Thorax: Mammary Gland

Thorax > Mammary Gland > Study Aims
STUDY AIMS
At the end of your study, you should be able to:
Identify the mammary gland
Identify the location of the gland
Locate the blood supply of the breast
Understand the lymphatic drainage of the breast
Know how to palpate the breast

Thorax > Mammary Gland > Guides
GUIDES

3-2: Thorax—Mammary Gland (Plate 182) ( Fig. 3-2-1)
  • Consists of glandular tissue in which the majority is embedded within the tela subcutanea (superficial fascia) of the anterior chest wall overlying the pectoral muscles.
  • The glands are rudimentary in males and immature females.
  • Size and shape of the adult female breast varies; the size is determined by the amount of fat surrounding the glandular tissue.
  • The base of the breast is fairly consistent part, extending from the lateral border of the sternum to the midaxillary line and from the 2nd to the 6th ribs.
  • The majority of the breast overlies the deep pectoral fascia of the pectoralis major muscle, with the remainder overlying the fascia of the serratus anterior.
  • The breast is separated from the pectoralis major muscle by the retromammary space, a potential space filled with loose connective tissue.
  • The breast is firmly attached to the overlying skin by condensation of connective tissue called the suspensory ligaments (of Cooper), which help to support the lobules of the breast.
  • A small part of the mammary gland may extend toward the axilla, called the axillary tail (of Spence).
    Structure of the Breast
  • For descriptive purposes, the breast is divided into four quadrants: upper and lower lateral, and upper and lower medial.
  • The most prominent feature of the breast is the nipple.
  • The nipple is surrounded by the areola, a circular pigmented area of skin.
  • The areola is pink in Caucasians and brown in African and Asian people.
  • The pigmentation of the areola increases during pregnancy.
  • The areola contains sebaceous glands, following a pregnancy secrete an oily substance to protect the mother's nipple from irritation during nursing.
  • The breast is composed of 15 to 20 lobules of glandular tissue, formed by the septa of the suspensory ligaments.
  • The mammary glands are modified sweat glands that are formed from the development of milk-secreting alveoli, arranged in clusters.
  • Each lobule is drained by a lactiferous duct.
  • Each lactiferous duct opens on the nipple.
    Vasculature of the Breast (Plate 183)
  • Blood supply of the breast arises from the perforating branches and anterior intercostals branches of the internal thoracic artery.
  • The breast is also supplied by the branches of the thoracoacromial and lateral thoracic arteries (from the axillary artery).
  • Venous drainage parallels the arterial supply and is mainly to the axillary artery and internal thoracic vein.
    Lymphatic Drainage of the Breast ( Plate 184)
  • Lymph from the nipple, areola, and lobules of the mammary glands drains to a subareolar lymphatic plexus.
  • From there, a system of interconnecting lymphatic channels drains lymph to various lymph nodes.
  • The majority of the lymph, especially from the lateral quadrants of the breast, drains to the pectoral nodes, and from there to the axillary nodes.
  • The remaining amount of lymph, especially from the medial quadrants of the breast, drains into the parasternal lymph nodes along the internal thoracic vessels.
  • Some lymph from the lower quadrants of the breast passes to the inferior phrenic nodes.
  • It is important to note that lymph from the medial quadrants can cross to the opposite breast.
  • Thus secondary metastases of breast carcinoma can spread to the opposite breast in this way. (Box 3-2-1 and Box 3-2-2)
Thorax > Mammary Gland > Figures
FIGURES
Plate 184: Thorax—Mammary Gland—Lymph Vessels and Nodes of Mammary Gland (sites of metastatic spread of breast carcinoma)
Fig. 3-2-1: Sagittal section through the right breast and underlying chest wall. In this dissection, the glandular structure of the breast cannot be distinguished. (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Edition Mosby, 2005, Fig 2.8, p. 30)
Fig. 3-2-2: Examination of the breast. Performed in a rotary fashion, the entire breast is gently palpated by compression against the chest wall. (From Hansen JT, Lambert DR. Netter's Clinical Anatomy. Elsevier Inc., 2006, p. 303)
Thorax > Mammary Gland > Facts and Hints
FACTS & HINTS

PART A: HIGH-YIELD FACTS
Box 3-2-1: Clinical Points
Examination of the Breast ( Fig. 3-2-2)
  • Clinically the breast is divided into quadrants:
    • UI: upper inner
    • UO: upper outer (includes axillary tail)
    • LI: lower inner
    • LO: lower outer
  • The breast is palpated in a circular fashion, beginning with the nipple and moving outward. The palpation should extend into the axilla to palpate the axillary tails.
  • After palpation of one breast, the other should be palpated in the same way.
  • Examine the skin of the breast for a change in texture or dimpling (peau d'orange sign) and the nipple for retraction, since these signs may indicate an underlying pathology.
  • Box 3-2-2: Clinical Points
    Pathology of the Breast
  • Fibroadenoma: benign tumor, usually a solid and solitary mass that moves easily under the skin. Often painless although sometimes tender on palpation. More common in young women but can occur at any age.
  • Intraductal carcinoma or breast cancer: the commonest type of malignancy in women but can also occur in men. Approximately 50% of cancers develop in the upper quadrant of the breast; metastases from these cancers often spread to the axillary lymph nodes. This malignancy presents as a palpable mass that is hard, immobile and sometimes painful. Additional signs can include bloody or watery nipple discharge if the larger ducts are involved.
  • Gynecomastia: enlargement of the breasts in males because of aging, drug treatment, and changes in the metabolism of sex hormones by the liver.

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