Axilla & Arm

Question 1

Name the muscles of the arm.

Answer 1

Anterior Compartment: coracobrachialis, biceps brachii, brachialis
Posterior Compartment: triceps brachii, anconeus

Question 2

Name the actions and innervation (including common spinal cord segments) of the anconeus.

Answer 2

C7-C8
Attachments: from lateral epicondyle of humerus to lateral surface of the olecronon process
Actions: extension of the elbow
Innervation: radial n.

Question 3

Name the actions and innervation (including common spinal cord segments) of the biceps brachii.

Answer 3

C5-C6
Attachements: from coracoid process (short head) and supraglenoid tubercle (long head) of the scapula to the radial tuberosity and the deep antebrachial fascia (through the bicipital aponeurosis)
Actions: flexion of the shoulder and elbow, and supination of the forearm
Innervation: musculocutaneous n.

Question 4

Name the actions and innervation (including common spinal cord segments) of the brachialis.

Answer 4

C5-C6
Attachments: from the distal anterior shaft of the humerus and lateral and medial intermuscular septa to the coronoid process and ulnar tuberosity
Actions: flexion of the elbow
Innervation: musculocutaneous n. And small branch of radial n.

Question 5

Name the actions and innervation (including common spinal cord segments) of the coracobrachialis.

Answer 5

C6-C7
Attachments: from the coracoid process to the proximal medial shaft of the humerus
Actions: flexion and adduction of the humerus
Innervation: musculocutaneous n.

Question 6

Name the actions and innervation (including common spinal cord segments) of the triceps brachii.

Answer 6

C6-T1
Attachments: from the infraglenoid tubercle of the scapula (long head), proximal posterolateral (lateral head), and distal postermedial (medial) shaft of the humerus to the olecranon process of the ulna
Actions: extension of the shoulder (long head), and extension of the elbow (long, lateral, and medial heads)
Innervation: radial n.

Question 7

Explain the boundaries and contents of the axilla.

Answer 7

Apex: 1st rib, clavicle
Base: skin of armpit
Anterior: pectoral muscle
Posterior: scapula, subscapularis mm.
Medial: thoracic wall, serratus anterior mm.
Lateral: humerus

Contents: axillary a., axillary v., axillary lymph nodes, 3 cords of the brachial plexus

Question 8

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

Answer 8

Roots: Long thoracic n. (C5-C7), and dorsal scapular n. (C4-C5)
Trunk: Upper —> subclavian n. (C5-C6), and suprascapular n. (C4-C6)
Divisions: none
Cords:
Lateral —> lateral pectoral n. (C5-C7)
Posterior —> upper and lower subscapular n. (C5-C6), and thoracodorsal n. (C6-C8)
Medial —> medial pectoral n. (C8-T1), m cutaneous n. Of arm and of forearm (C8-T1)
Nerves (terminal branches): musculocutaneous n. (C5-C7), axillary n. (C5-C6), radial n. (C5-T1), median n. (C5-T1), ulnar n. (C7-T1)

Question 9

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

Answer 9

Motor: innervation of skeletal mm.
Sensory: impulses from skin or proprioceptive organs in mm. (Gives status updates of length of mm. To N.S.)
Sympathetic (pre/post): innervation of smooth mm. Of blood vessel wall (postganglionic sympathetic axons go almost everywhere in the body)

Question 10

What is the naming convention for spinal nerves as they exit the vertebral column to the spinal nerves of the brachial plexus?

Answer 10

Cervical spinal nn. Exit above their corresponding vertebrae (C6 nerve in C5-C6 intervertebral space)
All other spinal nn. Exit below their corresponding vertebrae (T7 nerve in T7-T8 intervertebral space)
Exception: C8 exits between C7 and T1

The vertebral column is longer than the spinal cord because tissue growth rate of bone for outpaces that of the nervous system tissue.

Question 11

Use a drawing of the brachial plexus to locate a point that a single lesion would explain patient findings (sensory and motor deficits).

Answer 11

See drawing
If it’s a total lack of motion/inability to move problem is at peripheral level.
If it’s weakness, that’s segmental.
Deep radial n. Does all motor and superficial radial n does all sensory

Question 12

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

Answer 12

Triangular Space: circumflex scapular a.
- Borders teres minor, teres major, and long head of triceps brachii
Triceps Hiatus: radial n. And profunda brachii a.
- Borders: teres major superiorly, long head of triceps brachii medially, lateral head of triceps brachii laterally

Question 13

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

Answer 13

Contents: coracobrachialis, biceps brachii, brachialis
Actions: shoulder and elbow flexion, supination of forearm
Innervation: musculocutaneous n. (Off of lateral cord)
Arterial Blood Supply: brachial a.

Question 14

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

Answer 14

Contents: triceps brachii, anconeus
Actions: shoulder and elbow extension
Innervation: radial n. (Posterior cord)
Arterial Blood Supply: profunda brachii a.

Question 15

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

Answer 15

Head of humerus moves anteriorly out of GH joint from excessive abduction and lateral rotation of hand - causes GH ligament to tear

Question 16

Predict what neurovascular structures would be injured based on bone fracture located at the surgical neck of the humerus, radial groove of the humerus.

Answer 16

axillary n., circumflex humeral a., basilic v.

Question 17

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

Answer 17

C5 - deltoid tuberosity
C6 - thumb 
C7 - index finger
C8 - 5th digit (pinky)
T1 - medial aspect of forearm just below medial condyle

Question 18

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

Answer 18

H

Question 19

Identify structures of the Biceps Brachii Muscle Level

Answer 19

Kenhub