Somatic Nerves (Exam 2)

Borders of posterior triangle of neck; what nerve/nerve group is in this triangle

sternocleidomastoid (closer to ear), trapezius (posterior), scalene muscles (floor)

phrenic nerve; brachial plexus

Mnemonic for brachial plexus

Robert (Roots) - C5, C6, C7, C8, T1

Taylor (Trunks) - upper, middle, lower

Drinks (Divisions) - anterior (flexors), posterior (extensors)

Cold (Cords) - lateral (upper trunk), posterior (middle trunk), medial (lower trunk)

Beverages (Branches) - Dorsal Scapular Nerve (up, C5), Suprascapular (up, C5-C6) Musculocutaneous (lat. cord, C5-C7), Long Thoracic Nerve (up, C5-C7)

Median Nerve (post, C6-T1), Radial Nerve (post, C5-T1), Thoracodorsal (post, C6-C8), Axillary (post, C5-C6)

Ulnar nerve (med. cord, C8-T1)

Branches of brachial plexus (9)

Upper trunk = 4

• Dorsal Scapular Nerve (root, C5) - rhomboids, levator scapulae

• Suprascapular (trunk, C5-C6) - supra/infraspinatus

• Long Thoracic Nerve (root, C5-C7) - Serratus Anterior (protract scapula)

• Musculocutaneous (lat. cord, C5-C7) - biceps brachii, brachialis, coracobrachialis

Middle Trunk = 4 (all post cord)

• Thoracodorsal nerve (C6-C8) - latissimus dorsi (adduct/depress shoulder)

• Axillary Nerve (C5, C6) - deltoid, teres major

• Radial Nerve (C5-T1) - posterior muscles of arm/forearm

• Median Nerve (C6-T1) - Flexor muscles (except FCU)

  • Recurrent branch innervates intrinsic muscles of hand (Flexor pollicis brevis, Abductor pollicis brevis, Opponens pollicis (lat.))

Lower trunk = 1

• Ulnar nerve (C8, T1) - (deep branch) intrinsic muscles of the hand, FCU, half FDP

Know dermatomes we learned

C5 = shoulder, C6 = thumb, C7 = middle finger, C8 = thumb, T1 = medial elbow, T4 = nipple, T10 = bully button, L1 = inguinal ligament , L4 = medial Malleous, L5 = dorsal foot, S1 = heel

Know myotomes we learned

C5 = shoulder abduction, C6 = elbow flexion, C7 = elbow extension, C8 = wrist flexion, T1 = finger abduction, L2 = hip flexion, L3 = hip adduction, L4 = knee extension, L5 = dorsiflexion, S1 = plantarflexion

medial/lateral cutaneous nerves of ARM arise from

medial cutaneous = medial cord

lateral cutaneous = radial nerve

musculocutaneous → lateral cutaneous nerve of forearm

what nerve innervates deep forearm muscles; what/where is cubital fossa

median nerve (anterior interosseous nerve)→ FDP, FPL, pronator quadratus (between radius and ulna above wrist)

Cubital Fossa = TAN from lateral to medial (tendon of biceps, brachial artery, median nerve)

4 muscle stretch reflexes (buy three knee-d angels)

1. Biceps = C5, C6 (predominantly C5 - musculocutaneous) - inner elbow hit

2. Triceps = C7, C8 (predominantly C7- radial) - above post. elbow

3. Knee jerk = L2-L4 (predominantly L4 - femoral) - below patella

4. Ankle jerk = S1 (tibial) - Achilles

5. Brachioradiolis = C5, C6 (radial) - wrist

Median nerve branches into what nerve for thumb

Recurrent branch innervates intrinsic muscles of hand -

• Flexor pollicis brevis (medial)

• Abductor pollicis brevis (middle)

• Opponens pollicis (lat.)

• 2 lateral lumbricals

what to know about radial nerve

innerveates triceps, brachioradialis, and extensor carpi radialis then splits → superficial branch (dorsal hand) and posterior interosseus nerve (extensors)

peripheral nerves innervate what parts of skin?

1. Axillary - lower shoulder area

2. Radial - back of arm and lateral dorsal half of hand

3. Lateral antebrachialcutaneous (from musculocutaneous) - lateral elbow up to wrist

4. Medial antebrachial cutaneous - medial elbow+ up to wrist

5. Median - lateral (palmar) half of hand

6. Ulnar - medial (palmar and dorsal) half of hand

Where does lumbosacral plexus originate

Lumbar plexus - L1-L4; main branches → anterior thigh ; smaller branches → psoas and abdominal wall (motor); sensory - genitals/thigh

• lateral femoral cutaneous (L2,L3)

• femoral (lateral to psoas muscle)

• obturator (medial to psoas muscle)

• genitofemoral (on top of psoas muscle)

Sacral plexus - L4-S4

• sciatic nerve (anterior rami L4-S3)- leaves greater sciatic foramen

what is femoral triangle? where is safest place for glute injection?

between sartorius, adductor longus (medial), and inguinal ligament (top); upper outer quadrant

what root levels is the two leg nerves? area behind knee joint is called?

tibial = L4-S3; common fibular = L4-S2

popliteal fossa

what’s behind medial malleolus

TOM DICK AND NOW HARRY

Tibialis posterior, Flexor Digitorum Longus, post. tib artery, tibial nerve, Flexor Hallicus Longus

what are branches of tibial nerve

medial and lateral plantar nerves

Medial = LAFF

• lumbrical (first)

• abductor hallucis

• flexor digitorum brevis

• flexor hallucis brevis

Foot sensory innervations

• Saphenous = medial

• Sural = lateral

• Deep fibular = “great web” between 1st and second toe

• Superficial fibular = rest of dorsal foot