Brachial plexus

Question 1

Describe the structure of the spinal nerves

Answer 1

Dorsal and central root come from the spinal cord

Both roots join to form the dorsal root ganglion => spinal nerve

3 branches

• post ramus
• ant ramus
• communicating rami <=> sympathetic chain ganglion

Question 2

Describe the locations of the dermatomes of the upper limb

Answer 2

C3, shoulder
C4, upper arm
C5, lateral  mid arm, forearm
C6, forearm and thumb
C7, middle 3 digits, middle of hand
C8, little finger
T1, medial surface of forearm
T2, medial surface of arm and axilla

Question 3

Describe the myotomes of the upper limb

Answer 3

C5, abduction of shoulder
C5-6, flexion at elbow
C6-8, extension at elbow
C7-8, flexion at finger
T1, abduction, adduction at finger

Question 4

Describe the axillary region

Answer 4

Area under the glenohumeral joint at the junction of the upper limb and thorax
A passage for neuromuscular and muscular structures between cervicoaxillary canal and axillary fossa

Question 5

What is the brachial plexus

Answer 5

All sensory innervation to upper limb and most of axilla
All motor innervation to upper limb and pectoral girdle expect trapezius
Passes under clavicle and pectoralis minor => upper limb

Question 6

What are the 5 roots of the brachial plexus

What nerves comes off the roots

Answer 6

C5-T1

C5, dorsal scapula
C5-7, long thoracic

Question 7

What are the 3 trunks of the brachial plexus

What nerves come off the trunks

Answer 7

C5-6, superior
C7, middle
C8-T1, inferior

Superior, suprascapular and subclavius

Question 8

Describe the divisions of the brachial plexus

Answer 8

All trunks have an anterior and posterior division

Superior posterior div, down to middle
Middle anterior div, up to superior
Inferior anterior div, up to middle

Question 9

`Describe the 3 cords of the brachial plexus

What nerves come off the cords

Answer 9

Superior => lateral
Middle => posterior
Inferior => medial

Lateral, lateral pectoral
Posterior, sup subscapular, thoracodorsal, inf subscapular
Medial, medial pectoral, medial arm cutaneous, medial forearm cutaneous

Question 10

Name the 5 terminal branches of the brachial plexus

Answer 10

Lateral => musculocutaneous and medial
Posterior => axillary and radial
Medial => Medial and ulnar

Question 11

What is the root of the dorsal scapular
What muscles does it innervate
What does it travel with
Does it pierce any muscles

Answer 11

C5

Rhomboids and levator scapulae

Dorsal scapular artery/transverse cervical

Pierces middle scalene

Question 12

What are the roots of the long thoracic
What muscles does it innervate
What does it travel with
What pathologies are associated with damage here

Answer 12

C5-7

Serratus anterior

C5-6 pierces middle scalene
C7 passes infront => descends post to brachial plexus, axillary artery and vein

Winged scapula

Question 13

What are the roots of the suprascapular
What muscles does it innervate
What does it travel with
What pathologies are associated with damage here

Answer 13

C4-6

Supraspinatus and infraspinatus, GH joint

Across suprascapular notch, under suprascapular ligament
Artery crosses above ligament

If suprascapular ligament ossifies, suprascapular nerve is compressed and paralyzed so cannot initiate abduction

Question 14

What are the roots of the lateral pectoral

What muscles does it innervate

Answer 14

C5-7

Pectorals major
Pectoralis minor via communicating branch => medial pectoral nerve

Question 15

What are the roots of the medial pectoral
What muscles does it innervate
What does it travel with

Answer 15

C8-T1

Pectoralis major and minor

Between axillary artery and vein, pierces pectoralis minor

Question 16

What are the roots of the axillary
What muscles does it innervate
What does it travel with
What other nerves branch off it

Answer 16

C5-6

Teres minor, deltoid, GH joint, skin of inferior deltoid

Leaves axilla via quadrangular space w post circumflex humeral

Gives superior lateral brachial cutaneous nerve => around surgical neck

Question 17

What are the roots of the musculocutaneous
What muscles does it innervate
What else does it innervate

Answer 17

C5-7

Ant arm comp (biceps brachialis, brachialis, coracobrachialis)
Supplies humerus as lateral cutaneous nerve of forearm

Question 18

What are the roots of the median
What muscles does it innervate
What does it travel with
What pathologies are associated with damage to the median nerve

Answer 18

C6-T1

Ant forearm comp and thenar eminence and lumbricals
Sensory innervation of lateral 3 1/2 digits and palm

Passes ant => cubital fossa => palm

Carpal tunnel syndrome

• median nerve passes under transverse carpal ligament with ant comp muscles
• rubbing => inflammation => distal paralysis

Question 19

What are the roots of the ulnar
What muscles does it innervate
What does it travel with
What pathologies are associated with damage to the ulnar nerve

Answer 19

C8-T1

1 1/2 ant forearm muscles (flexor corpi ulnaris, flexor digitorum profundis) and hand muscles
Sensory innervation of lateral 1 1/2 digits

Passes ant => behind med epicondyle => palm

Damage to ulnar => claw hand (can’t extend medical digits)

Question 20

What are the roots of the radial
What muscles does it innervate
What does it travel with

Answer 20

C5-T1

Post comp of arm and forearm

Post of humerus => ant lateral epicondyle => post forearm => back of the hand and medial 3 1/2 digits