Spinal Nerve Plexuses

Question 1

Plexus: Cervical

Important nerves: Phrenic

Answer 1

Origin (from ventral rami)
• C1–C5
Body areas served
• Diaphragm; skin and muscles of shoulder and neck
Result of damage to plexus or its nerves
• Respiratory paralysis (and death if not treated promptly)

Question 2

Plexus: Brachial

Important nerves: Axillary

Answer 2

Origin (from ventral rami)
• C5–C8 and T1
Body areas served
• Deltoid muscle and skin of shoulder; muscles and skin of superior thorax
Result of damage to plexus or its nerves
• Paralysis and atrophy of deltoid muscle

Question 3

Plexus: Brachial

Important nerves: Radial

Answer 3

Origin (from ventral rami)
• C5–C8 and T1
Body areas served
• Triceps and extensor muscles of the forearm; skin of posterior upper limb
Result of damage to plexus or its nerves
• Wristdrop—inability to extend hand at wrist

Question 4

Plexus: Brachial

Important nerves: Median

Answer 4

Origin (from ventral rami)
• C5–C8 and T1
Body areas served
• Flexor muscles and skin of forearm and some muscles of hand
Result of damage to plexus or its nerves
• Decreased ability to flex and abduct hand and flex and abduct thumb and index finger—therefore, inability to pick up small objects

Question 5

Plexus: Brachial

Important nerves: Musculocutaneous

Answer 5

Origin (from ventral rami)
• C5–C8 and T1
Body areas served
• Flexor muscles of arm; skin of lateral forearm
Result of damage to plexus or its nerves
• Decreased ability to flex forearm at elbow

Question 6

Plexus: Brachial

Important nerves: Ulnar

Answer 6

Origin (from ventral rami)
• C5–C8 and T1
Body areas served
• Some flexor muscles of forearm; wrist and many hand muscles; skin of hand
Result of damage to plexus or its nerves
• Clawhand—inability to spread fingers apart

Question 7

Plexus: Lumbar

Important nerves: Femoral (including lateral and anterior cutaneous branches)

Answer 7

Origin (from ventral rami)
• L1–L4
Body areas served
• Lower abdomen, anterior and medial thigh muscles (hip flexors and knee extensors), and skin of anteromedial leg and thigh
Result of damage to plexus or its nerves
• Inability to extend leg and flex hip; loss of cutaneous sensation

Question 8

Plexus: Lumbar

Important nerves: Obturator

Answer 8

Origin (from ventral rami)
•  L1–L4
Body areas served
• Adductor muscles of medial thigh and small hip muscles; skin of medial thigh and hip joint
Result of damage to plexus or its nerves
• Inability to adduct thigh

Question 9

Plexus: Sacral
Important nerves: Sciatic (largest nerve in body; splits to common fibular and tibial nerves just above knee)
• Common fibular (superficial and deep branches)
• Tibial (including sural and plantar branches)

Answer 9

Origin (from ventral rami)
• L4–L5 and S1–S4
Body areas served
• Lower trunk and posterior surface of thigh (hip extensors and knee flexors)
• Lateral aspect of leg and foot
• Posterior aspect of leg and foot
Result of damage to plexus or its nerves
• Inability to extend hip and flex knee; sciatica
• Footdrop—inability to dorsiflex foot
• Inability to plantar flex and invert foot; shuffling gait

Question 10

Plexus: Sacral

Important nerves: Superior and inferior gluteal

Answer 10

Origin (from ventral rami)
• L4–L5 and S1–S4
Body areas served
• Gluteus muscles of hip
Result of damage to plexus or its nerves
• Inability to extend hip (maximus) or abduct and medially rotate thigh (medius)