Lab Manual - Pectoral Region & Breast

Assignments:

Learning Objectives:

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

  1. Describe the general gross features of the breast and its blood supply.
  2. Describe the lymphatic drainage of the breast.
  3. Identify the muscles of the pectoral region, their related fascia, nerve and regional blood supply, and general functions.
  4. Describe the general features of the circulatory system.
  5. Identify and demonstrate the areas of distribution of the major cutaneous nerves of the upper limb.
  6. Identify and demonstrate the major superficial veins of the upper limb.

Procedure:

1. Review the bony landmarks. (Play movie; View images: N 185, 419, 420, 421, 439, TG 2-03A, 2-03B, 2-04, 4-04)

On a skeleton, review the following bony features of the upper limb: on the humerus, the head and anatomical and surgical necks, greater and lesser tubercles and their crests, the intertubercular or bicipital groove, deltoid tuberosity, and medial and lateral epicondyles; the styloid processes of the radius and ulna; on the scapula, the supraspinous and infraspinous fossae, scapular notch, and acromion process, coracoid process of the scapula and the clavicle, suprasternal (jugular) notch, manubrium, sternal angle, body and xiphoid process of the sternum.

Scapula and clavicle

Figure 2

2. Remove the skin from the chest wall as in Figure 2. (Play movie; View images: N 180, 182, 183, 184, 188, 189, 192, 257, 420, 427, 429, 430, TG 1-17, 2-10A, 2-10B, 2-11A, 2-11B, 2-12, 2-13, 2-15A, 2-15B, 4-02, 4-07, 4-11)

Remove the skin and subcutaneous tissue over the pectoral and anterior deltoid regions, down to about mid-brachium (Fig. 2).

The uppermost incision should directly overlie the clavicle. Make an encircling cut around the nipple and areola in the male, leaving them in place for future reference. Along the lateral margin of the sternum, identify anterior cutaneous branches of intercostal nerves. As you approach the anterior axillary line, use blunt dissection to find examples of lateral cutaneous branches of intercostal nerves in the superficial fascia running parallel to the ribs. Where do their anterior and posterior branches distribute? Identify several anterior branches of these nerves as they emerge along the anterior axillary line through the serratus anterior muscle. Observe serratus anterior arising from the anterolateral rib cage and passing backward to insert onto the vertebral border of the scapula.

Mammary gland. Incise through the nipple and areola with horizontal and vertical incisions. Is any pinkish glandular tissue visible? Normally no glandular elements are visible in the male. In the female, examine cut surfaces for lactiferous ducts and sinuses. Try to define a lobe. What are suspensory ligaments? Note attachments and location. Because of age and non-lactating condition of the gland, atrophy may be present and the internal structure hard to discern. It should be understood that in regard to female cadavers, nearly all of them, if not all, are elderly and postmenopausal and consequently many female structures influenced by female hormones will be difficult to demonstrate or identify throughout the body. Consider blood supply, nerve supply and lymphatic drainage. Note the position of the nipple in reference to the intercostal spaces.

Mammogram Breast cancer

3. Identify and reflect the pectoralis major muscle and identify its blood and nerve supply. (Play movie; View images: N 184, 188, 189, 420, 424, 427, 428, 429, 430, TG 2-12A, 2-12B, 2-13, 2-15A, 2-15B)

Clean the pectoralis major muscle and reflect it from its origins on the sternum and clavicle. (Caution: Do not cut deeply across the clavicular attachment in order to preserve the underlying nerves and vessels). Note pectoral (anterior axillary) lymph nodes deep to the lateral border of pectoralis major. Find the cephalic vein between adjacent borders of those muscles in the deltopectoral groove (or triangle). Follow the muscles to their insertions. Use blunt dissection to locate and identify the lateral pectoral nerve, medial pectoral nerve, pectoral branches of the thoracoacromial artery and vein as you clean. Why are lateral pectoral and medial pectoral nerves reversed from what you would expect?

Identify pectoralis minor muscle. Review its origin, course and insertion. Review the clavipectoral fascia.

Trace the lateral pectoral nerve, medial pectoral nerve, and branches of the thoracoacromial artery. Now trace the terminal part of the cephalic vein to the clavipectoral fascia. Where does the cephalic vein terminate?

4. Identify and reflect the pectoralis minor muscle, identify its blood and nerve supply and clavipectoral fascia. (Play movie; View images: N 184, 188, 189, 420, 424, 427, 428, 429, 430, TG 2-12, 2-15, 4-07)

Free the lateral border of the pectoralis major from the axillary fascia and reflect superiorly, taking care to preserve its vessels and nerves. Determine the manner of insertion of the sternocostal part. Next carefully reflect the pectoralis minor toward its insertion on the coracoid process. When this muscle is reflected the anterior wall of the axillary space has been removed. This space contains all of the neurovascular elements supplying the upper limb. They are for the most part embedded in fat and should not be dissected at this time; they will be considered later in the session on the axilla.

5. Skin the upper limb (except the palm of the hand). (Play movie; View images: N 428, TG 2-02, 2-12)

With the body on its back, skin the upper limb except the palm of the hand. Leave the superficial fascia intact.

6. Find the superficial veins and cutaneous nerves of the upper limb. (Play movie; View images: N 189, 418, 429, 430, 431, 432, 474, 476, 477, 478, 479, 480, 481, 482, 483, TG 2-02, 2-15, 2-17, 2-18, 2-20, 2-39, 2-47, 2-50, 2-51A, 2-51B, 2-52A, 2-52B, 2-53, 4-07)

Superficial veins. To demonstrate the veins, begin on the posterior side of the wrist and hand where the subcutaneous tissue is the thinnest and pick up any cutaneous vein, trace it toward the digits. Note that all veins are interconnecting, forming plexiform networks. Identify dorsal digital veins, intercapitular veins (what do these do? ), dorsal metacarpal veins. The dorsal venous network of the hand provides communication between adjacent dorsal metacarpal veins. The patterns of this plexus vary. Note this arrangement on the dorsum of your own and your partners' hands. Trace the ulnar continuation of this plexus as the basilic vein (or plexus of veins) along the ulnar border of the forearm. It continues to the arm and normally perforates the deep (brachial) fascia about 5 cm above the medial epicondyle of the humerus. Do not trace beyond this point. Does the vein perforate here in your cadaver? As you traced the basilic vein did you find accompanying nerves? What are these? Trace the radial continuation of the dorsal venous network as the cephalic vein along the radial border of the forearm and arm. Where does it terminate (perforate the deep fascia)? Does the vein extend into the arm? If not, where and how does it continue? Identify the nerve or nerves accompanying the cephalic vein. Note the anastomosis in the cubital fossa, the median cubital vein. What is its course and direction? Look at other arms to determine pattern. What are other variations? Note the perforating veins which communicate through the antebrachial fascia with deep veins especially one anchoring the median cubital vein.

Venogram of the cutaneous veins

The cutaneous nerves of the forearm and hand are more easily found than those of the back. Each perforates the deep (investing) fascia and enters the subcutaneous tissue at an identifiable location, where it is readily found. They may accompany specific veins or other identifiable structures. The cutaneous nerves of the arm and chest are branches of ventral primary rami of the spinal nerves, as are all subsequent nerves of the upper limb.

Locate, trace and determine area of cutaneous distribution of the following nerves. The lateral antebrachial cutaneous nerve perforates the deep fascia lateral to the tendon of the biceps and accompanies the cephalic plexus of veins. The medial antebrachial cutaneous nerve perforates the deep fascia medial to the tendon of the biceps and accompanies the basilic plexus of veins. The posterior antebrachial cutaneous nerve perforates the deep fascia 5 cm above the lateral epicondyle of humerus. The superficial branch of the radial nerve perforates the deep fascia along the radial border of forearm at approximately the junction of the middle and distal thirds of the forearm and accompanies parts of the cephalic venous plexus. Trace into the hand and identify its dorsal digital branches and their area of distribution. Do any branches communicate with branches of the ulnar nerve?

Locate the dorsal cutaneous branch of the ulnar nerve as it enters the subcutaneous tissue just distal to the ulnar styloid process. Trace distribution of its dorsal digital branches. Compare with other hands for variations in patterns.