EXAM2_Brachial_Plexus_G10G11

Question 1

What are the roots of the brachial plexus?

Answer 1

Anterior spinal roots (purely motor) and posterior spinal roots (purely sensory) merge into a spinal nerve (both sensory and motor). These spinal nerves split into the anterior primary root (limbs/body wall) and the posterior primary root (intrinsic back muscles).

The brachial plexus roots are the nerves from the Anterior Primary Rami of spinal nerves C5 to T1

C5 ROOT FORMS DORSAL SCAPULAR NERVE

the Roots C5-C6 form a Superior Trunk
The roots C7 form a middle Trunk
The roots C8-T1 form an Inferior Trunk

Question 2

Trunks of the Brachial plexus

Answer 2

Superior Trunk (C5, C6 Roots): Forms:

• SUPRASCAPULAR NERVE
• NERVE to SUBCLAVIUS

Middle Trunk (C7 Roots)
Inferior Trunk (C8, T1 Roots)

Each Trunk DIVIDES into an
Anterior Division and a Posterior Division

Question 3

DIVISIONS of the Brachial Plexus

The divisions of what trunks forms the Lateral, Posterior, Middle Cords?

Answer 3

Each Trunk divides into an Anterior and a posterior Division
No other nerves come off at these divisions

Anterior divisions of Superior & middle trunk= Lateral Cord
Posterior divisions of all trunks forms= Posterior Cord
Anterior divisions of Inferior Trunk forms= Medial Cord

Question 4

CORDS of the Brachial Plexus:
LATERAL CORD
What formed by?

1 Nerve?

1 Structure contributes C5,6,7 to MEDIAN NERVE?

Answer 4

LATERAL CORD:
– formed by anterior divisions of Superior & middle Trunk

• LATERAL PECTORAL NERVE
• Lateral root of lateral cord and medial root of medial cord forms the Median nerve

Question 5

CORDS of the Brachial Plexus:

POSTERIOR CORD

2 Terminal branches?
3 Nerves?

Answer 5

POSTERIOR CORD:
– Formed by Posterior divisions of all trunks

• Forms AXILLARY NERVE (C5, C6)
• Forms RADIAL NERVE (C5,6, 7, 8, T1)
• Forms SUBSCAPULAR NERVES :
• – Upper (C5,C6)
• –Middle (THORACODORSAL) (C6,7,8)
• –Lower (C5,6)

Question 6

CORDS of the Brachial Plexus:

MEDIAL CORD:
What formed by?

1 Terminal Branch, 3 Nerves

1 Structure contributes to C8 & T1 to MEDIAN nerve

Answer 6

MEDIAL CORD:
-formed by anterior divisions of Inferior Trunk

• Median Root forms MEDIAN NERVE (C5,6,7,8,T1)
• Forms ULNAR NERVE
• MEDIAL PECTORAL NERVE
• MEDIAL BRACHIAL CUTANEOUS NERVE
• MEDIAL ANTEBRACHIAL CUTANEOUS NERVE

Question 7

TERMINAL BRANCHES of the Brachial plexus

Answer 7

Each Cord divides into two terminal branches (5 total)

Musculocutaneous (Biceps, Coracobrachialis, Brachialis)
Axillary (Teres Minor & Deltoid)
Radial (All extensors & brachioradialis)
Median (1/2 LOAF) of hand & Flexors of Forearm (except medial head of flexor digitorum profundus)

Ulnar (The rest of Anterior arm/forearm/hand muscles)

Question 8

Axillary Nerve
What Spinal root contributions (SRC)? 
Cord? 
Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 8

Axillary Nerve

• (C5, C6)
• From Posterior Cord
• Deltoid (Ant: Flexion, Med rotation; Mid: ABduction; Post: Extension, Lateral Rotation)- of Humerus
• Teres Minor (Lateral Rotation)- of Humerus

Question 9

Musculocutaneous Nerve
What Spinal root contributions (SRC)? 
Cord? 
Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 9

Musculocutaneous
(C5, C6, C7)
-from Lateral Cord (superior & middle Trunk)
-Biceps Brachii (Flex Forearm- weak arm)
-Coracobrachialis (Flex Arm- resist dislocation)
-Brachialis (Flex Forearm- weak arm)

Question 10

Lateral Pectoral Nerve
What Spinal root contributions (SRC)? 
Cord? 
Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 10

Lateral Pectoral Nerve
(C5,C6, C7)
-From Lateral Cord (superior & middle trunk)
-Pectoralis Major (Adduction, Medial Rotation of Arm)
-

Question 11

Lateral Root of Lateral Cord

What spinal levels does it contribute to the MEDIAN NERVE?

If lesioned What 4 muscles affected?

Answer 11

Lateral Root of Lateral Cord

Contributes (C6,C7) to MEDIAN Nerve

1. Pronator teres : Median (C6,C7)
2. Flexor carpi radialis longus: Median (C6,C7)
3. Palmaris longus: Median (C6,C8)
4. Flexor digitorum superficialis: Median (C7,C8,T1)

Question 12

Radial Nerve
What Spinal root contributions (SRC)? 
Cord? 
13 Muscles?
10 Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 12

RADIAL NERVE
(C5,6,7,8,T1)
-From Posterior Cord (Posterior Divisions of all Trunks)

• Triceps, Brachioradialis, ECRL,ECRB,ED,EDminimi,ECU,AbPL,EPB,EPL,EIncicis,Supinator, Anconeus
• Extension of arm, forearm, wrist, digits 2-5, thumb, index finger. Elbow Flexion, supination, Abduct thumb, adduct wrist

Question 13

Lower Subscapular Nerve
What Spinal root contributions (SRC)? 
Cord? 
Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 13

Lower Subscapular Nerve
(C5, C6*)
Comes off Posterior Cord (PC comes from all trunks)

-Teres Major (Adduction, Medial Rotation of Humerus)

Question 14

Middle Subscapular Nerve 
What Spinal root contributions (SRC)? 
Cord? 
Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 14

Thoracodorsal Nerve
(C6,C7,C8)
Comes off posterior Cord (PC comes from all trunks)

Latissimus Dorsi (Extends, Adducts, Medial rotation Arm)

Question 15

Ulnar Nerve
What Spinal root contributions (SRC)? 
Cord? 
10 Muscles?
Action Disrupted if Lesion?
Cutaneous Distribution?

Answer 15

Ulnar Nerve

• (C8, T1)
• UN From Medial Cord (MC from inferior trunk)
• FCU, FDP medial head, PB, FPB deep head, AbDM,FDM,ODM, AdP, PADs, DABs

Actions: Flex & Adduct: Thumb, Wrist, Digit ab/ad duction
-abduct flex opposition digit 5

Question 16

Medial root of median nerve

Answer 16

Medial root of median nerve
(C8, T1)
FDP, PL, FPL, PQ, AbPB, FPB, OP, Lumbricals 1-4
Flex MCP joints, extend PIP, DIP joints,