Prelab Images - Pectoral Region, Posterior Shoulder & Breast

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Review the bony landmarks. (Play movie)

Crest of greater tubercle of humerus is labeled on plate N420 or TG2-03. The clavicle can be seen on plates N419 and N420 or TG2-03. The suprasternal (jugular) notch, manubrium, sternal angle, body, and xiphoid process of the sternum can be seen in plate N185 or TG4-04. The coracoid process can be seen anteriorly in plate N420 or TG2-03A and posteriorly in plate N421 or TG2-03B.

Step 2. Remove the skin from the chest wall as in Figure 2. (Play movie)

Perform this step the same way you skinned the back. Make a midline incision from the suprasternal notch to a couple inches below the xiphoid process and then make skin flaps like you have done before. Reflect the skin flaps laterally. Plates N180 or TG1-17, N258, and N192 or TG4-02 should give you an idea of where to look for the lateral and anterior cutaneous branches of the intercostal nerves. Plate N188 or TG2-12 is similar to what you will see in lab except you will have a lot of subcutaneous tissue on top of the muscle. The best view of the serratus anterior is plate N426. The long thoracic nerve comes from the brachial plexus (plate N430 and N429 or TG2-13) to innervate the serratus anterior (plate N426). The lateral thoracic artery branches off the axillary artery in plates N427 or TG2-15B and N429 or TG2-15A and supplies blood to the serratus anterior in plate N426. Plate N183 or TG4-07 is another view of the neurovascular supply of the serratus anterior. The insertion of the serratus anterior into the scapula is shown in plate N420 or TG2-06.

Plate N182 or TG2-10A and TG2-10B identifies the features of the breast. In lab you want to remove a section of the breast so you can have a view similar to this plate. Plate N183 or TG4-02 and TG2-11A shows the blood supply to the breast. Plate N184 or TG2-11B is an extremely important plate that shows the lymph drainage of the breast. Plates N188 or TG4-02 and N189 or TG4-11 show the course of the lateral cutaneous nerves that innervate the skin of the breast.

Step 3. Identify and reflect the pectoralis major muscle and identify its blood and nerve supply. (Play movie)

Pectoralis major is seen in plate N188 or TG2-12. The anterior axillary nodes are seen in plate N184 or TG2-11B. The cephalic vein in the deltopectoral groove is seen in plate N424 or TG2-12. You need to cut through the pectoralis major's attachment to the sternum and clavicle and reflect it laterally without damaging the underlying neurovasculature. The lateral pectoral nerve (supplies pectoralis major) and medial pectoral nerve (supplies pectoralis major and minor) both come from the brachial plexus (plate N430 or TG2-13). After reflecting pectoralis major your view will look something like plate N188 or TG2-12. The pectoral branch of the thoracoacromial artery is shown at its origin in plate N427 or TG2-15, perforating the clavipectoral fascia with the lateral pectoral nerve in plates N188 or TG2-12 and N428, and supplying pectoralis major and minor in plate N429 or TG2-15. The insertion of pectoralis major is seen in plate N420 or TG2-06.

Step 4. Identify and reflect the pectoralis minor muscle, identify its blood and nerve supply and clavipectoral fascia. (Play movie)

Pectoralis minor is seen covered in fascia in plates N428 and N188 or TG2-12 and cleaned in plate N189 or TG4-07. Clavipectoral fascia is labeled in plate N188 or TG2-12. Plates N430, N429 or TG2-15, N188 or TG4-07 may once again be helpful in tracing the neurovascular supply to pectoralis major and minor. Plates N428 or TG2-12, N429 and N189 or TG4-07 show the cephalic vein terminating into the axillary vein. Next, pectoralis minor must be reflected laterally by removing it from its origin on the ribs. The insertion of pectoralis minor on the coracoid process can be seen in plate N420 or TG2-06.

Step 5. Reflect deltoid muscle from acromion and spine of scapula. (Play movie)

Plate N424 or TG2-07 shows the deltoid muscle and plate N421 or TG2-06 shows its attachment to the scapula. Remove the deltoid from its attachment to the spine and acromion of the scapula and reflect it laterally to reveal the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) and teres major (seen in the right side of the posterior view picture of plate N424 or TG2-16A and TG2-16B). The axillary nerve can be seen in plates N430 and N429 or TG2-14 and TG2-08 at its origin and traveling through the quadrangular space in plate N426 or TG2-08 to innervate teres minor and deltoid muscles. The posterior circumflex humeral artery also travels through the quadrangular space in plate N426 and TG2-08 and can be seen in plates N427 or TG2-09 and N429 or TG2-15 as well. Supraspinatus can be seen in plates N424 or TG2-16A and TG2-16C, N425, and N426 or TG2-08. The origin and insertion of the deltoid and rotator cuff muscles can be seen in plate N420 or TG2-06A and N421 or TG2-06B.

Step 6. Saw off acromion and reflect the supraspinatus muscle. (Play movie)

Plate N425 or TG2-03 shows the junction of the spine of the scapula and the acromion process, which you must saw through. After sawing, you should be able to push the clavicle forward with the acromion process attached to it. The subacromial and subdeltoid bursae in plate N423 or TG2-42 may be visible after reflecting the acromion process. Plate N421 or TG2-06 shows the insertion of supraspinatus on the humerus. Reflect the supraspinatus by digging the muscle out of the supraspinous fossa starting from the medial side of the scapula so as not to damage the suprascapular artery and nerve seen in plate N426 or TG2-08. Plates N426 and N427 or TG2-09 show the suprascapular nerve and artery traveling through the suprascapular notch and supplying supraspinatus and infraspinatus muscles. Plate N421 or TG2-03 also labels the notch connecting the supraspinous and infraspinous fossae, which this neurovascular bundle must pass through.

Step 7. Reflect infraspinatus from the medial border of scapula toward shoulder and find nerves and vessels beneath. (Play movie)

Plate N426 or TG2-08 also shows the infraspinatus muscle. You must dig this muscle out of the infraspinatus fossa starting from the medial side of the scapula in order not to damage the more lateral suprascapular artery and nerve. Plates N33 or TG7-17 and N426 or TG7-15 show the course of the suprascapular artery from the neck to the scapula. Plates N430, N429 or TG2-15, and N426 or TG2-14 shows the suprascapular nerve branching from the superior trunk of the brachial plexus, joining the suprascapular artery and innervating supraspinatus and infraspinatus muscles.

Step 8. Dissect the teres minor and major muscles. (Play movie)

Teres minor is shown receiving innervation from the axillary nerve (N426 or TG2-08) and blood supply from the circumflex scapular artery (N427 or TG2-09). Its origin and insertion is shown in plate N421 or TG2-06. Teres major is seen receiving innervation from the lower subscapular nerve in plates N426 and N429 or TG2-15 and receiving blood supply from the scapular anastomoses in plates N426 or TG2-08 and N427 or TG2-09. Teres major can be seen joining latissimus dorsi in plate N424 or TG2-07 and running into the long head of triceps brachii in plate N426 or TG2-08. Plate N421 or TG2-06 shows the attachment of the long head of the triceps to the scapula. Plate N426 or TG2-08 illustrates the quadrangular and triangular spaces and their boundaries can be identified. Plate N427 or TG2-15 shows the circumflex scapular artery branching off the subscapular artery and plate N427 or TG2-09 shows this artery entering the scapular anastomoses.

Updated: 15 Sept 2011