Upper Extremity Week 2 Learning Objectives

Question 1

Explain the boundaries and contents of the axilla

Answer 1

Axilla boundaries:
Apex: 1st rib, clavicle
Base: skin of armpit
Anterior: pectoral mm.
Posterior: scapula, subscap m.
Medial: thoracic wall, serratus ant. m.
Lateral: humerus

Axilla contents:
Axillary a., axillary v., axillary lymph nodes, 3 cords of the brachial plexus

Question 2

Name the common spinal cord segments present in the 16 peripheral nerves of the brachial plexus.

Answer 2

C5-T1

Roots, 5 (ventral rami, [C4]C5-T1)
Trunks, 3 (upper, middle, lower)
Divisions, 3 ant, 3 post
Cords, 3 (med, lat, post)
Nerves (terminal brr.), 5

Additional 11 brr. (16 total)

Question 3

Name the functions (sensory, motor, postgang symp) of the axons present in the peripheral nerves of the brachial plexus.

Answer 3

Motor - Innervation of skeletal muscle

Sensory - Impulses from skin or proprioceptive organs in muscles (proprioception from muscle spindles on muscle length)

Sympathetic (pre/post) - Innervation of smooth muscle of blood vessel wall (postganglionic is in all ventral rami (?))

Question 4

Apply the convention for naming spinal nerves as they exit the vertebral column to the spinal nerves of the brachial plexus.

Answer 4

Cervical spinal nn. exit above their corresponding vertebrae:
C6 nerve = C5-C6

All other spinal nn. exit below their corresponding vertebrae:
T7 nerve = T7-T8

Question 5

Describe the location and contents of the following neurovascular tracts: triangular space, triceps hiatus.

Answer 5

Triangular space: circumflex scapular artery

Triceps hiatus: radial nerve, profunda brachial artery

Question 6

Describe the fascial compartments of the ANTERIOR arm and list their contents, general actions, innervation, and arterial supply.

Answer 6

Superficial muscles:
biceps brachii long head, biceps brachii short head

Deep muscles:
coracobrachialis, brachialis

Functions:
Shoulder & elbow flexion

Innervation:
Musculocutaneous n.

Arterial supply:
Brachial a.

Question 7

Describe the fascial compartments of the POSTERIOR arm and list their contents, general actions, innervation, and arterial supply.

Answer 7

Muscles:
triceps brachii long head, triceps brachii medial head, triceps brachii lateral head, anconeus

Function
Shoulder & elbow extension

Innervation
Radial n.

Arterial supply
Profunda brachii a.

Question 8

Predict the most common direction of dislocation of the shoulder based on the structure of the joint capsule and ligaments.

Answer 8

Shoulder dislocation:

• GH joint most frequently dislocated
• Inferior joint capsule not reinforced by rotator cuff muscles or ligaments
• Vulnerable to dislocation when arm is in abducted position (downward force)
• 95% of shoulder dislocations are anterior dislocations (inferiorly dislocated, then head of humerus moves anteriorly to GH space)

Question 9

Predict what neurovascular structures would be injured based on bone fracture located at the surgical neck of the humerus, radial groove of the humerus. The patient would probably exhibit paralysis of what muscle?

Answer 9

Surgical neck of the humerus:

• posterior circumflex artery
• anterior circumflex artery
• axillary nerve

Radial groove of the humerus:

• profunda brachii artery
• radial nerve

Question 10

Locate the areas of skin associated with a single spinal segment/nerve (dermatome).

Answer 10

Relevant dermatomes:
C5 - deltoid tuberosity
C6 - thumb
C7 - index finger
C8 - 5th digit
T1 - medial aspect of forearm, just below medial condyle

Question 11

Describe territories and path of drainage of axillary lymph nodes to the venous system.

Answer 11

SEE LYMPHATIC DRAINAGE DRAWING.

SEE VENOUS DRAINAGE DRAWING.

Question 12

Identify the joints of the elbow and provide their synovial classification on the Structure Information List.

Answer 12

Humeroulnar - Hinge (primary elbow joint)

Humeroradial - Gliding

Proximal radioulnar - Pivot joint (pronation/supination)

Question 13

Identify the functions and attachments of the ligaments of the elbow and forearm on the Structure Information List.

Answer 13

Radial collateral ligament:
function- resists excessive cubital varus
attachments- from lateral epicondyle to anular ligament

Ulnar collateral ligament:
function - resists excessive cubital valgus
attachments- from medial epicondyle to medial margin of coronoid process & olecranon process

Annular ligament:
function- stabilizes proximal radioulnar joint
attachments- from the anterior margin of the radial notch to posterior margin of radial notch surrounding head of radius

Interosseous membrane:
attachments- from interosseous border of radius to interosseous border of ulna

Question 14

Describe the location and function of the bursae at the elbow.

Answer 14

Subcutaneous bursa of medial epicondye

Subcutaneous bursa of lateral epicondyle

Bursa of anconeous

Bursa at origin of extensor carpi radialis brevis

Olecranon bursae

• subtendinous
• intratendinosus
• subcutaneous

Function

• cushion
• reduce friction between bone and ligament

Question 15

Describe the following injuries and relate anatomical structures to each: radial head subluxation.

Answer 15

“Nurse maid’s elbow” - Radial dislocation - pediatric elbow

• Force (distraction) causes radial head to subluxate from annular ligament
• Visible by lateral protruding lump caused by displaced head of radius (muscle pulls radial head superiorly from joint space)
• Caused by hanging/lifting from forearm, wrist, or hand. Distraction force pulls radial head out from annular ligament.
• Can occur in kids 3-7 y/o, most common from 3-5 y/o
• Radial head is not fully ossified, still primarily cartilage

Question 16

Describe the following injuries and relate anatomical structures to each: olecranon bursitis.

Answer 16

• Caused by continued excessive pressure to bursa (leaning on elbow for extended period of time or post-op shoulder in ill-fitting sling)
• Body over produces fluid to protect area
• Can usually self-resolve with compression, although sometimes may be drained by surgeon.

Question 17

Describe the fascial compartments of the anterior forearm and list their contents, general actions, innervation, and blood supply.

Answer 17

Superficial layer:
Contents - Pronator teres, Flexor carpi radialis (FCR), Palmaris longus
Innervation - Median N.

Contents - Flexor carpi ulnaris (FCU)
Innervation - *Ulnar nerve (exception to general rule that anterior compartment is innervated by median n.)

Intermediate layer:
Contents - Flexor digitorum superficialis (FDS)
Innervation - Median N.

Deep layer:
Contents - Flexor digitorum profundus (FDP)
Innervation - *Medial/ulnar portion ulnar nerve (medial - digits 2-3, ulnar - digits 4-5)

Contents - Flexor pollicis longus (FPL), Pronator quadratus
Innervation - Anterior Interosseus nerve from Median N.

Question 18

Predict what neurovascular structures would be injured based on bone fracture located at the medial epicondyle of the humerus.

Answer 18

Superior ulnar collateral artery, inferior ulnar collateral artery

Ulnar nerve

Basilic vein

Question 19

Describe the fascial compartments of the posterior forearm and list their contents, general actions, innervation, and blood supply.

Answer 19

Extension & supination

Superficial & deep layers

Radial nerve innervation

Radial artery (post. interosseus)

Superficial layer:
6 muscles
Brachioradialis
Extensor carpi radialis longus (ECRL)
Extensor carpi radialis brevis (ECRB)
Extensor digitorum
Extensor digiti minimi (EDM)
Extensor carpi ulnaris (ECU)

Action - Extension

Deep layer:
Supinator
Extensor indicis

(Outcropping thumb muscles)
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
- turns at dorsal tubercle of radius