Lab Manual - Pectoral Region & Breast

Assignments:

  1. Read the Lab Manual and Dissector Answers, view the Lab Video, and review the Prelab Images and the Prelab Learning Module.
  2. Read Woodburne & Burkel: 17-25, 107-114

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.

Summary of Dissection Procedure:

  1. Review the bony landmarks.
  2. Remove the skin from the chest wall as in Figure 2.
  3. Identify and reflect the pectoralis major muscle and identify its blood and nerve supply.
  4. Identify and reflect the pectoralis minor muscle, identify its blood and nerve supply and clavipectoral fascia.

Procedure:

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

Locate the following structures on the skeleton: crest of greater tubercle of the humerus; clavicle, suprasternal (jugular) notch, manubrium, sternal angle, body and xiphoid process of the sternum, coracoid process of the scapula.

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.

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