The mamma or breast is made up of: (1) the mam- mary gland; (2) the fatty superficial fascia in which it is embedded; and (3) the overlying skin with the nipple and the surrounding pigmented skin—the areola [Fig. 3.8].
In the male, the mammary gland is rudimen- tary; the nipple is small, and the areola is com- monly surrounded by fine hairs. In the non-lac- tating female, the breast consists mainly of the fatty tissue of the superficial fascia, in which are enclosed 15 to 20 lobes of rudimentary glandu- lar tissue. These glands radiate outwards from the pierce the deep fascia in the neck. They cross the
clavicle to supply the skin on the front of the chest and shoulder [see Figs. 5.8, 5.9] down to a horizon- tal line at the level of the second costal cartilage.
They are named, according to their positions: me- dial, intermediate, and lateral.
The anterior cutaneous branches of the in- tercostal nerves (except the first and occasion- ally the second) emerge from the intercostal spaces near the lateral border of the sternum, pierce the pectoralis major, and supply the skin from the an- terior median line almost to a vertical line through the middle of the clavicle (mid-clavicular line) [see the course of the ventral rami in Fig. 1.5]. They are accompanied by perforating branches of the inter- nal thoracic artery, an artery which lies immedi- ately deep to the costal cartilages. In the female, these arterial branches are enlarged in the second to fourth spaces to supply the mammary gland.
The arteries have lymph vessels running with them from the skin of the anterior thoracic wall and the medial part of the mammary gland (breast) to parasternal nodes which lie beside the internal thoracic artery.
The lateral cutaneous branches of the in- tercostal nerves pierce the deep fascia along the mid-axillary line. Each nerve divides and enters the superficial fascia as anterior and posterior branch- es. The nerves pierce, or pass between, the digita- tions of the serratus anterior but play no part in supplying this muscle, the pectoral muscles, or the Fig. 3.7 Course and distribution of the supraclavicular nerves.
Accessory N.
Lateral supraclavicular N.
Intermediate supraclavicular N.
Trapezius
Medial supraclavicular N.
Sternocleidomastoid
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The pectoral region and axilla
to the gland and anchor it both to the skin and to the underlying deep fascia.
The base of the mammary gland extends from the margin of the sternum to almost the mid-axil- lary line, and from the second to sixth ribs. It lies largely on the pectoralis major muscle. Inferolat- erally, it extends on to the costal origins of the serratus anterior and the external oblique muscle nipple, giving the gland the shape of a flattened
cone. Each lobe has a main lactiferous duct which passes to open separately on the nipple. At the base of the nipple, the duct is dilated to form a lactiferous sinus. The gland has no capsule, but its lobes are separated by fibrous strands of the superficial fascia which pass from the skin to the deep fascia. These fibrous strands are attached
DISSECTION 3.1 Skin reflection of the front and side of the chest Objectives
I. To reflect the skin on the front and side of the chest.
II. To examine the superficial fascia. III. To find the cutaneous vessels and nerves.
Instructions
1. Make the skin incisions 1–4, shown in Fig. 3.3. Make sure to carry incision 4 backwards as far as the poste- rior axillary fold.
2. Cut through the superficial fascia in incisions 1, 3, and 4.
3. Start from the midline (incision 1). Reflect the flaps of skin and the superficial fascia laterally by blunt dissec- tion. Do not detach them. Leave the nipple and the surrounding skin in position as a landmark.
4. As the flap is separated from the skin of the neck along the clavicle, split the superficial fascia with a blunt instrument. Avoid cutting through the thin sheet
of muscle (platysma) and the supraclavicular nerves [Fig. 3.7]. The supraclavicular nerves pass anterior to the clavicle to supply the skin of the upper part of the anterior thoracic wall and the shoulder.
5. Identify the medial, intermediate, and lateral branches of the supraclavicular nerves.
6. Note the fibrous strands connecting the deep fascia to the skin, especially deep to the breast in the female.
7. Find the anterior cutaneous nerves and vessels which emerge from the anterior ends of the intercostal spaces.
Follow the branches of one of these nerves medially and laterally as far as possible.
8. Find the lateral cutaneous branches which pierce the chest wall in the mid-axillary line. They emerge through the deep fascia, one inferior to the other, in a vertical line. Follow the branches of one of them ante- riorly and posteriorly as far as possible.
Fig. 3.8 Dissection of the right mammary gland.
Pectoralis major muscle Pectoral lymph nodes Axillary tail
Lobule of gland
Lactiferous duct Lactiferous sinus Areolar gland Stroma Subcutaneous fatty tissue
Serratus anterior muscle
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Pectoral region
major to become continuous with the fascia of the axillary floor (axillary fascia). The axillary fascia stretches between the pectoralis major and the latissimus dorsi. When the arm is abducted, the axillary fascia rises into the axilla to form the armpit.
The clavipectoral fascia lies in the anterior wall of the axilla, deep to the pectoralis major. It extends from the clavicle to the axillary fascia and encloses the pectoralis minor and subclavius mus- cles [Fig. 3.10].
See Dissection 3.3 for instructions on dissecting the pectoral region.
of the abdomen. The ‘axillary tail’ arises from the superolateral quadrant of the breast and pass- es into the axilla, up to the level of the third rib [Fig. 3.8]. The apex of the gland—the nipple—
lies a little below the midpoint of the gland, ap- proximately at the fourth intercostal space in the nulliparous woman. The nipple is free of fat but contains circular and longitudinal smooth mus- cle fibres which can erect or flatten it. The skin of the nipple and areola contains modified sweat and sebaceous glands, particularly at the outer margin of the areola. These sebaceous glands tend to enlarge in the early stages of pregnancy, and shortly thereafter there is an increase in pigmen- tation in both the nipple and areola which never return to their original colour. In the later stages of pregnancy, the greater part of the fat in the gland is replaced by the proliferation of its ducts and the growth of many secretory alveoli from their branching ends.
The gland receives its blood supply from perfo- rating branches of the intercostal and internal tho- racic arteries medially and from the lateral thoracic artery laterally.
Lymph vessels drain principally: (a) to the axilla—(i) along the axillary tail to the pectoral lymph nodes, and (ii) through the pectoralis ma- jor and clavipectoral fascia to the apical axillary nodes via the infraclavicular nodes; (b) to the parasternal nodes along the internal thoracic artery by passing along the branches of that ar- tery which supply the gland; and (c) some lymph also drains to the posterior intercostal nodes. Since there is communication of lymph vessels across the median plane, there may be drainage to the oppo- site side, especially when some of the pathways are blocked by disease [Fig. 3.9].
Dissection 3.2 describes the dissection of the breast.
This is not usually very successful in the elderly female and should not be attempted in the male.
Deep fascia
The deep fascia covering the pectoralis major is continuous with the periosteum of the clavicle and sternum, and passes over the infraclavicular fossa and deltopectoral groove (between the pec- toralis major and the deltoid) to become continu- ous with the fascia covering the deltoid. It curves over the inferolateral border of the pectoralis
Fig. 3.9 Lymph nodes and lymph vessels of the axilla.
Clavicle
Subclavian lymph trunk Apical lymph nodes
Posterior lymph nodes Lateral lymph
nodes
Anterior lymph nodes Central lymph
nodes Lateral wall
Posterior wall
Anterior wall Medial wall
DISSECTION 3.2 The breast Objective
I. To identify the lactiferous ducts and lobes of the mammary gland.
Instructions
1. Attempt to pass a bristle through one of the ducts of the nipple.
2. Attempt to identify one of the lobes of the gland by blunt dissection.
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The pectoral region and axilla
the lateral lip of the intertubercular sulcus or crest on the humerus [see Fig. 5.1A]. At the insertion, the abdominal part twists under the sternocostal part to form a U-shaped tendon with it. The lowest abdomi- nal fibres are inserted deep to the upper sternocostal fibres, while the intermediate fibres form the base of the U in the anterior axillary fold.
The clavicular part passes inferolaterally, fuses with the anterior layer of the U-shaped tendon, and extends further inferiorly on the humerus. The clavicular part lies at right angles to the abdominal and lower sternocostal parts and has different ac- tions [Fig. 3.11].
Nerve supply: medial and lateral pectoral nerves. Actions: the pectoralis major adducts and medially rotates the humerus. With the arm above the head, the lowest fibres act with the latissimus dorsi to pull down the arm or raise the body, as in climbing a rope. The muscle can also return the ex- tended humerus to the anatomical position, then continue to flex the shoulder joint with its clavicu- lar part which passes in front of the shoulder.