Download Unit 5. Scapular Region, and Arm

Unit 5. Scapular Region, and Arm
Dissection Instructions:
Make an incision two millimeters deep from the shoulder region to the hand, then carefully reflect the skin
from the superficial fascia. (All of the skin from the upper limb should be removed except for the palm of the hand
and the fingers.)
Now clean the structures in the superficial fascia of the upper limb. On the dorsum of the hand locate the
veins and follow the larger ones proximally. In cleaning the superficial veins, be careful of the cutaneous nerves
which accompany them (Plates 452, 453; 6.4, 6.5). The cephalic vein begins on the dorsum of the hand on the
lateral or radial side. It ascends the forearm to the anterior lateral aspect at the elbow, and then goes to the
deltopectoral triangle where it was previously seen. The basilic vein begins on the medial side of the dorsum of
the hand and ascends to the anterior medial side at the elbow. Shortly above the elbow the basilic vein pierces the
deep fascia to join the brachial vein and form the axillary vein. In front of the elbow joint, the cephalic and basilic
veins are joined by the median cubital vein.
The cutaneous nerves of the hand and forearm are more easily found than those of the arm (Plates 452,
453, 454; 6.10a&b). The lateral antebrachial cutaneous nerve accompanies the cephalic vein in the forearm. It is
a continuation of the musculocutaneous nerve off the lateral cord of the brachial plexus and pierces the deep fascia
at the elbow after emerging from between the biceps brachii and brachialis muscles. It has anterior and posterior
branches to supply the forearm to the hand. The medial antebrachial cutaneous nerve pierces the deep fascia just
above the elbow and follows the basilic vein to innervate the skin to the hand. It is a direct branch off the medial
cord of the brachial plexus. On the dorsal side of the wrist, dorsal cutaneous branches of the superficial radial
nerve can be found laterally and dorsal cutaneous branches of the ulnar nerve can be found medially.
On the lateral side of the arm, a series of cutaneous nerves exit the deep fascia (Plates 452; 6.10a). The
upper lateral cutaneous branches of the axillary nerve appear around the posterior border of the deltoid muscle.
From the lateral intermuscular septum of the arm appear the lower lateral cutaneous nerves of the arm and the dorsal
antebrachial cutaneous nerve, both off the radial nerve. The latter nerve gives some branches in the region of the
arm and extends to the wrist. The intercostobrachial nerve and medial brachial cutaneous nerve were seen in the
axilla and now should be followed down the medial side of the arm. The posterior brachial nerve is a branch of the
radial as it leaves the axilla. The cutaneous veins and nerves should be preserved as the superficial fascia is
removed.
Clean the deltoid muscle (Plates 407, 415; 6.17, 6.38, Table 6.4 and figure-p. 496). . It takes origin from
the lateral end of the clavicle, acromion process and spine of the scapula and inserts on the deltoid tuberosity about
mid-way down the lateral surface of the humerus. Carefully detach its origin and reflect it away from the shoulder
so the axillary nerve and posterior humeral circumflex vessels can be cleaned (Plate 403, 404; 6.31, Table 6.1
and figure-p. 479). In cleaning the nerve, remember that it also supplies the teres minor. It enters this area from the
axilla by passing through the quadrangular space.
Clean the supraspinatus, infraspinatus, teres minor, and teres major muscles on the dorsal side of the
scapula (Plates 407-409; 6.36, 6.37, Table 6.5 and figures-p. 497). The trapezius muscle may be detached from the
scapula to adequately see the supraspinatus. The supraspinatus, infraspinatus and teres minor muscles insert on
the greater tubercle of the humerus. They, together with the subscapularis muscle, form the rotator cuff of the
shoulder joint (Plates 408; Table 6.5 and figures-p. 497). The teres major muscle arises from the inferior angle and
axillary border of the scapula close to the teres minor, but it passes anterior to the long head of the triceps brachii
and humerus to insert on the lesser tubercular ridge. The space between the teres muscles medial to the long head of
the triceps brachii is called the triangular space. The space between the teres muscles and between the long head
of the triceps brachii and humerus is called the quadrangular space. If the long and lateral head of the triceps
brachii are separated, the triangular interval is seen. The triangular space transmits branches of the circumflex
scapular vessels, but not the main trunks of the vessels, which remain on the surface of the scapula deep to the teres
minor and infraspinatus muscles. The quadrangular space contains the axillary nerve and posterior humeral
circumflex vessels, and the triangular interval has the radial nerve and deep brachial vessels deep to it. On one
side, cut the supraspinatus and infraspinatus muscles at the level of the lateral end of the spine of the scapula and
Unit 5 - 1
locate their nerve and blood supply, which passes deep to the muscles on the surface of the scapula. These are the
suprascapular nerve and vessels (Plates 409; 6.24, 6.25, 6.27, 6.37).
Clean the subscapularis muscle to its insertion on the lesser tubercle of the humerus and review its nerve
supply (Plates 409; 6.25, 6.32).
The anterior osteofascial compartment of the arm is sometimes called the flexor compartment (Plates 414,
457; 6.25, 6.32, 6.33, Table 6.6 and figures-p. 500). It contains the coracobrachialis, biceps brachii and brachialis
muscles, all of which are innervated by the musculocutaneous nerve and receive their blood supply by the
brachial vessels. Clean the coracobrachialis, biceps brachii, brachialis and triceps brachii muscles The
coracobrachialis muscle arises in common with the short head of the biceps brachii from the coracoid process of
the scapula. It inserts on the medial side of the humerus opposite the insertion of the deltoid muscle. The
musculocutaneous nerve usually passes through the coracobrachialis as it innervates it. The long head of the
biceps brachii is seen in the intertubercular sulcus before it enters the shoulder joint by passing under the transverse
ligament. Do not follow it into the shoulder joint at this time, but note that its origin is on the supraglenoid tubercle
of the scapula. The biceps brachii inserts on the radial tuberosity by a strong tendon. The bicipital aponeurosis is
a slip of fascia extending from the biceps tendon to the deep fascia over the flexor muscles of the forearm. The
bicipital aponeurosis separates the median cubital vein from the brachial artery and median nerve. Those attempting
to draw blood from the median cubital vein should keep this in mind (Plates 463; 6.49A & B).
The brachialis muscle arises from the front of the humerus and inserts on the ulnar tuberosity (Plates 414,
456, 457; 6.33). Elevate the biceps brachii from the brachialis and locate the musculocutaneous nerve. It supplies
both muscles, then continues as the lateral antebrachial cutaneous nerve. Clean the median nerve as it follows
the brachial artery through the arm. Typically, the nerve begins lateral to the artery, crosses superficial to it and lies
on its medial side as it enters the cubital fossa (Plates 416, 456, 458; 6.34, 6.49C&D)
Carefully clean the brachial artery preserving its branches (Plates 416, 417, 456; 6.11, 6.34, 6.49C&D).
Its first branch is usually the deep brachial artery, which will accompany the radial nerve through the arm. The
superior ulnar collateral artery also comes off high and accompanies the ulnar nerve to the elbow. Several
muscular branches supply the muscles of the arm. Above the elbow, the inferior ulnar collateral artery comes off
and passes in front of the medial epicondyle of the humerus. It also communicates with the superior ulnar collateral
and middle collateral arteries. Now clean the ulnar nerve through the arm. It has no branches here and passes
posterior to the medial epicondyle (Plates 415, 416, 459; 6.34, 6.51B&C). It is the "crazy bone".
The posterior osteofascial compartment of the arm contains only the triceps brachii muscle which is
innervated by the radial nerve. The deep brachial vessels are the principal blood supply. Clean the triceps brachii
muscle (Plates 415, 460; 6.36, 6.37). The long head arises from the infraglenoid tubercle and passes between the
teres major and minor muscles before joining the lateral head. The lateral head arises from the upper lateral surface
of the humerus lateral to the radial groove. The medial head arises from the back of the humerus below the radial
groove, starting above on the medial side but covering from medial to lateral epicondyles below. Elevate the long
and lateral heads of the triceps from the humerus and follow the radial nerve and deep brachial vessels to the lateral
intermuscular septum (Plates 415, 460; 6.24, 6.25, 6.36, 6.37, 6.49D). Clean the branches that innervate the
different heads of the triceps brachii muscle. Separate the brachialis and brachioradialis muscles on the lateral side
of the arm and locate the radial nerve as it enters the cubital fossa. In the back of the arm, the deep brachial artery
divides into middle and radial collateral arteries.
Be sure to identify all of the following in this unit
cephalic vein
basilic vein
lateral antebrachial cutaneous nerve
medial antebrachial cutaneous nerve
dorsal cutaneous br. of superficial radial nerve
upper lateral cutaneous of axillary nerve
deltoid muscle
axillary nerve
Unit 5 - 2
posterior humeral circumflex artery
brachial artery
deep brachial artery
superior ulnar collateral artery
inferior ulnar collateral artery
ulnar nerve
triceps brachii muscle all heads
intermuscular septum