation and abduction of thigh

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Pudendal N contains fibers from

S2, 3, 4

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Pudendal N leaves pelvic cavity through ___, arches around ischial spine and into perineum via ____

Greater sciatic foramen; lesser sciatic foramen

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Pudendal N travels in the ____, to reach dorsal side of _____/____

Pudendal canal; penis/clitoris

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Branches off of pudendal N in pudendal canal

Inferior rectal N
Perineal N
Dorsal N of penis/clitoris

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Inferior rectal N carries sensory info from

Skin around anus

Inferior 2/3 of anal canal

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Inferior rectal nerves motor supply to

External anal sphincter

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Perineal N divides into

Deep and superficial branches

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Deep branches of pudendal N supply

External anal sphincter
Bulbospongiosus
Ischiocavernosus
Superficial transverse perineus

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Superficial branches of pudendal N supply in males

posterior scrotum
urethral musoca
bulb of penis

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Superficial branches of pudendal N supply in females

Labium majus
External urethral orifice
Vestibule

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Terminal branch of pudendal N

Dorsal nerve of penis/clitoris

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Dorsal N of penis/clitoris motor supply

Deep transverse perineus | Urethral sphincter muscles

Dorsal N of penis sensory supply in males

Corpus cavernosum Glans penis Skin covering penis

Dorsal N of clitoris sensory supply in females

Corpus cavernosum | Clitoris

Muscular branches containing fibers from S4 supply

Levator ani | Coccygeus

N to piriformis carries fibers from ____ to supply ____

S1 and S2 Piriformis

Superior gluteal N is made up of fibers from

L4, L5, S1

Superior gluteal N leaves pelvis through greater sciatic foramen, superior to ____ and splits into

Piriformis; superior and inferior branches

Superior branches of superior gluteal N supply

Gluteus medius and minimus

Inferior branches of superior gluteal N supply

Gluteus medius, minimis and tensor fascia lata

Inferior gluteal N carries fibers from

L5, S1, S2

Inferior gluteal N leaves pelvis through grater sciatic foramen, inferior to ___ and innervates ____

Piriformis; gluteus maximus

The perforating cutaneous N contains fibers from

S2 and S3

Perforating cutaneous N travels through ___, ultimately reaching ___

Sacrotuberous lig Lower medial buttocks

Nerves formed by both anterior and posterior divisions of sacral plexus

Posterior cutaneous N of thigh | Sciatic N

Posterior cutaneous N of thigh formed by fibers from anterior divisions of ____ and posterior divisions of ____

S2 and S3 S1 and S2

Largest N in human body

Sciatic N

Sciatic N is a combination of two nerves

Tibial N medially | Common fibular N laterally

Tibial N formed from anterior divisions of

L4-S3

Common fibular N formed from posterior divisions of

L4-S2

Sciatic N leaves pelvis through sciatic foramen, below

Piriformis muscle

Sciatic N travels inferior on posterior aspect of

Adductor magnus

2/3 of way down to knee sciatic N

Splits into common fibular and tibial N

Common fibular gives off one branch to ___ in the thigh

Biceps femoris (short head)

Common fibular N courses around ____ and gives off articular branch to ____

Lateral aspect of fibula; knee

2 sensory branches given off along lateral aspect of popliteal fossa

Lateral sural cutaneous N | Fibular communicating branch

Lateral sural cutaneous N supplies

Skin on lateral aspect of leg

Fibular communicating branch forms sural N after combining w/

Medial sural cutaneous N

Common fibular N divides into

Superficial and deep fibular N

Superficial fibular N travels inferior btw _____ down to dorsum of foot

Fibularis longus and fibula

Superficial fibular N supplies these muscles in lateral compartment of leg

Fibularis longus | Fibularis brevis

Superficial fibular N splits into ________ in the foot

Medial and intermediate dorsal cutaneous N

Medial and intermediate dorsal cutaneous nerves supply

Skin over dorsum of foot EXCEPT for between first two toes

Deep fibular N runs inferiorly along ___ to reach dorsum of foot

Tibialis anterior

Deep fibular N supplies these muscles

Tibialis anterior Extensor digitorum longus/brevis Extensor hallicis longus/brevis Fibularis tertius

Deep fibular N terminal branch supplies

Skin btw first two toes

Steppage gait (foot drop)

Unable to lift big toe | Foot slap

While tibial N is still combined w/ common fibular N, branches are sent to

Biceps femoris (long head) Senitendinosus Semimembranosus Adductor magnus

In popliteal fossa, tibial N gives off articular branches to

Knee

In popliteal fossa, tibial N gives off muscular branches to

Popliteus Gastrocnemius Soleus Plantaris

Tibial N supplies muscles that are in ____ compartment

Superficial posterior

The popliteal branch travels inferior to give rise to

Interosseous N of leg

Interosseous N of leg continues inferior along

Posterior surface of interosseous membrane

Interosseous N of leg carries sensory info from

Tibial periosteum Ankle Tibiofibular joints

The tibial nerve gives rise to _______ branches in the leg that supply:

Muscular 1. Flexor digitorum longus 2. Flexor hallucis longus 3. Tibialis posterior

Sensory branches of the tibial nerve in the leg are called _____ and supply skin _______

Medial Calcaneal branches Skin over the medial heel

Before branching into it’s terminal branches, the tibial nerve travels

Around the medial malleolus to the plantar surface of the foot

Terminal branches of tibial nerve

Medial plantar nerve and lateral plantar nerve

Medial plantar nerve sends _____ fibers to:

Motor - ABductor hallucis - Flexor digitorum brevis - Flexor hallucis brevis

Medial plantar nerve divides into

Common plantar digital nerves

Common plantar digital nerves supply

* Motor supply to 1st lumbrical | - Sensory to skin between toes via proper plantar digital nerves

Lateral plantar nerve divides into

Superficial (sensory) and deep (motor) branches

Superficial branch of lateral plantar nerve supplies

Skin around the 5th digit

Deep branch of lateral plantar nerve supplies

1. ADductor hallucis 2. Flexor digiti minimi brevis 3. ABductor digiti minimi 4. Quadratus plantae 5. Lateral lumbricals (2,3,4) 6. All interossei muscles

Flexor paralysis

Indicates damage to tibial nerve

Hammer toes

Chronic overactivity of tibial nerve. Tendons for the toe flexors shorten

Coccygeal plexus if formed by

Anterior rami of S4, S5, and Co1

Coccygeal plexus gives rise to _______ nerves that carry sensory information to:

Anococcygeal nerves Sensory info from skin adjacent tot coccyx and anus