PECTORAL REGION – INTRODUCTION
I. SKIN AND FASCIA
A. Superficial fascia composed of loose connective tissue
B. Contains sweat glands, blood, lymphatic vessels and nerves
C. Deep fascia is thin and dense - envelopes underlying musculature - send septa into muscle
D. Attached to periosteum of bone
II. BREAST
A. Generalities
1. Similar in male and female until puberty
2. Both have glandular tissue, mostly ducts
3. Nipple at level of 4th interspace (in nulliparous women, varies in multiparous)
4. Modified sweat glands
B. Gross morphology
1. Extent
a. From ribs 2-6
b. From lateral sternum to beyond anterior axillary fold
c. Axillary tail (of Spence) - part extending along pectoralis major muscle and axilla - most glandular tissue here
2. Plane - in superficial fascia, anterior to pectoralis major(2/3) and serratus anterior mm.(1/3)
3. Lobes - 15-20 separate lobes
a. each lobe has a single lactiferous duct - opens on nipple
b. dilate as lactiferous sinus prior to termination-milk accumulation
4. Connective tissue septa between lobes
5. Suspensory ligaments (Cooper’s ligaments) (Retinacula Cutis)
a. fibrous band connects gland to skin
b. runs between skin and deep fascia
c. Helps support lovules of the gland
6. Areolae - pigmented skin around nipple - contain sebaceous glands
7. Retromammary space(bursa) - between breast and deep fascia-allows movement
C. Arterial supply
1. Most enter from superior aspect
2. Internal thoracic artery - anterior perforating branches
3. Lateral mammary arteries - from lateral thoracic a. (br. of axillary a.)
4. Thoracoacromial
5. Posterior Intercostal aa.-lateral cutaneous branch of posterior intercostals
6. Superior epigastric
D. Veins
1. correspond to arteries - drainage to axillary vein and internal thoracic
E. Nerves
1. cutaneous nerves of anterior thoracic wall - discussed later
2. intercostal nn. T2-7
F. Lymphatics
1. Clinically important because of frequency of cancer in breast & metastasis via lymphatic channels
2. Lateral part - drains to axillary nodes (pectoral group) – 70%
3. Medial part - drains to retrosternal (parasternal) nodes along internal thoracic artery
4. Axillary nodes
a. Groups
i. pectoral group: deep to pectoralis major m., along pectoralis minor
ii. lateral group: along distal axillary vein
iii. subscapular group: along subscapular vessels
iv. central group-along axillary v.
v. apical group: apex of axillary near 1st rib - drains into subclavian lymph trunk > subclavian vein
b. Drainage - toward more medial groups - all eventually to apical group
G. Accessory drainage - sometimes bypasses pectoral group and drains directly to central or apical nodes
H. Sometimes lymph drainage is subdivided:
1. cutaneous plexus - can cross midline
2. subareolar plexus
3. deep plexus
I. Embryology
1. Develop as modified sweat glands (ectodermal origin)
2. Milk lines (mammary ridges) - strips of ectoderm along which mammary tissue can develop
3. Abnormalities
a. polymastia - extra breast
b. polythelia - extra nipple
c. gynecomastia - abnormal (excessive) development of breast tissue in male
III. PECTORAL REGION CONTENTS
A. Mammary glands
B. Muscles
1. Pectoralis major
2. Pectoralis minor
3. Subclavius
4. Serratus anterior
C. Deltopectoral triangle
1. Borders
a. pectoralis major – (medial border)
b. deltoid m. – (lateral border)
c. clavicle – (superior border)
2. Contents
a. Cephalic vein
b. Deltoid br. of the thoracoacromial a.
3. Pectoral fascia - invests p. major >> abdomen, clavicle, sternum and axilla
D. Clavipectoral fascia
1. fibrous sheet
2. runs from clavicle superiorly to axillary fascia inferiorly
3. invests pectoralis minor, subclavius
4. costocoracoid membrane - laterally
5. perforated by cephalic vein, thoracoacromial artery, lateral pectoral nerve
E. Medial and lateral pectoral nerves - from brachial plexus
1. medial pectoral nerve - to pectoralis major and minor - from medial cord of br. plexus-through pec.minor
2. lateral pectoral nerve - to pectoralis major - from lateral cord of br. plexus
IV. MUSCLES
A. Pectoralis major
1. Attachments: Clavicle (sternal portion), sternum to 7th rib, cartilages of true ribs to biceptal groove of humerus
2. Nerve: medial and lateral pectoral - from brachial plexus
3. Artery: pectoral br. of thoracoacromial, internal thoracic
4. Action: adducts arm, draws it forward and rotates medially
B. Pectoralis minor
1. Attachments: upper margin ribs 3-5 to coracoid process of scapula
2. Nerve: medial pectoral
3. Artery: thoracoacromial and intercostals, lateral thoracic
4. Action: pulls scapula forward and down