Lab Manual - Axilla, Arm, & Shoulder Joint

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Review the lymphatic drainage of the upper limb and the major lymphatic node groups of the axilla. (explanation)
  2. Recall the concept of the axilla as a space, its boundaries and its contents. (explanation)
  3. Illustrate or describe the brachial plexus, including its parts, the nerves arising from it, and their specific origins and areas of distribution. (explanation)
  4. Predict the functional and cutaneous loss that might result in the back, posterior shoulder, pectoral region, or cutaneous upper limb, given an injury to a specific site in the brachial plexus. (explanation)
  5. Identify or describe the axillary artery and vein, their major branches, and their relationships to each other, the brachial plexus, and the pectoralis minor muscle. (explanation)
  6. Review the posterior shoulder muscles and associated rotator cuff muscles. Give their general functions and nerve supply. (explanation)
  7. Identify and demonstrate the regional blood supply to the shoulder. (explanation)
  8. Identify prominent features of the humerus, scapula, and cubital fossa as given in the lab manual. (explanation)
  9. Identify the contents of each of the three compartments of the arm and the functional significance of the included muscles. (explanation)
  10. Correlate any fractures of the humerus with functional disruptions of associated muscular and neurovascular structures. (explanation)
  11. Describe the movements of the shoulder joint. (explanation)
  12. Identify spatial relationships of all associated muscular and neurovascular structures within the cubital fossa. (explanation)

Readings and Modules:

Special note: please use the brachial plexus modules below.

Procedure:

1. Review the bony landmarks. (Play movie; View images: N 419, 420, 421, 436, 439, TG 2-03A, 2-03B, 2-04)

Identify the following structures on the skeleton and palpate on the cadaver and yourself or partner: acromion process, spine, supraspinatus and infraspinatus fossae, borders, and angles of the scapula; scapular notch; acromial half of the clavicle; the head, neck (anatomical and surgical), the bicipital (intertubercular) groove, deltoid tuberosity, greater and lesser tubercles and crests, radial groove, medial and lateral epicondyles of the humerus, the olecranon process and coronoid process of ulna, the styloid process of the ulna, and the head of radius, neck of radius, tuberosity of radius, and styloid process of the radius.

Bones of the shoulder

2. With the arm abducted, remove the fat and lymph nodes from the axilla. (Play movie; View images: N 181, 184, 189, 424, 427, 429, 430, TG 2-07, 2-11, 2-12, 2-14, 2-15A, 2-15B, 4-02, 4-08)

Reflection of the pectoralis major and minor muscles (the anterior wall of the axilla) has exposed the fat-filled axillary space. Within this fat lie the axillary vein and its tributaries, the axillary artery and its branches, the brachial plexus, and axillary lymph nodes. This dissection consists of complete removal of the fat to expose the above structures and define the limits and boundaries of the space.

Axillary lymph node locations
Abnormal axillary lymph nodes
Axillary artery and branches

Abduct the arm. Throughout the dissection look for lymph nodes and note their position. If normal, they are very small and inconspicuous. Squeezing the fat through your fingers will assist you in locating these "non-compressible" lumps. After locating one, incise to determine if it is a node (nodes are pinkish) or just fat. Correlate the locations with the five defined groups of axillary nodes: pectoral (anterior), lateral, subscapular (posterior), central and apical. Review lymphatic drainage of the mammary gland and upper limb.

Define the boundaries of the axillary space. Note that the anterior axillary fold (lateral border of pectoralis major) and the posterior axillary fold (latissimus dorsi and teres major), along with the axillary fascia, define the base of this space (armpit).

Dissection through the fat and connective tissue of the axilla is facilitated if one system is dissected (traced) at a time (first veins, then nerves, then arteries), rather than simultaneously trying to trace them together.

3. Cut and remove the middle third of the clavicle. Cut the axillary vein lateral to its junction with cephalic vein and remove axillary vein and tributaries. (Play movie; View images: N 32, 33, 184, 429, 435, TG 2-15, 2-53, 7-14, 7-15A, 7-15B)

In order to better observe the brachial plexus, cut and remove the middle third of the clavicle.

The major neurovascular structures in the axilla are bound together in a fibrous covering, the axillary sheath, which encloses the vessels and nerves as they pass between the scalene muscles in the neck.

The most superficial (anterior) structure is the axillary vein. Trace from the clavicle to the lateral border of the teres major tendon. How is it formed? Is it a single or paired vein or perhaps plexiform? Trace its tributaries as far as possible without invading other areas. Do its tributaries correspond to the axillary arterial branches? Are its tributaries paired (venae comitantes)? Note termination of the cephalic vein.

Can you see any valves in the veins? The presence of valves is usually exaggerated by the back flow pressure of embalming. Establish relationships of axillary artery and vein within the axilla. Completely remove the vein and its tributaries by cutting at the lateral border of the first rib and reflecting toward the arm.

4. Separate all brachial plexus nerves and axillary artery branches. (Play movie; View images: N 189, 426, 427, 429, 430, 435, 473, 474, 475, 476, 477, 478, 481, TG 2-07, 2-08, 2-14, 2-15A, 2-15B, 2-17A, 2-17B, 2-18, 2-20, 2-47, 2-50A, 2-51A, 2-51B, 4-07, 4-08)

Pick up branches of the brachial plexus and clear of fat: 1) lateral cord (above artery); lateral pectoral nerve, musculocutaneous nerve (entering coracobrachialis muscle); contribution to median nerve (anterior to artery); 2) medial cord (below or caudal to artery);medial pectoral nerve, contribution to median nerve; median nerve (anterior to artery); ulnar nerve (below artery, continuation of medial cord); medial antebrachial cutaneous n., a branch of the medial cord paralleling the ulnar nerve. Note communicating arch between medial and lateral cords. Do you see a separate medial brachial cutaneous n.?

Pick up the musculocutaneous, median and ulnar nerves together and note "M" pattern of formation leading to medial and lateral cords. Behind this arrangement is the axillary artery. Elevate the artery and locate the 3) posterior cord and its continuation, the radial nerve. Locate the axillary nerve (review boundaries of the quadranglar space and its contents). What artery will accompany the nerve? Identify the thoracodorsal nerve (accompanying artery?). Now look for the upper subscapular nerve to the subscapularis muscle (the accompanying artery is a muscular branch of the axillary artery to the subscapularis muscle). Identify the lower subscapular nerve to the teres major and subscapularis muscles. What does it accompany? Note the relations of the three cords to the axillary artery behind the pectoralis minor muscle. Trace the three cords proximally to define trunks, noting relations to axillary artery and how the cords are formed or derived from the trunks.

Beginning at the lateral border of the first rib, clean the axillary artery to the lateral border of the teres major muscle. Note course and relations throughout the axilla. Parts? How defined? Identify and trace each of its branches: superior thoracic a.; thoracoacromial, lateral thoracic, subscapular and its branches, the thoracodorsal artery and circumflex scapular artery, anterior and posterior circumflex humeral artery. For each, note point of origin (relative to pectoralis minor and other branches) and area of distribution. Note any accompanying nerves.

Remove remaining fat from axilla; define its shape and boundaries. Examine subscapularis and serratus anterior muscles. Locate the long thoracic nerve on serratus anterior (source?). What is "winged scapula"? Note also lateral cutaneous branches of intercostal nerves. Note that the lateral cutaneous branch of the second intercostal nerve (T2), called the intercostobrachial nerve, supplies the medial side of the arm.

5. Review teres minor and major musculature. Review triangular and quadrangular spaces. (Play movie; View images: N 421, 424, 426, 427, 429, TG 2-06, 2-07, 2-08, 2-09, 2-15A, 2-15B)

Remove the muscular fascia and locate the origin of the muscle from the inferior angle and the lower third of the lateral border of the scapula. Trace the muscle laterally until it joins the latissimus dorsi. Note that the two muscles travel together and are adherent as they pass to the anterior side of the humerus. Do not trace to their insertions at this time. Remove, carefully, the large masses of fat and connective tissue found in this area. As you trace the teres major laterally you will run into the long head of the triceps brachii overlying it on its dorsal side.

Clean the long head of triceps as it continues upward to attach to the infraglenoid tubercle of the scapula. This muscle forms a boundary between two spaces along the lateral border of the scapula: the triangular space and the quadrangular space. What are the boundaries of the quadrangular space? What does it transmit? Find the circumflex scapular artery in the triangular space and trace its branches and its course into the infraspinatous fossa. Is there an open anastomosis between it and the suprascapular artery? What does it supply? Does it anastomose with the suprascapular artery? What is the significance of this anastomosis? Review the arteries that you have dissected that supply the scapular region. The nerve to teres major will be identified in a later dissection. Consider the actions of the posterior shoulder muscles, concentrating on functional groups.

6. Open the arm compartments. (Play movie; View images: N 184, 420, 421, 426, 429, 431, 433, 434, 435, 447, 473, 474, 475, 476, 477, 479, 480)

Remove the superficial fascia from the arm and cubital fossa and expose the deep (investing) fascia, the brachial fascia. Note that it forms a complete sheath for the arm, and is continuous with fascia of the deltoid, the fascia of the muscles forming the posterior and anterior axillary folds, the axillary fascia, and with the antebrachial fascia (deep, investing) of the forearm. It divides the arm into anterior, posterior and neurovascular compartments by means of the medial and lateral intermuscular septa, which attach to the humerus.

Make a vertical incision through the brachial fascia of the anterior compartment in the anterior mid-line and reflect flaps medially and laterally. Identify medial and lateral intermuscular septa extending inferiorly from the insertions of coracobrachialis and deltoid, respectively. Note length and attachments of each. Do muscles use these septa as attachments? Examine muscles of the anterior compartment.

Biceps brachii. Do not follow the long head through shoulder joint to its origin. Observe the short head, the bicipital aponeurosis, and its radial insertion as the cubital fossa is examined.

Coracobrachialis. Note combined origin from the coracoid process with the adjacent short head of the biceps. Note again the insertion of pectoralis minor. Note course of the musculocutaneous nerve as it pierces coracobrachialis.

Brachialis. Note origin from medial and lateral intermuscular septa. The insertion will be more clearly seen when the cubital fossa and elbow joint are examined. Trace the musculocutaneous nerve through the anterior compartment noting course, relations, and branches innervating anterior compartment muscles. Where do they enter muscles? How does this nerve terminate? Where does it change its name? Do any arteries accompany it?

Medial to the anterior compartment of the arm, open the neurovascular compartment. How is it formed? Pick up the median nerve in the axilla and trace to the cubital fossa. What are its relations? Does it have any branches? Trace the ulnar nerve from the axilla and note relations. Where does it leave the neurovascular compartment? Does it have any branches in the arm? Is it accompanied by vessels? Trace the medial antebrachial cutaneous nerve from the medial cord throughout the neurovascular compartment, noting relations and point at which it enters the subcutaneous tissue. Pick up the radial nerve lying on the tendon of latissimus dorsi, locate the branches to the long head and medial head of the triceps. Again trace the radial nerve to the back of humerus.

Trace the brachial vein. Is it paired? How is it formed? What does it continue as? Where does the basilic vein join it?

Trace the brachial artery, indicating source, arbitrary point of inception, termination into what branches, course through arm and cubital fossa, and relations. Trace its branches and their points of origin from the brachial artery. What are its collateral branches around the elbow?

The cubital fossa is the triangular space in front of the elbow. Define and clean the margins of the muscles which bound it. Trace the tendon of the biceps to its insertion. Examine the bicipital aponeurosis, cut its attachment to the antebrachial fascia. Locate the brachial artery and median nerve. What are their relative positions? Where does the brachial artery divide? What happens to the median nerve? Separate the brachialis from the brachioradialis muscle along the intermuscular septum between them and identify the radial nerve. Is it accompanied by vessels? What are they? Clear brachialis as much as possible at this time.

What structures in the superficial fascia overlie the cubital fossa? What is their importance? Danger? Palpate on your partners the tendon of biceps and the brachial artery, and identify the median cubital vein.

Surface features of the cubital fossa
Angiogram of the axillary vessels

7. Cut the lateral head of the triceps obliquely in the direction of the radial groove to expose the radial nerve and deep brachial artery. (Play movie; View images: N 421, 432, 473, 476, 477, 478)

Cut through the brachial fascia of the posterior compartment in the dorsal mid-line, reflect flaps, open compartment, and again define medial and lateral intermuscular septa as before. Examine triceps brachii. The long head has previously been defined as a boundary of the triangular and quadrangular spaces.

Trace the lateral head until it joins the long head and inserts into the olecranon process. Insert a probe along the course of the radial nerve as it passes deep to the triceps. Carefully cut through the lateral head of the triceps by cutting down to the probe. The incision is an oblique one paralleling the radial groove of the humerus (refer to humerus). This will expose the course of the radial nerve, the deep brachial artery and vein and the origin of the medial head of the triceps covered by the fused long and lateral heads. After defining branches of the radial nerve to medial and lateral heads of the triceps, trace the nerve around the lateral border of the humerus until it enters the anterior compartment. (Under cover of what muscles?) What nerve is given off to the forearm at this point? Trace the deep brachial artery and its continuation, the radial collateral artery. Note the arrangement of veins.

Note ulnar nerve in the posterior compartment lying just behind the medial epicondyle. Palpate the ulnar nerve in your own arm. Note its relation to the superior ulnar collateral artery. Note the anconeus muscle.

MRI of upper limb muscles
MRI of triceps

 

Updated: 24 Oct 2011